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THE ECONOMIC FEASIBILITY OF A COMMERCIAL, SCALE MANILA
CLAM (Tclpesphi@pinmum) HATCHERY ON VANCOUVER ISLAND
by
William Alistair Struthers
B. Sc. (Hons), Mount AUison University, 1993
PROFESSIONAL PAPER SUBMITTED IN PARTIAL mTLFILMENT
OF THE REQUlREMENTS FOR THE DEGREE OF
MASTER OF AQUACULTURE
in the Department
of
Biological Sciences
O William Alistair Struthers 1997
SIMON FRASER UNIVERSITY
February 1997
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The Manila clam, Tapes philippinanun (Adams and Reeve, MO), supports a valuable
recreationd and commercial fishery dong the West Coast of Canada However, due to
increased market demand and human encroachment, naturai stocks are unable to continue
supporting such a fishery. Depletion of this resource has created an intense interest in
Manila clam mariculture. This has been prompted in part by the British Columbia
govemment's attempts to optimise economic yields from shellfish producing foreshore
leases. Procedures for spawning, Iarval rearing, nursery cultivation, and grow-out have
been proven and are well established.
This paper is an examination of the feasibility of estabtishing a Manila clam hatchery on
Vancouver Island, British Columbia Biological aspects of, culture technology of, and
financial considerations of the proposed project were examined While displaying
sensitivities to downward trends in the price of seed clams and decreased levels of
production, the proposed project is barely financiaily viable at the projected levels of
output. The future of such an enterprise looks promising should the area designated for
clam culture double within the next four to five years, as forecasted by government and
industry projections.
iii
Dedication
With Love
to my
parents,
thanks for watching over me
Tabk of Contents
..
Approval..........................................................................................................................
11
...
Abstract ...........................................................................................................................
iii
Dedication ........................................................................................................................
iv
............................................................................................................
Table of Contents
v ..
Table of Tables................................................................................................................
vil
...
.
.
........................................................................................
vu1
Table of Figures ...................
1.0 Introduction ..............................................................................................................
1
1.1 Clam Fisheries...........................................................................................................
2
1.1.2 British Columbia Clam Fishery .................................................... 5
1.2 History of Clam Culture.........................................
..............7
10
.........................................................................
1.3 Status of Clam Aquaculture
1.3.1 Clam Aquaculture in BC ............................................................... 12
2.0 The Biology of Tapes p h i l i p p i m m .......................................................................
15
2.1 Nomenclature ...............................................................................................
15
2.2 Ecological Requirements ............................. . ........................................
15
2.3 Spawning Cycle ...........................................................................................
17
2.4 k a 1 Development .....................................................................................
19
2.5 Growth ......................................................................................................... 20
2.6 Predation ......................................................................................................
22
2.7 Diseases and Parasites................................................................................
23
2.7.1 Parasites & Symbionts in Mada Clams....................................... 24
2.7.2 Disease Causing Agents in the Genus Tapes ................................ 26
2.8 Research and Development.........................................................................
27
2.8.1 Polyploid Roduction..................................................................... 27
2.8.2 Cryopresewation of Gametes...................
.
............................... 29
................................ 31
3.0 Manila Clam Culture & Husbandry ...................................
3.1 Hatchery Phase ............................................................................................. 31
3.1.1 Water Quality & Hygiene.............................................................. 31
3.1.2 Broodstock Selectioo & Conditioning ......................................... 35
3.1.3 Spawning & Fertilization.......................................................
40
3.1.4 Lama1 Rearing Methods............ .
.
.............
.
.
............................. 43
3.1.5 Metamorphosis and Setting...............................
. .45
3.1.6 Alternative Feed Sources .......................................................... 49
3.1.7 CuUing............ ............................................................................. 51
........................................52
3.1.8 Algal Culture Methods........*..........
.
.
3.2 Nursery Culture............................................................................................ 56
3.3 Grow-Out ..................................................................................................... 60
4.0 The Operating Environment..................................................................................... 62
4.1 The Market ................................................................................................... 62
4.2 Target Market............................................................................................... 62
4.3 Cornpetitors .................................................................................................. 63
4.4 Key Assets and S M s ................................................................................... 64
.
.
.
.
....
.
.
5.0 Proposed Project ........................~.........~...................................................................
64
5.1 System Design.............................................................................................. 64
5.1.1 Permanent Structures ................................................................ 65
5.1.2 HOOC
PIan ...................................................................................... 65
5.2 Water Sources and Filtration........................................................... 1............ 66
5.3 Nursery ...~.....................................................................................................66
6.0 Financiai Analysis .................................................................................................... 67
6.1 Estimate of Capital Expenditures................................................................. 67
6.2 Financial & B iological Assumptions ........................................................... 67
6.3 Pro-Forma Income Statement ...................................................................... 72
6.4 Pro-FormaCash Flow Schedule .................................................................. 72
6.5 Pro-Forma Balance Sheet............................................................................. 76
6.6 Financial Summary .....................
.
.
...................................................... 76
6.7 Sensitivity Analyses ..................................................................................... 79
6.7.1 Disaster Scenario........................................................................... 81
7.0 Eüsk Assessrnent ...................................................................................................... 83
8.0 Surnmary ....................
.
.................~.......~................................................................
86
Bibliography .................................................................................................................... 88
Appendix A .....................
.
........................................................................................... 98
Appendix B ................................................... ........................................................ 103
Appendix C ..................................................... .
.
.
....................................................... 104
Tabie of Tables
...........*...........*...*......3
Table 1. Clam species of global economic importance..........
.
Table 2. Genus and species narnes of the Manila clam.................................................. 16
Table 3 . Prevaience of parasites and symbionts in Manila clams .................................. 24
Table 4. Diseases affecting the genera Tapes,Ruditapes and Venempis ......................26
Table 5 . Prevention and management of bacterial infections .1....................**................
33
Table 6. Critical factors associated with various nursery systems ................................. 57
Table 7. Initial invatment and capital assests scheduie ................................................ 68
Table 8. Annuai depreciation schedule of capital assets ................................................ 70
..............*............73
Table 9. 10 year pro-forma income statement...............
Table 10. Annual operating expenses ......................................................................... 74
Table 11. 10 year pro-forma cash fiow ................................................................
75
Table 12. 10 year pro-fonna balance sheet .................................................................... 77
Table 13. Financial summary......................................................................................... 78
Table 14. Sensitivity anaiysis for changes in seliing pnce............................................. 80
Table 15. Sensitivity andysis for changes in level of production.................................. 80
Table 16. Disaster summary ......................................................................................... 82
Table of Fieures
Fig. 1. Twenty year global landings ............................................................................... 4
Fig. 2. Price per kiIogram of Manila clams.................................................................... 6
Fig.3 . Wild Manila clam hwest................................................................................... 13
Fig.4. Manila clam growth rates ................................................................................... 21
1.0 Introduction
En recent yeacs an increased interest in the culture of marine invertebrates hm bbeen
apparent around the globe (Manzi, 1985; Manzi and Castagna, 1989a; Pillay, 1990).
Increased natural exploitation has resulted in increased market demand, and hence
escalated prices (Manzi and Castagna, 1989a).
Molluscs have traditionaiiy k e n
considered an inexpensive food item. This is no longer the case, especiaiiy in Europe,
where some species are now considered luxury foods. Attention ha k e n focused on
culturing Iow trophic level organisms, with success k i n g observed in oysters, clams,
mussels and scailops. Bivalve moiluscs are particularly enticing due to the fact that food,
spat for gow-out systems, and waste removal may be provided by nature at Lttle or no
cost to the operator (Webber and Riordon, 1977). Clams in particular lend themselves to
commercial mariculture opportunities. Clams support commercial, sport, and subsistence
fisheries, aii of which have seen a decline in natural stocks over the past numkr of years
(Mami, 1985; Manzi and Castagna, 1989a). This deciine in populations is due to a
number of reasons, not the least of which are pollution and overfishing, The resuiting
decline in clam stocks and strong market demand have sparked an intense interest in clam
aquaculture over the past few years.
Along the coasts of North America three species of clams have received much attention
fiom commercial culturalists: the hard clam, Mercenaria mercenaria, distributed dong
the Atlantic coast fiom the Gulf of St. Lawrence to the Gulf of Mexico (Manzi, 1985); the
soft shelled cIarn, Mya arenaria, occuning from Labrador to South Carolina (Manzi and
Castagna, 1989a); and the Manila clam, Tapes philippinarum, found dong the Pacific
coast from British Columbia to California (Quayle and Bourne, 1972; Bourne, 1989). In
North America, wildstock harvests still account for approximately 90% of clam
production (Manzi and Castagna, 1989a). Despite the fact that the technoIogy has k e n
available for nearly two decades, only Iirnited commercial application has thus fu been
apparent, with the majority of effort being concentrated in the research and development
secton ( M a i , 1985).
In an attempt
to achieve p a t e r economic yield from
oyster leases, many British
Columbian oyster growers are turning to Manila clam culture in the previously
undemtilized upper niches of their foreshore lease (Roland and Gubbels, 1990; Heath and
Gubbels, 1993). Manila clam production in British Columbia for 1993 totalled 400
tonnes, with a f m gate value of $1.5 million (Anon., 1996a). As a result of increased
interest, Manila clam production is projected to mach 7,500 tonnes with a resulting value
of $25 million by the year 2000 (Anon., 1995). This trend toward diversification will
bnng with it an increased demand for Manila clam seed. With the exception of two small
scale operations located on Vancouver Island, no large scde commercial hatcheries exist
in British Columbia. M d a clam seed for Vancouver Island is currently suppiied by the
aforementioned operatious and imports fkom the States of Washington or California
(Brian Kingzett, BC SheWxsh Growers Association. personai communication). As a
result, an opportunity exists for a large scale hatchery located on Vancouver Island.
Vancouver Island would be the location of choice, as the majority of Manila clam
growen are located on the island. The purpose of this project is to review current
hatchery technology and assess the economic viability of a Manüa clam hatchery
supplying seed to growers in British Columbia
1.1 Clam Fisheries
The culture of molluscs currently accounts for one third of the total world aquaculture
production, with clams, cockles and arkshells accounting for approximately 22% of total
molluscan production (Anon. 1994; Anon. 1996b). In an attempt io place the global clam
fishery into perspective, Table 1 lists the most commonly fished species of clams, as well
as indicating whether these species are of current or potentid interest to aquaculturalists.
Reasons behind some species not k i n g considered for aquaculture are a lack of
understanding of the complete Life cycle, technical limitations, or low market price or
demand (Boume,1989; Manzi and Castapa, 1989a)- There is, however, some diiculty
in obtaining accurate aquaculture production nurnbers due to inconsistencies in reporting
techniques among various counuies (Anon. 1994). World-wide landings (both cultured
and traditional catches) have slowly nsen from 150 thousand metric tonnes per year in the
early 1960's to an estirnated 1.7 million metric tonnes in 1992 (Fig.1).
Table 1. Clam species of global economic importance (Manzi and Castagna, 1989a;
Anon. 1994).
'spcies name
Common Name Aquacultum Location
conslderation
Anadara subcrenata 'Mogai"clam
Aria spp.
arkshell clams
Arctica islandica
ocean quahog
common cockle
Cardium edule
Corbiculajaponka
Mactra sachalinensis hen clam
hard clam
Mercenana
mercenaria
Meretrix spp.
hard clam
Meretrix lusoria
Japanese hard
clam
"Machanclam
Mesodesma
donacium
Mya arenana
soft shell clam
Panopea generosa geoduck clam
shortneck clams
Paphia spp.
Protothaca sfaminea little neck clam
Protothaca thaca
"Taca" clam
SaXidomus giganteus butter clam
Spisula solidissima surf clam
Tapes philippinarum Manila clam
Y=
yes
no
no
Yes
no
no
Y=
1~ridacnagigas
yes
lgiant clam
Japan, China
Mexico,Korea, Thailand
Canada, USA
Europe
Japan, Korea
Japan, Korea
USA, Canada
YeS
no
no
YeS
Y=
Y=
Y=
lndonesia
Japan, Korea
-
USA, Canada, France, Japan
USA, Canada
Malaysia, Philippines
Canada, USA
Chle, Peru
Canada, USA
Canada, USA
Canada, USA, Japan, Korea
Europe
South Pacific
The most recently available global production statistics are those compiled by the Food
and AgricuIture Organization of the United Nations for 1992. During this year, the
estimated total global aquaculture production of clams (including cockles and arkstiells)
was 765 thousand metric tonnes (Anon., 1994)- Projected global aquaculture production
is expected to reach 1 miilion metric tonnes by the turn of the century, and 2.2 miIlion
metric tonnes by 2025 (Anon., 1996b).
As a result of unrelenting human pressures, seafood products have been turned into an
unsustainable resource. By the yeai 2010, it is predicted that aquaculture wilI produce
upwards of 40% of aiI seafood for human consumption, resulting in greater than half the
value of the global catch (Anon., 1996b). Fish is currentiy the fifth most important
agriculturai product, accounting for 7.5% of totai world-food production, and is relied on
by more than one billion people as a primary source of animal protein (Anon., 1994). Not
surprisingly, world production is currentiy centered around the following big cash
species: shrirnp, salrnon, tilapia, and carp (Anon., 1996b).
1
Figure: 1. Twenty year global clam catches (including cockies and arkshells) (Anon.
1994)
As natural mollusc stocks are depIeted, either as a result of overfishing or human
encroachment, aquaculture is projected to increase production (Anon. 1996b). Totd
world mollusc production in 1992 was 3.5 miilion mefric tonnes (Anon. 1994),
representing 18% of total global aquaculture production. Production can further be
broken down as follows (Anon. 1994):
mussels 1,086,OOO MT
oysters 954,000 MT
clams, cockles and arkshelis 765,000 MT
scallops and pectens 549,000 MT
other moliuscs 147,000 MT.
1.1.2 British Columbia Clam Fisbery
The commercial clam fishery in British Columbia has been in existance since the end of
the 19th century (Quayle and Borne, 1972), and of the over 800 molluscan species
@oume, 1989) occuring off the Pacific coast, only a few are currently of commercial
interest. The five species of clams of most commercial importance are: butter clam (S.
giganteus); littleneck clam (P. staminea); Manila clam (T.philippinarum); razor clam
(Siliqua patula); and geoduck clam (P. generosa) (Schink et al, 1983; Bourne, 1989;
Harbo, 1990). Minor landings of horseclarns (Tresus capax and T. nuttallfi, cockles
(Cfinocardium nutrallrJ, and sofi-shelled clams (M. arenaria) also occur (Bourne, 1989).
Butter clams (S. giganteus) were the mainstay of the British Columbia clam fishery for
the first half of the 2ûth century (Bourne, 1989). Recently, landings have decreased due
to high processing costs and lower market demand.
According to Boume (1989)
reductions in some populations may be attributable to low rec~itmentlevels.
Fig. 2. Landed catch value per kilogram of Manila clams (Anon. 1996c)
Two species of steamer clams are harvested in BC, the native IittIeneck (P. sramineu) and
the Manila clam (T.philippinarum) (Boume, 1989). The native iittleneck occurs siightIy
lower in the intertidal zone than the Manila clam (Schink et al, 1983; Chew, 1989).
Landings of both species were low until a strong market demand for steamer clams during
the mid 1970's created an interest in the commercial harvest of these clams (Bourne,
1989). A strong demand is stiil evident from the landed price per kilogram (Fig. 2),
which continues to rise, no doubt the result of limited wild harvests matched by a strong
market demand. Steamer clams, especially the Manila clam, now constitute the majority
of clam Iandings in the province (Anon. 1996~).
The razor dam (S. patula) fishery consists of a small commercial fishery on the north
coast of the Queen Charlotte Islands, but accounts for less than 100 tonnes per annum.
The majority of this catch is used as bait in the commercial crab fishery (Bourne, 1989)
1.2 =tory of Clam Culture
References to shellfish culture c m be found dating back to 2000 BC in Eastern
civilizations and 400 BC in Greek and Roman periods (Manzi, 1985). Shellfish culture
probably was introduced to North Arnerica by euly European settlers who practised
oyster culture (Manzi and Castagna, 1989a). Clam culture is a f&irIy new activity, as up
untiI recently, natural stocks were abundant enough to supply harvesting needs. It is
thought that a simplified form of clam culture may have been practised by aboriginal
people and early settlers (Manzi and Castagna, 1989a). In this crude f o m of culture,
cIams were harvested from one location and transplanted to a more convenient location
for stonge. Although clam culture has been practised in crude manners for centuries, it
has ody been in the last four decades that the technological breakthroughs that have
ailowed clam culture to enter the commercial realm have been realised (Manzi, 1985;
Chew, 1989; Manzi and Castagna, 1989a). The majority of work done in the clam
aquaculture field bas been conducted on the east Coast of the United States, and focused
on the commerciaUy important species M. mercenaria and M. arenaria. The following
overview of the history of clam culture draws heavily from the discussion by Manzi and
Castagna (1989a).
The first truly successful culture attempt in which a mollusc was manipulated to spawn
was achieved in 1879 by W i a m Brooks. In his experiments, Brooks was able to spawn
oysters, fertilize the eggs, and rear the lame through to metamorphosis (Manzi and
Castagna, l989a).
The first successful atternpts at culturing clams were achieved by William Wells during
the early 1920s (Manzi and Castagna, 1989a). Wells was able to successfully grow
quahogs (M. mercenaria) and the soft clam (M. arenaria), as well as mussels, oysters,
and bay scallops. WelIs' achievements represent the fmt recorded success of clam culture
in North America Wells noticed microscopie animais in the sediment of centrifuged
seawater, which he concluded to be oyster Iarvae- After resuspending the sedirnent in
naturai seawater and fading in attempts to grow hem, Wells obtained oyster garnetes
using the techniques pioneered by Brooks. These garnetes were placed in clarified
seawater and larvae successfully grown to metamorphosis (Manzi and Castagna, 1989a).
Most of the work conducted by Wells focused on oysters, which he was successfully able
grow to market size.
No other work was conducted in this area und the eady 1950's when Victor Loosanoff
renewed interest in bivalve hatchery techniques. Loosanoff pioneered many of the
currenc day hatchery techniques, some of which include:
methods for conditioning
broodstock, the use of thermal shock to induce spawning, the use of unicellular algae as
feed for larvae, and methods for controlling disease within the hatchery (Loosanoff and
Davis, 1963). The techniques pioneered by Loosanoff are often referred to as the Milford
Laboratory techniques (after the US Fish and Wildlife Service in Milford, Connecticut).
The first commercial clam hatchery in North Arnenca was started in Atlantic, Virginia by
Richard Kelly in the late 1950's (Mami and Castagna, 1989a). Kelly used the Milford
techniques, and later modified them by replacing uniceliuIar algal culture with fertilized
and filtered seawater, to culture M. mercenaria. Once set, clams were held in wooden
trays containing beach substrate, and seawater purnped through them. No supplernental
feeding was carried out. Clams were planted to the beach when they had reached a size
of 3 to 4 mm. Survival rates of planted seed are unavailable, however, it is thought
mortality rates were high due to extensive predation. In an attempt to combat predation,
KeIly constructed small stockades of pickets to exclude crabs (Manzi and Castagna,
1989a).
The effectiveness of these anti-predator measures are not reported in the
literature.
- A second commercial hatchery was started by Joseph Glancy in 1959 on Great South Bay
at West SayviIle, New York (Manzi and Castagna, 1989a). This hatchery produced both
clams (M. mercenaria) and oysters (Crassosrrea virginica). Having been a student of
Wells, Glancy adopted both the Milford techniques and those pioneered by his former
teacher. Following some experimentation, the techniques involving uniceIlular aIgal
culture were deemed too costly and complicated, and dropped, Glancy is credited with
developing a low cost method of algal production.
The Glancy method of algal
production involved c l m n g seawater in order to remove unwanted zoopIankton and
di&oms, and aiiowing the remaining phytoplankton to bloom in a greenhouse. Glancy is
viewed as king extremely influentid in the development of the cIam culture industry
(Manzi and Castagna, 1989a). Nearly al1 of the early east coast clam hatcheries started
off using the Glancy method of algal production.
The next advancement in hatchery technology was achieved by the Bluepoints Oyster
Company, of West Sayville, New York. This Company started off using the Glancy
method, but later switched to the production of unicellular algd culture (Manzi and
Castagna, 1989a). The unique aspect of their production was the use of a saltwater well
to supply abiotic water to the hatchery for use in algai culture and larval production.
While a well supply of seawater offered the advantage of k i n g free from bacteria, it
posed the disadvantage of k i n g low in nutrients and dissolved organic matter. As a
result, the addition of nuttients to larval culture was necessary. Simiiar to many east
coast shellfish companies, the Bluepoints Oyster Company cultufed both clams (M.
mercenaria) and oysters (C. virginica).
During this sarne period, several other cornpanies had dso started up commercial scaIe
clam hatcheries, cornbining both the Glancy method and unicellular algae feeding (Manzi
and Castagna, 1989a). These cornpanies are of particular importance due to the ongoing
refining that took place throughout their operation. Of particular note is'the Long Island
Oyster Company of Long IsIand, New York, which incorporated the thermal effluent
from an electricai power generating plant in order to increase the rate of growth of
juveniles ( M m i and Castagna, 1989a). State hatcheries within the U.S. have also played
an important role in the developrnent of clam culture technology.
Many of these
hatcheries were used as research centers, and resulted in a large number of scientifc and
econornic papers conceming clam aquaculture.
Over the last two decades, research has focused on the field grow-out portion of clam
aquaculture and the controlling of costs in this area (Anderson et al, 1982; Chew, 1989;
Spencer et al, 1992). Early attempts at field grow-out involved no forrn of predator
protection and m l t e d in high mortality rates (Chew, 1989). Following the development
of low cost predator netting to reduce mortalities, the commercial scale undertaking of
clam aquaculture became economically feasible. The only remaining problem facing
commercial clam producers was the high degree of mortality associated with planting
seed less than 6 mm in size. Mortality is significady less with seed 8
-
10 mm than
smaller seed (Chew, 1989). As hatcheries cannot afFord to grow clam seed to this size in
an intensive system, fieId nursery systerns have been deve1ope.d in the last decade (Claus,
1981; Manzi, 1985; Manzi and Castagna, 1989a). Several types of nursery methods have
been used, with most operations utilize either an upwelling or downwelling system.
1.3 Status of Chm Aquaculture
As a result of king popular research organisms, due maidy to their ubiquitous nature and
comrnercid importance, a significant amount of information regarding the biology,
environmental requirements and ecologicai interactions of clams is avriilable (Manzi and
Castagna, 1989a). The result of this is that the prognosis for clam aquaculture looks
good, both for North America and British Columbia Despite a good forecast, Manzi and
Castagna (1989a) see the development of cIam aquaculture to be slow and uninspired,
due mainly to the following three constraints: 1) regulatory restrictions, 2) organisrnic or
environmental limitations, and 3) a lack of knowledge in certain areas of clam biology.
These contraints cm further be categorised into bureaucratic and technical limitations,
with regulatory restrictions king classified as the former, and species and knowledge
limitations the latter.
By far the most serious threat
&O aquaculture
in Canada and the US are the regulatory
restrictions imposed by government (Albrecht, 1990; Clayton, 1990; Cockburn, 1990;
Dickson, 1990). Regulations are often in pIace to cover such aspects as species
importation, water and land use, pdution control, and heaIth and safety. In addition,
local authorities may exercise discretion over the grantirtg of aquaculture licences (Manzi
and Castagna, 1989a). The combined mult is ofien a lengthy and fmstrating process to
obtain an aquaculture operating permit. This is often blarned for the lack of initial
investrnent or expansion in the clam aquaculture industry.
Dissatisfaction with
government is also present in the aquaculture industry due to contradictory signals given
by governrnent. On one hand, the lead government agency responsible for aquaculture
wishes to encourage growth and development, only to be met by opposition from another
government agency responsible for such portfolios as environmental issues. Such an air
of frustration has been apparent in the British Columbia aquaculture industry for a
number of years.
Technical constraints to clam aquaculture in British Colubmia include organismic andor
environmental limitations, dong with a lack of knowledge in certain areas. Organismic
restrictions can be overcome to a large extent with proper species and site selection,
factoring in aspects such as predators and hydrological phenomena (e.g. pardytic
shell'fish poisoning) (Borne, 1989).
A lack of information is one which may be overcome through increased CO-operation
within the industry. Manzi and Castagna (1989a) cite limitations in the North American
mollusc industry to be gaps in knowledge pertahing to genetics, nutrition. and disease
and parasite control. Weaknesses in areas such as a general lack of cornprehensive
reviews of literature concerning rnoilusc culture, and a general lack of dernonstration or
pilot facilities were dso noted-
1.3.1 Clam Aquaculture in British Columbia
Clam aquaculture in British Columbia is still in its infancy. The culture potential of
various indigenous clam species was examined by Boume (1989) during the 1970's and
80's. Butter clams were examineci, but slow growth rates (greater than five years) and an
umeliable supply of seed resulted in the termination of the project. The current down
turn in the market for butter clams (G. McClellan, Mac's Oysters Ltd., persona1
communication) is yet another reason preventing the economic success of butter clam
culture. Littleneck culture experiments were also undertaken at the same time the butter
clam trials were k i n g conducted Littleneck clams were better suited for culture due to a
faster growth rate (three to four years). However, seed supply posed a major obstacle to
the development of the industry (Boum, 1989). No hatcheries were established, and
collecting seed from a wiid set would be prohibitively expensive. As a spin off of
littleneck culture research, and fueled by the success demonstrated in Washington State,
Manila clam research was undertaken. Manila clams proved to be the best candidate
species for clam culture in British Columbia due to a fairly fast growth rate (3-4 years),
the commercial availability of seed fiom hatchenes in the United States, and a strong
market demand for the product (Bourne, 1989). Manila clams have since been the main
stay of clam culture in British Columbia
The first clam f m was licenced in 1988, but clam aquaculture did not become official
until 1991, when a joint federal-provincial letter of understanding was s i a e d
(Chettleburgh, 1996). Clam production has increased from 31 tonnes in 1989 to 500
tonnes in 1994, and is projected to reach 7 5 0 tonnes by the year 2000 (Anon., 1995).
There are currently 403 hectares of foreshore designated for clam culture, of which h d f
includes oyster and non-productive ground (B. Kingzett, BC Shellfish Growers
Association, persona1 communication).
The future for clam aquaculture in British
Columbia looks promising, as it appears the wild harvest of Manda clams has plateaued
(Fig. 3), while a strong market demand still remains. It is this gap between demand and
wild harvest that clam aquaculture can fa.
Fig. 3. Wild Manila clam harvests showing toial harvest and total landed value for
British Columbia (Anon., 1996~)
Once peak production is achieved, a properly managed clam farm should be able to yield
2 kg of clams per square meter (23 t/ha) (Chettleburgh, 1996). Most clam farms have not
yet reached this Ievel of production as a result of inexperience. Clam farrns do however
produce half of the wild fishery using only 1/10 of the area (Anon. 1996a). It is estimated
that at full production capacity the clam aquaculture industry wiI1 be able to produce four
times the wild fishery (Chettleburgh, 1996). in cornparison, the wild fishery encompasses
1600 - 3200 hectares of foreshore, with an average yield of 0.1 kg per square meter,
resulting in an annual yield of 1300 tonnes for 1995 (Anon., 1996a). In many areas the
fishery is reduced to tess thm 16 days per year (Chettleburgh, 1996).
2.0 The Biology of Tapes philippinarum
The Manila clam is an exotic species fint introduced to North America through the
importation of Japanese oyster (Crassostreagigas) seed from Japm in the mid 1930's
(Bourne, 1982).
It was f'irst reported in Ladysmith Harbour, BC in 1936, and has
successfully spread northward as far as the Queen Charlotte Islands, British Columbia
(Bourne, 1982), and as far south as Humboldt Bay, California (Chew, 1989). The
accidental introduction is now considered to be beneficial (Bourne, 1982; Chew, 1989),
as this species has found general acceptance as an edible mollusc in British Columbia and
supports both a recreational and commercial fishery, as well as a rising aquaculture
industry.
2.1 Nomenclature
The Manila clam (also known as the Japanese littleneck) belongs to the Venus clam
family, Veneridae. It has appeared under a number of scientific narnes in the Literature
(TabIe 2). The currently accepted name is Tapes philippinam, and as such, will be used
throughout the remainder of this text.
2.2 Ecotogicai Requirements
Manila clams inhabit the mid-to-upper area of the intertidal zone, an area that was not
previously dominated by another species prior to their introduction (Chew, 1989). The
lower Iirnit of the Manila clam over laps with the upper limit of the native littieneck clam
(P. staminea),where it is out competed by the native littleneck (QuayIe and Bourne,
1972; Bourne, 1989), thus shortening its theoretical niche. The vacancy of this upper
niche is thought to be responsible for the rapid spread of this species throughout the Strait
of Georgia (Boume, 1989). The width of the Manila clam zone varies with beach slope;
on steep slopes, only a few meters may be inhabited, whereas on a gently sloping beach,
the width may be as great as 75 m. Manila clams do not occur in sub-tidai areas in
British
TabIe 2. Genus and species narnes of the Manila clam reported in literature (Bourne,
1989; Chew, L989;Ponurovsky and Yakovlev, 1992).
Genus Name
Species Name
Amygdala
ducalis; semidecussata; philippinarum
Paphia
bifirrcara, P. (Venerupis)philippinanun
Protothaca
philippinarum
Ruditapes
philippinarum
Tapes
decussatta; decrcssatus; denticulata;
indica; japonica; philippinarum;
semidecussata; vanegata; violascens;
(Amygdaùa)japonica;(Amygdala)
philippinartun
japonica; philippinam; semidecursata;
(Amygdala)philippinarum; (Rudirapes)
philippinanan
decursata; japonica; philippinarum;
tesseha: ( T u D ~decussata
s~
CoIumbia (Quayle and Boume, 1972). Because of their distribution in the rnid-to-upper
intertidal zone and shallow depths within the substrate (10 cm maximum), the Manila
clam is susceptible to extreme temperatures. Die-offs have been reported during severe
winters (Bourne,1982; Bower, 1992).
Ided substrate composition for Manila clam growth consists of grave1 (less than 25 mm
in diameter), sand, a smdl amount of mud (5%)and sheI1 (Anderson et ai, 1982). Such a
substrate should be stable, and can typically be found in the Pacific Northwest in
sheltered bays or inlets (Schink et al, 1983; Bourne 1989; Chew, 1989). For maximum
survival, the beach should have a slope of 15 to 1 or less. Beaches with dopes greater
than 10 to 1 tend to have poor survivai (Anderson et al, 1982). The optimum interiidal
range for Manila clams is approximately 4 - 9to +2.4 m above mean low water (Quayle
and Bourne, 1972).
Water circulation is probably one of the most important factors affecting clam
productivity on kaches (Anderson et al, 1982; Chew, 1989). Not only does water
circulation bring about the sertlement of new larvae, but it is also responsible for
supplyinp food and oxygen necessary for fast growth and the removal of waste products.
Despite its importance, very littie work has been done regarding water movement in clam
field studies. At best, current speed is given using qualitative measures such as slow,
moderate, or fast (Chew, 1989). The water circulation of an area is also directly
responsible for the substrate deposition, and as such, directly affects clam settlement and
survival by influencing the substrate composition (Williams, 1980; Anderson et al, 1982;
Jaeckle and Manahan, 1992).
.
2.3 Spawniug Cycle
Manila clams in populations off Japan have been found to spawn twice each year (Yasuda
et al, 1954, cited in Chew, 1989). The first spawning occurs in the spring, during the
months of May to July. The second spawning takes place during the late autumn, from
late November to December. Clams have been found to start spawning at shell lengths of
15 mm or less (Chew, 1989). In the Pacific Northwest, the Manila clam has only one
spawning cycle a year from May to September, with the majority of clams spawning
during the warmest parts of June and July (Holland and Chew, 1973; Bourne 1982).
Femaies spawn in smail spurts throughout the summer, whereas maies release a large
portion of garnetes at the beginning of the season, and qu~cklyregenerate to release a
second batch toward the end of the spawning season. In Puget Sound, Washington, clams
were found to have mature gametes at sheil lengths of 5-LO mm, however, spawning was
not usually evident until a shelI Iength of 15-20 mm. A11 individuais over 20 mm
spawned at the end of their first year (HoIland and Chew, 1973). Holland and Chew
(1973) also reported the first instance of hermaphrodism in Manila clams, with one of the
937 clams examined k i n g hemaphroditic. Low levels of hermaphrodism have been
reported for other species of c l m (Chew, 1989). The sex ratios of Manila clams in the
two sites studied by Holland and Chew (1973) were 48% males to 52% females and 44%
males to 56% females, indicati& a fairly uniform occurrence of each sex.
The reproductive cycle of the Manila clam in the Strait of Georgia has k e n studied by
Bourne (1982), and found to be similar to that of the Manila clams occumng in Puget
Sound. Adults were found to be ripe in early June, with spawning taking place in mid-tolate June and continuing until September. Similar to the clams studied in Puget Sound
(Holland and Chew, 1973), females were found to spawn continuously over the summer,
whereas males were able to spawa twice within one season. On the West coast of
Vancouver Island, the reproductive cycle is similar, although somewhat delayed due to
lower water temperatures on this coast, particuIarIy as one proceeds northward. The
minimum water temperature to allow spawning and larval development appears to be 13 150C (Quayle and Bourne, 1972; Bourne, 1982). Manila clams in the most northern
populations have been observed not to spawn dunng sumrners with below normal water
temperatures. It is thought that coder water temperatures have halted the northern
progression of Manila dams (Bourne, 1989).
2.1 Larval Development
Larval development takes approximately two to four weeks before spat faiI occurs
(Quayle and Bourne, 1972).
This is dependant on a number of factors such as
temperature, salinity, food supply and currents. Setting size of the Iarvae is between 190
and 24û pm (Chew, 1989; Jones et al, 1993).
The fertiIized egg (approximately 70 pm) develops into a straight-hinged fiee swimrning
veIiger (90 pm) within 24 hours (Cbew et al, 1987). The veliger stage lasts for
approximately two weeks, during which time the veliger feeds on phytoplankton between
2 to 20 Pm. Following this, the veliger develops into a pediveliger (approximately 200 p
m), possessing both a foot and a velum (Jones et al, 1993). It is at this point that the
larvae begin actively looking for a suita1;le substrate on which to settle. Larvae settie on
the substrate and attach by means of a byssal thread secreted from the byssus pit in the
foot of the clam. This serves to temporarily hold the clam to the substratum before it can
commence digging.
The optimum water temperature for larval development is 23 - 240C (Jones et ai, 1993),
with temperature tolerance limits ranging between O and 360C (Chew, 1989). Water
temperatures in the Strait of Georgia generally do not exceed 15 or 160C during the
warmest months of the summer (Bourne, 1982).
Even though water temperature
fluctuations rnay not be enough to h m Manila clams, extreme substrate temperatures
during either the surnmer or winter may be lethal.
The optimal saiinity for the Manila clam ranges between 24 to 32 ppt, with a tolerance
range of 13.5 to 35 ppt (Chew, 1989). Salinities for Puget Sound range between 28 to 3 1
ppt, and no adverse effects on larvai development have k e n noted (Anderson et al,
1982). No salinity data relating to Manila clams in British Columbia could be found.
However, it is assumed that due to the success of Manila cIams in Georgia Strait and the
similar hydrologicd conditions to Puget Sound, the same sdinity toterances hold true for
Manila c1am.s occurring in British Columbia
2 5 Growtb
Growth in ManiIa c l m s is detennined by measuring winter annuli (the straight-line
distance between the anterior and posterior margins of the annuli). Most Manila clams in
British Columbia have distinct winter annuli (Quayle and Boume, 1972). A great number
of growth studies have k e n reported in the Literature (see Chew, 1989 for a review) with
a high degree of varïabiiity corresponding to annud growth rates. To a large extent, the
race of growth is dependant on temperature. ui his review, Chew (1989) reported on first
year growth rates that varied between 8 mm to upwards of Iegal size (38 mm). Market
size Maniia clams were obtained by Raide et al. (1976) under hatchery conditions, Using
nutrient enriched deep-sea water, with temperatures between 22 and 290C in an
upwelling culture system, market shed (38 mm) cIams were obtained in 10 months from
the 5 mm stage, or 13 mcinctis h m the post-set juvedes. Survival rates of 64 and 65%.
respectively, were reporîed.
Such growth triais represent controiied laboratory
conditions, and, as such, bear little meaning for the commercial aquaculturalist, except to
denote a maximum obtainabIe growth rate under carefully controlled, noncommercialised conditions.
O
1
2
3
4
5
6
7
8
9
10
Age (Years)
Fig. 4. Manila clam growth rates in the Stnit of Georgia (from Quayle and Boume,
1972)
As growth experiments have been conducted on iocal populations of Manila clams
(Quayle and Bourne, 1972). these numbers are of much more pertinence than those
reported from other locales, and should be used as a guide for expected growth rates in
British Columbia (Fig. 4). It is also important to bear in mind that local topography,
hydrological conditions, and geography wili influence growth rates ai a micro-habitat
level (Williams, 1980).
In British Columbia, Manila clams cm attain legal hamestable
size in approximately 3.5 years in the Strait of Georgia; 4 years on the western coast of
Vancouver Island; 5 years in the central coast m a ; and 5.5 years in the Alert Bay area
(Boume, 1982). Growth rates are fastest where water temperature are warmest, and
slowest where temperatures are lowest.
Growth (and survival) rates of clams planted under sorne type of cover are higher than
those planted to an unprotected beach (Anderson et al, 1982; Anon 1990b; Spencer et al,
1992). The higher survival rates are explained through predator exclusion, w hereas a
faster growth rate has been attributed
CO
increased environmentai stability under the
protective covering, and hence an increased energy swings that c m be put toward growth
(Anderson et al, 1982). Exposure is also considered an important factor in the growth
and survivai of clams on the beach. Clams higher in the inteaicial zone tend to be slower
growing than those lower in the intertidal zone, as a result of reduced feeding time in the
upper parts of the beach (Quayle and Bourne, 1972).
2.6 Predation
The Manila clam falls prey to a number of different species, most of which are hard to
eliminate (Quayle and Bourne, 1972; Anderson et al, 1982; Chew, 1989). They can be
controlled to a certain extent through the use of predator exclusion netting, which is now
used extensively throughout the Maniia clam aquaculture industry (Anderson et al, 1982;
Anon. 1990b; Spencer et al, 1992). Predation may be observed directly (as in birds
feeding diiectly on clams), but more often indirectly through damaged and empty shells.
One of the major predators of Manila clams is the moonsnail (Polinices Lewis0 which
preys on clams by drilling a countersunk hole in the umbo of the clam (Anderson et ai,
1982). Most predation is by snails 25-100 mm in sheïï diameter. The presence of
moonsnaiIs is often detected through its circular egg case (Chew, 1989).
Crabs also represent a major predator of Manila dams (Quayle and Bourne, 1972), with
red rock crabs (Cancer productus) king the major predator h m this group. The smaller
graceful crab (C. gracilis) and the shore crab (Hemigrapsus spp.) are minor predators.
Certain species of bottom fish such as the rock sole (Lepidopsetta bilineatea), the English
sole (Parophrys vetulus), the starry flounder (Platichthys steilatus}, and the pile perch
(Rhacochilis vacca) have been known to prey on ,Manila cIams (Quayle and Bourne,
1972; Anderson et ai., 1982; Chew, 1989). These species can be controlled through the
use of predator exclusion netting. Several species of starfish are also thought to prey on
Manila clams, with the sunfiower starfish (Pycnopodia helianthoides) and the mottie star
(Evasterias troschellio being the most serious clam predators (Quayle and Bourne, 1972).
The pink star (Pisaster brevistinus) and the ochre star (P.ochracem) are known as rninor
predators (Chew, 1989). Nearly al1 starfish that have been observed near Manila clam
beds have been at tide levels below the clam occurrence, therefore it is specuhted that the
starfkh probabty do little harm to clam beds (Quayle and Bourne, 1972).
Three species of ducks, the white-winged scoter (Melanina delgandi), the surf scoter (M.
perspicillata), and the American scoter (Oidemia americma) have been reported to feed
on Manila clams (Quayle and Bourne, 1972; Anderson et al, 1982). These birds are often
observed to over winter in hi& numbers in inland marine waters where they feed on
unprotected Manila clam'beds with destructive results. These ducks have not been
directly observed feeding on planteci and protected Manila clam beds, but a small amount
of unobserved predation may occur (Chew, 1989).
2.7 Diseases and Parasites
Of the many criteria that must be considered when culturing an organism, diseases and
parasites rank arnongst the most important.
Associated with the rapid increase in
shellfish aquaculture is an increase in the incidence of disease (Bower et al, 1994). This
is due in part to the development of hatchery-based seed production, remote setting, and
the increased use of non-indigenous species. An increase in the worId-wide transfer of
significant shelifish diseases has aiso been apparent in the past decade. For example,
Bonomia ostreae of oysters (Ostrea edulis) was transferred from North America to
France, and subsequently to the rest of Europe (Bower et al., 1994). This example
typifies the spread of disease through cultured species and is likely to continue unless
prudent quarantine measures are foilowed.
No infectious diseûse agents have been found in Manila clams in British Columbia
(Bower et al., 1992). However, this does net preclude the possibitity that diseases do not
actually occur for the species; it may simply be that none have yet been reported (Elston,
1990). Parasites or symbionts consisting of intracellular bacteria, protozoa, and metazoa
have been observed to be associated with Manila clms in British Columbia Some of the
organisms studied were thought to be enzootic, whereas othen were thought to have
strayed from other molluscan hosts native to British Columbia (Bower et al., 1992).
What follows is a brief sumrnary of those parasitic and symbiotic fauna of the Manila
clam, followed by an overview of diseases known to affect Manila clams and other
species of the genus Tapes. The aim of such an overview is not to claim that such
diseases occur in British Columbia, but to raise awareness of their occurrence, and the
possibility that they may someday occur within Manila clam populations in the province
through accidentai introduction.
2.7.1 Parasites and Symbionts in Maniia Clams
Table 3. Prevalence of parasites and symbionts in Manila clams of British Columbia
(Bower et al., 1992)
~ r e d e n c è ~
-
--
p
p
-
Rickettsia or Chlamydia
Flickettsiaor Chlamydia
Apicomplexan spores
(Nematopsis-like)
Apicomplexa
(Gregm*m4ike)
Apicomplexa
(Coccidia-like)
Tnchodina spp.
Order Rvnchodida
1gill epithelium
1digestiw gland epithelium
moderate
frequent
frequent
ico&tive~issue of gills
-
-
extemal gut epithelium
rare
gut connectk tissue
rare
inner surkce siphon, foot, mantle
gills
frequent
moderate
I
-
-
-
1
.
l~rematodemetacemana ldli connectiw tissue.- diaestiw tract1 moderate
rare
MytiIicoia onentalis
rafe
Pseudomyr'cola ostreae
Pinnaxa faba. P. iittoralis ~eriohervof mantle (commensal1 rare
1
The relationship between the organisms listed in Table 3 and the Manila clam ranges
from symbiosis to parasitism (Bower et al, 1992).
In instances of symbiosis, the
relationship benveen the clam and the associated organism is unclear. The relationship
between Manila clams and Trichodina sp. is thought to border between symbiosis and
parasitism (Bower et ai, 1994). The close relationship observed between Tnchodina and
the gill epithelium is thought to suggest parasitism. Heavy infestations in Europe have
resulted in Trichodina becoming pathogenic, with resulting moctalities.
The same
relationship is thought to be true for Gnffi~llidae-Likenubellaria (Bower et al, 1992). The
benign host-parasite relationship between both Trichodina and turbellaria has led to the
suggestion that they may be enzootic to Manila clams, and that they may have been
introduced into British Columbia with their hosts (Bower et al, 1992). A long observed
association between these parasites and Manila clams without indication of disease
suggests that they are not likely to cause problems in the future.
The remaining parasites observed in Manila clams appear to have strayed from other
molluscan hosts native to British Columbia (Bower et al, 1992). Such is the case with
Nematopsis sp. and the trematode metacercaria. It is thought that the Manila clam
represents an aberrant and hostile host for such parasites, and is a "deade n d host.
The organisms of most concern are the coccidia-like apicomplexan, pea crabs, and
possibly some Trichodina sp., which currently occur in low prevalence, but may cause
problems if they become more abundant (Bower et al, 1992). A higher number of
parasites found in the most northerly populations is thought to be the result of
environmental conditions that are stresshl to the clams, and as a result, the host is more
susceptible to disease and parasitism (Bower et al., 1992).
2.7.2 Diseme Causing Agents in the Genus Tapes
What foilows is a brief surnrnary of the microorgmisms and parasites that are reported to
cause diseses in clams, with pxticular attention given to the genera Tapes, Wrdirapes,
and Venerupis. The objective of this overview is not to claim that al1 such organisrns are
of threat to Manila clam populations in British Columbia, but simply to raise awareness
of exotic diseases. A full synopsis of these diseases is given in Appendix A.
Of particular interest to commercial hatcheries was the isolation of a species of Vibrio,
specific to clams of the genus Tapes. The isolated Vibrio species is referred to as VTP,
and displays an affinity to K marinus (Nicolas et al., 1992). The disease first appeared in
a French commercial hatchery in 1986, resulting in a near complete mortality of the
-
larvae, and between 30 50% mortality of postlmae. This strain of Vibrio had no effect
on oyster larvae that were mixed in with the Manila clam larvae.
Table 4. Diseases a€fecting the genera Tapes, Rudirapes and Venencpis (Bower et al,
1994; Pillard et al., 1994)
Scientific Name
Organisms belonging to the Rickettsiales
Cytophaga-like bacteria (CLB)
Vibflo sp.; M o P l isolate
Vibrio anguillarvm; V. alghoiyticus
Perkinsus atlanticus; Perkiisus sp.
Nematopsis vene&N ustrearum and other Porosporidae
Haplospondium tapetis
Sphenophyra dosiniae; S. cardii
Trichondina spp.
Rhabdocoela of the famiiy Graffillidae
Various species of the Digenea family
Myülicola intesthalis (Copepoda)
Mflicola orientalis (Copepoda)
Pinnotheres son. (Decaaoda: Pinnothendad
Common Name
Rickettsia-like and Chlamydia-like organisr
Hinge ligament disease of juveniles
Brown ring disease
Larval vibriosis or Bacillary necrosis
Clam Perkinsus disease
Parasitism by gregarines
Haplosporidian infection of clams
Sphenophyra-like ciliates
Gill trichodinids
Turbellaria of clams
Trematode metacercarial infection
M~d11icoladisease; Red w o n disease
Mytiicola parasitism; Red worm
Ovster crab. Pea crab
2.8 Research and Development
Two areas of research with possible ramifications to the clam aquaculture industry are the
use of polyploids and the cryopresewation of gametes. Each of these areas will be briefly
eximined to present an overview of the possible future course of industry directed
research.
2.8.1 Polyploid Production
In order to maximise the culture potential of fish and shellfish, research has been directed
toward the production of polyploid animais (Newkirk, 1980; Humphrey and Crenshaw,
1989; Beaumont and Fairbrother, 1991). Following much interest with the use of
triploids for salmonid culture (Benfey, 1996). moliusc research is following the same line
of inquiry. The premise behind polyploidy is that functiond gamete production is
suppressed in polyploids due to a failure of chromosomes in their gametes to pair during
meiosis. The resulting individual is expected to be sterile (Ekaratne and Davenport,
1993). Reasons behind the genetic manipulation and creation of polyploid individuals are
two-fold. When rapidly growing, non-native species are considered for aquaculture, the
use of sterile polyploid individuals can lead to a commercial success through the
avoidance of escapees establishing wild populations and competing with native species.
Polyploid individuds would also be unable to hybridise with native species of the same
genus. Such concems are especiaily valid in areas such as the United Kingdom, where
the introduced Manila clam could possibly compete or hybrîdise with the native T.
deeussatus
(Ekaratne and Daveport, 1993; Utting and Child, 1994). Energy otherwise
destined for gametogenesis is put toward somatic growth, thereby enhancing growth rates
in polyploid individuals (Humphrey and Crenshaw, 1989). In polyploid work conducted
using oysters (Cmsostrea spp.) the lack of reproductive tissue contributed to greater
customer acceptance due to a greater visual anractiveness and improved fiavour
(Beaumont and Fairbrother, 1991). Further, mortdity may b e increased during and
immediately following the spawning period (Humphrey and Crenshaw, L989). Tripioid
individuds would not suffer this loss, thereby increasing the profits to the commercial
culturaiist.
Initial work involving the production of polyploid molluscs for the aquaculture indushy
was carried out on oysters (C. virginica) with the intent of producing an oyster that could
be marketed year round (Stanley et al., 1981). During the summer the meat quality of
triploid oysten was maintained (as a result of reduced gonadal development), while their
diploid counterparts suffered decreased meat quality. Trials have been conducted on
Manila clams (Beaumont and Contaris, 1988) with the intent of reducing gonadal growth,
while at the same time ùicreasing somatic growth. This change in growth pattern would
help to improve meat quality and reduce age at harvesting.
Methods of inducing
polyploidy (mainly triploidy) include subjecting the fertilized egg (10 minutes postfeailization) to thermal shock (Gosling and Nolan. l989), hydrostatic pressure (Chaiton
and Allen, 1985), cytochalasin B (Stanley et al., 1981). or to electricd fields (Cadoret,
1992). Thus far, no method has been successfbl in achieving 1 0 % ûiploidy. The only
known method that results in total triploid production is crossing a diploid with a
tetraploid (Beaumont and Fairbrother, 1991). In light of this, research has been directed
toward the production of tetraploid adults using cytochalasin B. Judging from the results
of Diter and Du@ (1990), the use of cytochalasin B to produce tetraploid adults seems
inviable for Manila clams. In their experiments. survival to the D-lard stage was poor,
and no tetraploids were found at the Cmonth-old spat stage.
Cytochaiasin B now seems to be the method of choice for establishing triploidy. In eggs
treated with cytochalasin B. suMval to the D-lava (or straïght hinge larva stage) was
45% (expressed as a percentage of initial egg numbers), compared to 67% sumival in
diploid controls (Utting and Child 1994). Similar results were obtained for triploid trials
of T. dursarus (Ne11 et al., 1995). Survivai following the D-lana stage was similar for
both diploids and triploids (Utting and Child, 1994). Utting and Child have suggested
that in order to guarantee a high percentage of triploid seed, at lem 70% of treated eggs
mnst develop as uiploids, and survival to the D-larva stage should exceed 55%. Ne11 e t
al. (1995) had an overail mean survival to metamorphosis of 18.5%. This is considembly
lower than the rate suggested by Utting and Child (1994). However, this level of survivai
rnay be acceptable if the possible benefits of increased meat yield or reduced age at
harvest exist The amount of time broodstock are conditioned and the type of diet fed
also influences the success of tnploid induction in eggs treated with cytochaiasin B
(Utting and Doyou, 1992).
Thus far, ail clam triploid studies have been conducted in small scale laboratory
operations. No analyses have been conducted to assess the economic impact on larger,
full scale operations, as is the case with the current anaiysis of using ail female or triploid
stock for AtIantic saimon culture in British Columbia (Ludwig, 1996; Egan, 1996). There
is a strong possibility that the costs of using tripIoid clams rnay exceed the benefits, as the
profitability margin of most clam aquaculture operations is fairIy low (Roland and
Gubbels, 1990; Heath and Gubbels, 1993). The increased cost of using triploid seed may
tum the operation into an unviable venture.
2.8.2 Cryopreservationof Gametes
Limited work has k n conducted on the cryopreservation of Manila clam spenn, but an
appreciable amount of work has been directed toward the cryopreservation of
spermatozoa of several Crassostrea species (Yankson and Moyse, 1991). The driving
force behind this area of investigation has been the possibility that preserved garnetes
could act as a readily accessible source for hatchery rearing, thereby eliminating the need
for the time consuming and expensive process of conditioning broodstock.
Cryopreservation could also preserve valuable genetic strains. This could increase the
breeding potential for such vduable traits as npid growth, increrised disease cesistance,
and better meat quality.
Yankson and Moyse (199 1) have demonstrated the
cryopreservation of oyster spenn to be possible, and have sugested that storage in liquid
nitrogen at - 196OC could have widesprerid use in the oyster culture industry. Sperm were
stored for as long as seven months, and produced a lama1 yield of 18%. Trials conducted
with T.philippinarum have demonstmted the ability to preserve both ernbryos and D-
larval stages (Utting, 1993).
3.0 & I d aClam Culture and Husbandry
In order to gain a-greaterappreciation of the project at hand, an overview of clam culture
techniques follows. By mems of this technical overview. it is hoped that the proposed
project will become more cornprehensible, and the position of a hatchery and the role it
plays will be illustrated in the hierarchy of clam aquaculture. The culture of clams c m be
broken into three distinct phases: hatchery, nursery, and grow-out Each phase becomes
less intensive, and thetefore less technical.
3.1 The Hatchery Phase
As the second half of this document deais with the financial aspects of the hatchery
phase, technical considerations will be examined in this section. The hatchery phase c m
further be subdivided into the foilowing areas: water quality and hygiene, broodstock
selection and conditioning, spawning and fertilisation, algal culture methods, larval
rearing methods, metamorphosis and seaing.
3.1.1 Water Quality a d Hygiene
The water used during the conditioning of broodstock and subsequent raising of larvae
m u t be of sufficiently hi@
quality and free from toxins (see Appendix B for the
biophysical criteria of Manila clam culture). thereby avoiding the problems of slow
growth and mortality. Water quaüty is variable between hatchery sites and is often
implicated in the resulting problems or subsequent failure of a hatchery (Chew et al,
1987). The development of early larval stages is extremely delicate (Chew, 1989). and is
frequently impeded by adverse water conditions. Such conditions can either be man-
made or naturdly occurring, and can include pollutants, toxins leached from sediments,
high turbidity, and dense phytoplankton Wooms (Utting and Helm, 1985). Uning and
Helm (1985) aiso noted that water quality varied seasonally. Reduced larval growth was
corretated to increased minerd content and fine particdate rnatter input, which varied
according to the arnount of freshwater mn-off present.
Such conditions are usually
present during spring and heavy penods of nin. In addition, following the collapse of the
spring diatom bloom, water qudicy has been shown to deteiiorate. Poor areas are usuaily
sites of hi& primary productivity or uncontrolled low sdinities for prolonged p e n d s of
time (Chew et al, 1987).
Within bivaIve hatcheries, the most cornmon problem
associated with poor water quality is Mure of Iarvae to develop to the straight-hinged, Dshaped veliger stage (Jones et al, 1993).
To avoid any of the above rnentioned problems, the water source should be as far
removed as possible from any source of contamination. The intake should be piaced
below the surface to avoid salinity fluctuations, and to avoid any floating contaminants,
such as plastics or petrochemicals. The water intake may be positioned at one of two
depths: above or below the thermocline. Each position has its own advantages and
disadvantages (Jones et al, 1993). By positioning the intake below the thermocline, the
water tends to have increased clarity (due to a lower algal concentration), a more stable
salinity, fewer bacteria, and less chance of toxic contamination. Water from this area
possesses the disadvantage of having fewer natural nutrients and a lower temperature,
both of which contribute to higher production costs in the hatchery. Ideally, the hatchery
should have access to both deep and shalIow water, and be able to switch accordingly, as
the water quality from each source area changes (Jones et ai, 1993).
The improvement of sea water quality has been examined by Utting and Helm (1985). In
their experiments, water was pre-treated with the addition of various chemicals. The
addition of ethylenediaminetetraacetic acid (EDTA) at 1 mgil was found to significantiy
increase Iarvai growth. The cost of such a pre-treatment was not examined, but it is likely
that at the concentrations suggested by Utting and Helm (1985), costs may becorne
prohibitively high. If water is taken from a good quality source as suggested above, pretreatment of the water should not be necessary.
Incoming water should be filtered through a series of filters, the srnailest of which is
generaily 5 - 10 p n in size. The first filter is usuaily a sand filter that filters out large
particulate matter, foIIowed by filtration through cartridge filters, at which point water
empties into a reservoir or the larval rearing tanks (Chew et ai. 1987; Jones et al, 1993).
Some hatcheries may stedise the filtered water with ultraviolet or ozone. Excessive
amounts of particutate matter in the source watir can iead to problems such as filter
blockage.
Along with the care that must go into site selection and water quality control, serious
attention must be paid to the prevention and management of bacterial infections within
the hatchery. The utrnost cleanliness and conscientious management of the water source
has been emphasised by Chew et al (1987). Improper management of the hatchery water
supply can lead to extremely senous problems, and in extreme cases, the complete shutdown and sterilisation of the hatchery may be necessary. Severai points regarding the
prevention and management of bacterial infections withh hatchery situations are
discussed by Elston (1984) and summarised in Table 5.
Table 5. Prevention management of infectious diseases withïin the hatchery (Elston, 1980
1Prevention and Management of Bacterial Infections
t
Maintain absence or low levels of vibrios in the system (water column and
surfaces)
- use appropriate degree of water filtration
- maintain hygiene of system surfaces
- use appropriate frequency of water changes
Isolate infected stocks and associated equipment at Fust sign of clinical disease
Discard infected stocks and sterilise equipment
Identify source of infectious organisms, and modify and clean system
According to Elston (1984), the appearance of infectious animai diseases under intensive
conditions is typical in the development of hi& density husbmdry of any species.
infectious diseases rnay be classified into two categorïes: 1) opportunistic pathogens
which rnay be present in the environment at certain tirnes, and 2) highiy host specific
pathogens which are frequently obligate intracellular pathogens. Pathogens rnay enter a
hatchery via three possible routes: 1) the seawater source, 2) the brwdstock, and 3) the
aIgai food stock (Elston, 1984; Elston, 1990).
Bacterial diseases of lamal and juvenile moiluscs are the most important diseases caused
by opportunistic bacteria. Of the bacterial diseases known to infect bivaive mohscs,
vibriosis is more significant and costly han any similar diseases in larval molIuscs
(Elston, 1984; Elston 1990). Bacterial growth associated with the surface of the shel has
been suggested to retard shell growth and calcium deposition Elston et ai, 1982). As a
result, the management of the rnicrobiai composition of the culture system &ring
metamorphosis and early post-metamorphic stages is essentiai to successful motlusc
culture. The control of surface-coating bacteria can be achieved by the culturalist through
a number of means. Filtration of incorning water to remove particulate matter, onto
which bacteria may be attached, should help reduce bacterial numbers (Chew et al, 1987).
Hygienic mesures such as mechanical cleaning and sterilisation of water Lines and
culture apparatus with a solution of 53 ppm sodium hypochlorite are adequate for
. practical
sterilisation (Elston, 1984). The frequency of cleaning will depend on factors
such as temperature, organic loading, and feeding levels. Bacterial populations which
establish themselves on the shells of juveniles may be removed with a treatment of dilute
sodium hypochlorite. A 1 minute bath in 10 ppm sodium hypochlorite folowed by a
seawater rime should reduce surface residing bacteria (Elston et al, 1982).
the summer months, and hence increased survival during the colder winter rnonths.
Gametes are produced by conditioning the broodstock, a relativeiy simple process of
taking the animais from their natural environment and placing them in w m e r water thrit
is gradually increased to spawning temperature (Loosanoff and Davis, 1963). As a result,
gametogenesis and gamete maturation are accelerated, and mature adults can be produced
before naturd populations start their sexud development.
This ailows bivalves in
spawning condition to be made available year round.
Broodstock are generally maintained in 200 to 2,500 litre fibreglas containers through
which unfiltered, heated (18 - 22OC) seawater is added (Hurley et al, 1987; Jones et al,
1993). Conditionhg containers can be either flow through or static. Flow through
systems should be maintained with a w&te water flow of 1 liue per minute (Utting,
1993). Static water conditioning systems offer several advaniages over flow through
systems: ease of monitoring to determine whether an unintentional spawning has taken
place; ease of maintaining a constant temperature; and a more easily monitored aigal
consumption rate (Jones et al, 1993). Due to the fact that tanks must be cleaned and
stedised on a regular b a i s (every two to three days), a complete change of water musc be
undertaken, therefore the static system offers somewhat of an advantage over the flow
through systems.
Broodstock are gradually conditioned over a period of time in which the temperature is
slowly raised (approximately loîfday) to the desired level (Loosanoff and Davis, 1963).
In the hatchery c m n t l y producing Manila clam seed on Vancouver Island, the optimum
temperature of the conditioning system is 180C (Jones et al, 1993). This temperature is
achieved by slowly increasing the temperature of arnbient seawater over the span of
approximately one week.
Care must be taken during the winter months when the
temperature difference between ambient and conditioning rempenture is greatest, to
avoid unnecessady stressing the clams (Loosanoff and Davis, 1963; Chew et ai, 1987).
The Iength of time required to condition broodstock varies with season, and hence the
natutai state of broodstock gametogenesis (Chew, 1989). During the winter months
(when the dams are out of their natural reproductive cycle), conditioning is usudly
canied out over a 6 to 9 week period, whereas little or no conditioning may be required
during the summer (Jones et al, 1993), when gonads are naturaily ripe- Care must be
taken to ensure that the broodstock is fully conditioned, as it has been s h o w by Lannan
(1980) that lamal survival approaches a maximum when gametes from optimaily
conditioned parents are united under optimal environmentai conditions.
Suggested literature values for stocking densities of conditioning broodstock Vary
-
considerably. Utting (1993) suggests a density of approximately 50 animals of 20 25 g
live weight per 200 1 tank for a flow through system, while Chew et ai (1987) suggest a
much lower stocking density of one to two animals per 50 1 of water for static water
systems. Clams may be conditioned with or without a substrate, as both rnethods have
been reported to yield successful conditioning. Neither treatrnent has been shown to be
better than the other (Jones et al, 1993). Should a closer examination of conditioning
with or without substrates be undertaken, it is likely that those individuals conditioned in
sand substrates will perform better than those conditioned without a substrate. The
reason for this k i n g an increase in energy savings as a result of the substrate pressing
closed the valves of the clams. Those individuals lacking a substrate would have to
expend additionai energy to close their valves.
A rnixed algal diet consisting of Tetraselmis suecica, Skeletmema costatwn and
Thalassiosira pseuàonana
- Clone 3H should be fed to broodstock (Chew et al,
1987;
Utting, 1993). Jones et ai (1993) reported feeding broodstock with the foIlowin,o cultured
species: Thalassiosira pseudonana - Clone 3H, Nunnochloropsis oculata, Chaetoceros
gracilis, Tahitian isochrysis and lsochrysis galbana. The feeding system was set up to
feed the broodstock approximateiy 1 litre per hdf kilogram of clam biomass per hour. It
has been noted that this feeding rate may at tirnes result in the addition of too much food
with an increased production of pseudofeces, but this is outweighed by a potentiaüy
slower conditioning rate if food levels are too low. Additional feeding regimes are also
noted: feeding at 6% of dry meat weight per day (Utting, 1993; Laing and LopezAlvarado, 1994); feeding at 2 litres/animai/day with an aigal concentration of 2 x 106
ceIls/rnl (Chew et ai, 1987); and sea water enriched with S. costatum at a rate of 800
&min resulting in a mean concentration of 2.74 x 105 celIsmil with gentle aeration
(Mann,1979). Alternatively, broodstock diets may consist of seawater enriched with
agricultural fertilizers (Spencer et al, 1986) or be drawn from natural phytoplankton
blooms in large outdoor pools (Eldm et al, 1991). These last two alternatives offer the
advantage of k i n g cheaper than monospecific aigd cultures, however, less control over
species composition results. The introduction of unwanted zooplankton into the system
may also be a problem. The use of specific diets alIows for optimum conditioning
through the selective addition of nutrients required for garnetogenesis (Lannan, 1980;
Utting, 1993). Triais carried out by Utting (1993) have shown diet quality to be
important for maintaining and improving dry rneat weight of adults, dong with a resultant
increase in fecundity. The results of Jones et al (1993) would be most applicable to the
project at hand, as their trials were conducted on the east coast of Vancouver Island.
The effect of diet on broodstock condition and subsequent growth and survival of bivalve
larvae has been shown to be important (Langton et d, 1977; Lee and Heffeman, 199 1;
Utting, 1993; Laing and Lopez-Alvarado, 1994). If broodstock are not cultured under
optimum conditions, then insuficient amounts of nutrients may be transferred to eggs.
Such was the case shown in a snidy with eggs of Crmsastrea virguiica and Mercenaria
mercenaria. In a snidy by Lee and Heffernan (199l), high concentrations of triglycerides
and lipovitellins (high density lipoproteins found within the egg) were required for proper
embryo development and Imd growth.
Recently. research has been directed toward the use of dried d g d diets for replacing live
algal diets. The space, time, and technical expertise required to produce live algal feeds
at the appropriate volumes aii increase the cost of the final product. Algal culture may
account for upwards of 30% of overall production costs (Adams et al, 1991; Utting, 1993;
Laing and Lopez-Alvarado, 1994). In experiments camed out by Laing and LopezAlvarado (1994) investigating the effects of dried dgal diets on conditioning and
fecundity, it was shown that dried diets resulted in higher carbohydrate levels in
broodstock clams. Lipid reserves were higher in clams fed live diets than those fed dned
diets, thus resulting in increased fecundity. It was postulated that viable eggs require a
minimum lipid content, and therefore females with lower lipid reserves compensate by
releasing fewer eggs. Total lipid content may therefore be used to give some indication
regarding the fecundity of a broodstock population. Utting (1993) examined mixed diets
consisting of spray-dried algae and live algae.
The most successful combination
consisted of 70% spray-dried Tetraselmis and 30% live Skeletunema. The fecundity of
clams fed this diet was the same as those fed a 70:30 ratio of live species. The cost of a
spray-dried diet is 30%of the cost of a live algal diet (Utting. 1993). Dried algae also has
the advantage of a less variable biochemical composition (Laing and Lopez-Aivarado,
1994).
The qudity of live diets and dried diets used for broodstock conditioning versus larval
rearing was briefly examined by Laing and Lopez-Alvarado (1994). Live diets tested as
juvenile feed showed a wide range of nutritional quality, and ranked as follows in
decreasing nutritiond value: Sketeronema costatum, Terraselmis suecica and Dunaliella
rertiolecra. No such differences in nutritiond value were apparent when these diets were
fed as broodstock diets. The difference in nuuitlond quality is thought to be the result of
polyunsaturated fatty acid (PUFA)content within the algae. It is believed that adult
clams have the ability to synthesize the PUFAs they require through the elongation and
desaturation of shorter chah faîty acid precursors (Utting and Doyou, 1992; Laing and
Lopez-Alvarado, 1994). At present, more work is needed to fully understand the use of
dried algal diets in both broodstock conditioning and Iarval rearing.
3.1.3 Spawning and Ferüiization
To detexmine the gonadal condition of the broodstock, an animal must be sacrificed for
examination of the-gonad (Jones et ai, 1993). The gonadai tissue is cut, foiiowing which
an examination of the tissue ensues. During this examination, the softness and fuiiness of
the tissue is noted. A microscopie examination of the gametes is conducted to assess the
development of eggs and motility of sperrn. It should be noted that males tend to
condition faster than females, therefore fully ripe maies do not necessarily indicate a
population ready to spawn (Chew et al, 1987). In oysters (Crassostrea gigas) it was
demonstrated (Lannan et ai, 1980) that when spawning took place before the optimum
conditioning period had k e n reached, spawning resulted in substantiai garnete release.
However, a large proportion of the gametes were not fully ripe. Similady, if broodstock
was conditioned for too long a period, an increasing proportion of gametes were non-
viable and had started to deteriorate. The optimal window for conditioning, as defined by
Lannan et al (1980), was the conditioning p e r d during which the gonadai index of the
spawning population was increasing, but had not reached a plateau.
This index is
quantified by counting oocytes and ova in the ovary. The gonadal index is then
calculated as the ratio of ova to the sum of ova plus myctes. In males, the gonadal index
is calculated by comparing the cross sectional area of the portion of the gonad fiiled with
sperm to the total cross sectional area of the gonad (Lannan, 1980).
Once Fully conditioned, thé broodstock must be induced to spawn. Spawning is usudly
induced ttirough thermal manipulation (Loosanoff and Davis, 1963). The first step is to
feed the broodstock heavily (3.5 x 1o6 cellsld of T.preudonana or 14 x 106 cellsfml N.
oculara) at 180C, foIlowing which the clams are allowed to cIear the water of a1ga.e.
Spawning troughs are drained and filled with warm water (25O - 300C) and gonadal
extract (eggs or sperm) is added in order to bring about spawning (Chew et al, 1987). If
after 20 minutes spawning has not commenced, the tanks shouId be drained and fflled
with water at lWC, followed by thermal manipulation and the further addition of gonadal
extrâct.
Should the clams not spawn after this attempt, the clams are not fully
conditioaed (Jones et ai, 1993). Spawning can take up to 2 hours to complete, with males
spawning fmt. The presence of gametes stimulates other clams to commence spawning
(Loosanoff and Davis, 1963). An alternate method to thermal manipulation consists of
placing the broodstock in shallow trays and exchanging the water every 15 minutes using
altemating temperatures of 2OOC and 300C (Chew et ai, 1987). The addition of a 10-3 M
serotonin solution following thermal manipulation has also been shown to induce
spawning (NeU et al, 1995). As serotonin is currently king used in medicai studies of
the hurnan nervous system, the potential hazard to human heaIth must be further assessed
before its routine use in hatchery settings becomes cornmonplace.
-
Numerous methods of spawning exist, including mass spawning, slip spawning,
segregated spawning, and semi-controlled spawning (Jones et al, 1993). Mass spawning,
as the name implies, simply entails allowing al1 of the animais to spawn at once. This is
the simpIest method of collecting eggs and sperm, however, the problem of polyspermy is
often encountered (Jones et al, 1993). This occurs when the sperrn to egg ratio is too
high, and subsequent larval development is affected. Mass spawning in containers may
also prove to be disadvantageous in that there is no way of knowing how many (or which)
parents contribute to the spawning (Hadley, 1993). This has the disadvantage of
decreasing genetic variability. In süip spawning, the clrims are opened and the sex
deterrnined, after which the clams are stripped of their gametes. Eggs are usually washed
and retained in a bucket prior to fertilizaîion.
This method has not proven to be
especidly successful with ManiIa clams (Jones et ai, 1993)- A segregated spawning
involves the quick assessrnent of sex as the clams begin to spawn. The clams are then
allowed to spawn in separate containers and the gametes mixed at the correct ratio for
fertilization. This method has proven to be time consuming, but successful (Chew et al,
1987; Jones et ai, 1993). Spawning in individual containers and equaiising the number of
gametes from the different spawners will ensure that ail parents have a reasonable chance
at contributing to the genetic pool ( H d e y , 1993). A semi-controlied spawning is fairly
similar to a mass spawning, however, at the commencement of spawning, some of the
males are removed to reduce to sperm to egg ratio (Robinson and Breese, 1984). The
water from the spawning trough is ailowed to flow through to the larval rearing tank, as
water from the spawning trough is replaced, thus, the whole system resembles a flow
through system. This method has k e n found to require a minimai amount of effort, yet at
the same time producing high rates of fertilization (Jones et al, 1993).
In order to ensure a high proportion of normal and healthy Iarvae, optimal conditions
must be present (Robinson and Breese, 1984; Chew et al, 1987; Jones et al, 1993; Utting,
1993). Fertilization should take place with a spenn to egg ratio of 10: 1, and with a
temperature range of 230 to 280C in a static water tank. A sperm to egg ratio of 10: 1 is
required for the proper fertilization of eggs and a consistent production of high quality
larvae (Chew et ai, 1987). Higher sperm to egg ratios produce polyspermy, while lower
ratios result in unfertilized oocytes. Should ternperanires drop below 230C fertilization
rates drop significantly, whereas if they are too high, gametes are destroyed and bacterid
growth is promoted (Clotteau and Dubé, 1993; Jones et ai, 1993)- In work conducted by
Clotteau and Dubé (1993) pH was found to affect the fertilization success of surf dams
(Spisula solidissima). Fertilization was greatly reduced below pH 7.5 and totdly
inhibited below 6.0. Alkaline pHs were found to have no adverse effects until 10.5. No
work relating to pH effects on Manila clams couid be found, however, it is not unlikely
that the sarne generd trends may hold me. If such is the case, then it would be wise to
maintain the pH of seawater at its nomal value of 7.8 for the fertilization of eggs.
Once fertilization has occurred, development to D-straight hinge stage is dependent on
temperature and density (Robinson and Breese, 1984). At 240C, the D-stage is usually
achieved &er 24 hours (Jones et ai, 1993). Development tirne to the D-stage is doubled
to 48 hours when the temperature is lowered to 18OC (Robinson and Breese, 1984). It is
desirable to culture the embryos at the highest possible temperame to ensure the fastest
possible development.
3.1.4 Larval Rearing Methods
The optimal temperature for rearing larval Manila clams is 230C, although the larvae can
tolerate temperatures within the range of 14O to 280C (Rucide et al, 1976; Robinson and
Breese, 1984; Hadley, 1993; Jones et al, 1993). Temperatures above and below this range
result in death. High temperatures are deaimental in that they invite bacterial growth
within the larvai rearing environment. Larvae have also been shown to be tolerant of
salinity ranges of 15 to 3@%0, with the optimal range being 20
- 30%0
(Robinson and
Breese, 1984). Salinities below 15460 did not result in survivai to metamorphosis.
Optimum larval rearing conditions therefore consist of a salinity range between 20 to
30%~and a temperature between 230 to 2SOC.
L m d rewing tanks utilizing a flow through system enabIe higher densities of l m a e to
be cultured than in static systems (Chew et al, 1987). Using a flow h u g h system, the
number of larme in a 4,000 litre rearing tank cm be increased considerably (Jones et al,
1993). The disadvantage of a flow through systern is that it requires more maintenance
than its static water counterpart (Le. daily cieanings to minimize bacterid growth). The
outflow screen in a fiow through tank must be carefully monitored and cleaned daily to
ensure that larvae do not block the filter and cause ovediow problcms (Jones et al, 1993).
A series of progressively larger screens may be used as the Iarvae increase in size. This is
advantageous in that larger screens are less likely to experience clogging problems, and at
the same time can more easily accommodate the required water flow. The infiow pipe
should carry preheated water (23O-250C) and freshly cultured algae (approximately 10 to
-
20 thousand cells per miliilitre). Larvae are typicdy raised at a density of 2 5 larvae per
millilitre, although a density of 10 larvae per rniiliiitre has been successfui. It thought
however, that higher densities resuIt in stressful conditions, and therefore increased larvai
mortalities (Jones et ai, 1993).
Larval feeding c m be useful as an indicator for a number of factors to which the larvae
are sensitive, the most important of which incIude water quality, temperature, and density
(Chew et ai, 1987). Larvae not clearing the water can be an indicator of a problem in any
one of these areas. Larval feeding rates should be monitored on an individuai tank basis,
and should generally be fed at a rate of 30 to 50 thousand algal cells per miliilitre (Jones
et al, 1993).
Growth at different l a r d densities under optimal conditions of salinity and temperature
have been shown to be largely a function of food supply (Helm and Millican, 1977). A
more frequent changing of the culture medium in an attempt to make more food available
was shown to be ineffective at promoting improved growth. The addition of sufficient
Food on the days between water changes to make up for that removed from suspension
during the previous 24 hours improved growth.
Larvae stiould be fed the smaller dgal species first, followed by a progressive increase in
ce11 size as growth progresses (Chew et al, 1987; Jones et al, 1993; Utting, 1993). First
feeding should take place on the second day in the larvd rearing tank, with food being
available to the D-land stage (Robinson and Breese, 1984). The first feeding should
consist of the smaller fiagellates, in particular, Nannochloropsis oculata, Tahitian
isochrysis, Isochrysis galbana, and Chaetoceros calcitram (a s m d diatom). The larger
diatoms ThuZassiosira p s e u d o m (Clone 3 H ) and C. gracilis should be added as the
larval approach 150 Fm (Jones et al, 1993)-
3-15 Metamorphosis and Setting
Pediveligers are generally ready to set when they are approximately 150 pm in length,
however, this has been found to range in size from 130 to 165 prn (Jones et al, 1993).
The length of time to metamorphosis has been demonstrated to be dependent on
temperature and salinity (Robinson and Breese, 1984). At 250C and 20-30%0 salinity,
Iarvae metamorphosed in 19 days.
As metamorphosis approaches, Iarvae should be
inspected daily (Jones et al, 1993). Indications of the onset of metamorphosis include a
shelI iength of the above mentioned range, a golden brown shell colour, and foot activity
(Chew et al, 1987). An additional indication is an alteration between swimming and
crawling lifestyles (Jones et ai, 1993). This transitional stage may be extended for up to
two weeks if water temperatures are sufficiently low (Robinson and Breese, 1984).
Metamorphosis is characterised by the loss of the velum and the animal's complete
dependence on its foot for mobility. Upon settlernent, attachment to the substrate is
achieved via a byssal thread. Should the substrate prove to be less than ideal, the byssal
attachrnent may be severed and a new location chosen (Chew et al, 1987).
Several factors affect the success of larvai setting, including: larval density, temperature,
bacterial loading, fouting, dgal btooms, and feeding (Robinson and Breese, 1984). A
lavai density of between 150 to 200 mimais pet- square centimeter shouId be used for a
duwnweIler settlement tank. Temperature should be similar (or slightly lower) than the
lama1 rearing tanks (Chew et al, 1987; Utting, 1993). As previously rnentioned, if
temperatures become too high, problerns with bacterid and algal growth may occur.
Clams at this stage appear to be mosc sensitive to high numbers of bacteria within the
system, especially Vibrio spp., which =y
cause high or complete mortaiity (Elston,
1984; Elston, 1990). Most bacteria in smalI numbers are hannless, and reflect n a t u d y
occurring nurnbers.
Fouling of the pediveligers' shells rnay become a problem as
increased diatom numbers result with the progression of the season (Chew et al, 1987). A
light spray with salt water should remove the fouiing organisms. Algd blooms either
within the system or environment may have an adverse effect on setting, by either
slowing d o m setting, or fouling the velum and resuiting in increased mortality (Jones et
aI, 1993). The addition of food is still necessary to ensure the setting pediveligers achieve
sufficient nutrition for metamorphosis to be carried out.
Severai methods exist for setting larval clams, these include water tables, downwellers,
setting screens, floating kaches, and oyster setting tanks (Jones et al, 1993). Water
tables are shaiiow sided tanks offering a high surface area to volume ratio to
accommodate the pediveliger's characteristic lifestyle of swimming and crawling- The
system may either be a flow through or static system. Static systems still however require
a water change of twice daily or more. Water tables offer the advantage that they may be
stacked, thus consewing space (Jones et ai, 1993). Downweîiers consist of screened units
holding larvae with water passing d o m over the larvae and out though a second screen at
the bottom, Larvae are added to the screened units (screen size 120 pm) at a density of
150 to 200 per sq.cm, with a flow rate of I litre/min./rnillion pediveligers (Chew et al,
1987). Setting screens are essentially a modification of downweller designs, in that they
consist of a shailow-iipped tray with a screen bottom (120 pm in size) that are ffoated in
larger tanks (Jones et al, 1993). Density of animals and flow rate are the s m e as used for
downwellers.
Two "low technology" alternatives are available for setting larvae. Floatinp beaches
allow setting in locations where electricity for pumping is unavailable. nie structure
consists of a wooden €rame with removable screens at either end. The structure is filled
with approxïmately 5 cm of sand and anchored in a well protected, well flushed area
Pediveliger clams are added at a density of 1.5 rnilliodsq. m of sand. Being a system that
is not easily monitored, set success is be mcuIt
to determine. This system appears to
offer better success as a field nursery, rather than as a setting meîhod (Jones et al, 1993).
Oyster settïng tanks offer aaother alternative for "low technology" setting of clams. A
thin layer of silica sand (2 cm) is spcead over the bottom of the tank, and larvae are added
at a density of 150/sq. cm. Water should be changed twice per week, and dg- added at a
rate of 20,000 to 50.000 cells/rnl (Jones et al, 1993).
The use of substrate in larval rearing tanks presents the same dilemma as it did in
broodstock conditioning tanks. Jones et al (1993) found no difference in set success
between ground shell (200 p),
sand (200 p)and no substrate. A difference in
handling, maintenance, and estimating set success were noted. The use of a substrate
increased the available surface area for setting, and helped preveot the clogging of screens
in downwellers. The disadvantage of using a substrate was that set success (or failure)
could not be detennined until the animals were larger and more easily screened.
Screening becarne a more complex process as the clams were attached to the substrate via
byssd threads. On the whole, production was made easier, however, monitoring was
harder.
In naturd populations, the presence of adult clams has k e n shown to influence the
settiement of spat (Williams, 1980). A negative correlation was obsemed between the
number of newIy settled spat and the density of aduIt clams. It has been suggested that
spat are inhaled by adults dunng feeding, mpped in mucus, and discharged as
pseudofeces. Successful survival to adulthood may iherefore be dependant on the ability
of the farvae to detect and avoid adults.
Setting clams should be fed a diet of higb quality Iive algae, dned dg=, or algal paste
(Chew et al, 1987; Curatolo, 1993; Jones et al, 1993; Utting, 1993; Coutteau et al, 1994a;
Coutteau et al, 1994b). The amount of naturally occurring algae wiIl Vary with the site,
therefore it is often necessary to supplernent the incoming water with an algal
supplement. The most mutinely used p i e s are: C.gracilis, .'2 pseudumna (3H clone),
T. isuchrysis, 1. galbana, C. meuileri, C. calciirm, Al oculara, and Skeletonema spp
(Langton et al, 1977; Laing f 993; Utting, 1993; Coutteau et al, 1994a). A mixture of
severai species of algae (cornbining both diatoms and flageliates) results in a more
cornplete diet (Langton et al., 1977; Coutteau et al, 1994a). Supplemental feeding rates
depend on the availability of natural algae within the system.
Most commercial
hatcheries feed juvenile clams a mixture of algal species at a rate of 4% dry weight dgae
per live weight of clam per day (Chewet al, 1987; Utting, 1993). The preferred manner
of feeding is twice daily: once in the morning, and the second 7-9 hours later (Laing et al,
1990; Coutteau et aI, 1994a). This feeding regime results in increased utilisation of the
algal food, and improved growth. Feeding should be adjusted to accommodate a rate of
between 20,000 to 50,000 ceIls/ ml of water in a static system, and 10,000 cells/ml
flowing water in a flow throue system (Jones et al, 1993). If a flow through system is
used, heat and algae can be recovered through the use of a heat exchanger and by using
the outflow water to grow smaller seed. The flow rate for a flow through system should
be adjusted such th& approxirnately two complete water changes per day occur (Chew et
al, 1987). In a static water system, the water is changed twice per day as two separate and
complete water changes. In both systems the sme volume of water per larva is required.
3.1.6 Alternative Feed Sources
In recent years, research has been directed toward low cost alternative feed sources for
juvenile molluscs (Laing et al, 1990; Curatolo et al, 1993; Laing, 1993; Coutteau et al,
1994a; Coutteau et al, 1994b; Sauriau and Baud, 1994). The intensive production of Iive
algae for bivalve rearing requires space, energy and skiIled labour. As a result, the cost of
canying out these activities can comprise as much as 30% of the total operating cost of
the hatchery (Adams et al, 1991). The estimated cost of algal production (in 1994 US$,
not indexed for inflation) ranges from $50 to S400 per kg dry biomass (Coutteau et al,
1994b). Various alternatives to the use of üve algal diets have been exploreci, including
such avenues as the addition of baker's yeast (Saccharomyces cerevisiae) (Coutteau et al,
1994b), the use of spray-dried algal die& (either dong or in combination with live diets)
(Laing et al, 1990; Curatolo et al, 1993; Coutteau et al, 1994a), and the artificial breakage
of diatom filaments for increased assimilation (Sauriau and Baud, 1994). The use of
baker's yeast as a food substitute for Mercenaria mercenaria, as exexamined by Coutteau et
al (1994b), found that replacing 50% of the algal ration with yeast did not result in a
significant decrease in growth rates relative to clams fed algal diets. The substitution of
80% of the algal diet with yeast led to growth rates reaching 90% of the algd fed
controls. The physical breakage of long chained diatoms (Skeletonema costatum) into
segments less tha. 60 pm has k e n investigated by Sauriau and Baud (1994). The
researchers suggest implications for mollusc culture in several area, including:
1)
reduction in sinking rate due to a decreased size distribution; 2) a decrease in the
production of pseudofeces due to the elimination of filaments Imger than 60 pl;3) an
increased potential for nutrient assimilation resulting from weakened ce11 walls and; 4)
the addition of organic materiais to the water (both particdate and dissolved) from
damaged cells.
The use of spray-dried algal has recently been receiving much attention (Laing, et al,
1990; Curatolo et al, 1993; Utting, 1993). In an atternpt to provide cost-effective
alternatives for algd production andor insurance against algal collapse, artificial and
replacement diets are king examined. Dried algal diets are advantageous in that they are
of a known, defined, biochemical composition (Laing et al, 1990). Despite attention to
this area, problems stiii exist. To be an acceptable artXicial diet, the diet in question must
remain in suspension, be non-toxic, and be easily assimilated and digested (Laing et al,
1990). In trials conducted by Curatolo et al (1993) it was show that juvenile diets of
100% dried algae, and supplements up to a%,
did not produce satisfactory growth. It is
thought this may be due to bacterial contamination from decomposition and decay of the
dried dgae. Diets that were composed of 80% Live/20% dry and 60% live/40% dry
resulted in good growth performance. A suggested feeding regirne (Curatolo et al, 1993)
for juvenile Manila clams (2 - 3 mm) is to commence initial feeding on either a totally
live diet or 80% live/20% dry. After a month, this c m be replaced by a diet of 60%
live/40% dry. It has also been suggested (Laing et al, 1990) that the drying process may
facilitate the digestability and physical breakdown in the gut of the larvae, thus leading to
more efficient assimilation and utilisation. It is thou@ the physical conditions applied in
the drying process affects the integrity of the ce11 w d .
Adaptations to nutritive stress in juveniles have been examined (Laing, 1993), as bivalve
molluscs are adapted to withstand relatively long periods of nutritive stress as a result of
living in coastal environments in which food supplies Vary seasonally. The degree of
response to nutritive smss is linked to biochernical reserves within the animal (Laing,
1993). Carbohydraîes are used preferentially over Iipids and proteins as an energy source.
This preferential use over Iipids and proteins may be a means of protecting against the
loss of structural components. Therefore, those juveniles with higher carbohydrate
reserve levels adapted more successfully to nutritive stress. Based on these findings, and
the findings of Laing and Lopez-Alvarado (1994) that spray dried diets resulted in a
higher carbohydrate reserve, p s t nursery size clams should be fed a diet composed
partially of spray dried algae to increase their carbohydrate reserves. An increase in
carbohydrate reserves will dlow the newly planted clams to ùe better adapted to
fluctuating food leveis.
3.1.7 C u b g
During juvenile gowth a common practice is to cul1 at regular intervals and discard the
smaller animals. The logic behind culling in the hatchery and nursery is that slower
growing individuals in this environment will be the slower growing individuds during the
grow-out stage, and hence a longer period of time until a retum on capital is seen. Such
an assumption rnay not however be as logicaliy sound as it may seem. In work conducted
by Hadley (1993) it was shown that clams which perforrned well in a hatchery
environment did not necessarily perform well in the nursery or grow-out systerns. By
culling in a hatchery situation, one is selecting for individuals which grow well under
constant and optimal conditions - not those conditions which are found in the grow-out
environment (and to a lesser extent in the nursery environment).
In a hatchery
environment, temperature, salinity, food arnount and quality are al1 constant and present
at optimal levels to ensure maximum growth. In the more variable environment of a
grow-out systern the previously mentioned factors fluctuate to a much greater degree.
Thus, by culling in the hatchery, individuals with rapid growth in a constant environment
are selected for, and these individuals may not necessarily perform well in the highly
variable gow-out environment. It is therefore advantageous to maintain a high d e m e of
menetic variability within the population. In order to realize any genetic improvement in
O
the deveiopment of broodstock, selection for desired traits must be carried out at the
appropriate time (Le. selection for rapidly growing clams should be made at the end of
year 3, not during the hatchery or nursery stage).
3.1.8 AIgal Culture Methods
AlgaI culture is one of the most crucial components of a hatchery system, as early
juvenile stages are the Iargest consumers of intensively cultured micro-algae (Coutteau et
al, 1994a). For hatchery purposes, two important criteria must be met: 1) the food supply
must be continuous and 2) appropriate to the l a m e (Wohlgeschaffan et al, 1992). Being
such a large cornpoueut of the hatchery operation, the cost of algal culture c m approach
upwards of 30% of the total operating costs of the hatchery. Due to the high proportion
of operating costs brought about by aigai culture, it is not surprishg that much effort has
been conducted in the area of algal research. M a t foiiows is a brief overview of aigal
culture techniques as used in bivalve hatcheries.
Sterile algaI cultures are used as starter cultures within the hatchery. These cultures c m
be obtained from research facilities, algae laboratories, or another hatcheries' parent stock
(Hurley et aI, 1987). Regardless of its origin, the culture must be a monospecific stock in
. a sterile medium, and is to be used by the hatchery to produce large volumes of clean,
fast-growing, and good quality food. The usuai rnethod of production starts with the pure
cuIture king used to inoculate 500 ml flasks containing cultue medium (stock cultures).
The culture stocks are perpetuated by transfemng thern to new 500 ml flasks, or used to
inoculate 2000 mi flasks. Up to this point, dl culturing of algae occurs in an area of the
hatchery designated exclusively for aigal production (in an attempt to maintain a stenle
rearing environment) (Hurley et al, 1987). Following growth in the 2000 ml fiasks, larger
tanks (ranging in size from 90 to 5000 1, depending on the method of culture king used)
are inoculated with the product from the 2000 ml flasks (Chew et al, 1987; Jones et al,
1993). After 3 weeks from the start of initial algal production, harvest h m the Iarger
tanks takes place with a resulting density of approximately 10 - 20 million cells per ml
(HurIey et al, 1987).
There are three general methods in which hatcheries are able to produce a consistent
supply of appropriate food organisms (Claus, 1981; De Pauw, 1981): 1) cultivation of
phytoplankton in open outdoor ponds, 2) cultivation under controlled (or enclosed)
conditions either indoors or outdoors, and 3) bloom induction in natural seawater through
the addition of fertiiizers or sewage effluent. The major problems associated with the
fmt and last methods are the lack of control over the species being cultured and water
quality concems (DePauw, 1981). Within these three methods of algal production, two
broad categories exist: batch culture and continuoudsemicontinuousculture.
Batch culture involves the propagation of a senes of progressively Iarger culture vessels,
with the final vesse1 containing a large volume of enriched sea water. These are
illuminated for a period of time and the entire crop is harvested at the mid-log or
stationary phase of growth (DePauw, 1981). A more recent shift in commercial algal
production has been toward the use of continuoudsemi-continuous culture methods
(Richmond, 1987). This mode of production involves constant removal of a ce11
suspension from the culture vesse1 with the addition of an equal volume of growth
medium. Harvesting begins when the culture reaches a mid to late Iog growth phase.
The continuous dilution rate keeps the algal density at an optimum level for maximum
yieId. This mode of culture offers the advantage of maintainhg culture production near
its maximum leveI while using a minimum number of culture vessels. It also offers the
further advantage of k i n g able to be automated to a greater extent, and as such, labour
costs rnay be reduced. Two methods of semi-continuous culture are in use on the west
Coast of Canada: open culture (open tanks) and closed (bag culture) (Jones et al, 1993).
in each case, the production level and length of time varies with species and production
method.
As previously mentioned, algal production can occur in two types of vessels: open ponds
and enclosed vessels. Open ponds provide a means of achieving a large surface area to
volume ratio, and can encompass areas up to 5 0 m2 (Tredici and Materassi, 1992).
This large space necessitates they be located outdoors and rely on arnbient light.
Common designs include circular or rectangular ponds with paddlewheels (Richmond,
1987). The culture may be started either by inducing a natural bloom, or by following a
series of subcultures before inoculation. A major disadvantage of open ponds over other
systerns is the lack of control over the entire culture system (Witt et al, 1981). Being an
open system entails problems with nutrient limitation, contamination with undesirable
species, or predation by protozoans, rotifers or crustaceans. A mass development of
grazers within the algal culture systern can destroy it within a matter of days. Open ponds
have lower algal yields as a result of non-optimal temperatures, production loss due to
dark respiration at night, and a non-optimal Iight regime (Witt et al, 1981; Tredici and
Materassi, 1992).
Enclosed vesse1 production systerns include three types: horizontal tubukir systems,
vertical tubular systems, and panel systems (Richmond, 1987). Enclosed systems are
aimed at maximhing high cell density yields, and focus on such features as maximized
surface area to volume, efficient usage of light sources, and a more efficient mass transfer
of algal products (Tredici and Materassi, 1992). As the name implies, horizontal tubular
systems are composed of glas or Plexiglas tubes laid out horïzontally on the gmund. A
headerfgas separator tank is located at the head of the system, where nutrient addition and
gas exchmge occur. Vertical tubular systems solve the problem of space requirements
imposed by horizontal systems (Tredici and Materassi, 1992). The system generally
consists of a series of tubes/columns otiented vertically, with inlet and outlet ports for gas
and nutrient addition. Panel systems offer the advantage of maximized surface area to
volume, while at the saine cime allowing the producer to take advantage of naturd light
sources through a flexible axis of orientation (Richmond. 1987; Tredici and Materassi,
1992).
Environmental conditions play a critical role in the production of algae, as optimal
production can only be achieved under very strict environmental parameters. One of the
most important parameters is iighting. Light sources may consist of fluorescent tubes,
metal Halide lights, natural sunlight, or more recently, the use of immersion core
illumination fias been developed (Hadley et al, 1987; Wohlgeschaffen et al, 1992; Jones
et al, 1993). In more northem latitudes natural light must be supplemented with artificiai
light (Hurley et al, 1987). Care must be taken when using natural sunlight to avoid direct
sunlight. Other parameters of importance are temperature and pH (DePauw, 1981).
Temperature fluctuations can cause tremendous variation in production levels, with levels
of greatest production being achieved in late spring, and lowest IeveIs of productions in
mid-winter.
If temperatures drop below SOC growth ceases all together, whereas
temperatures above W C approach the lethal limit of the algal species (Hurley et al,
1987). The pH within algal culture systems should be maintained between 7.2 to 8.2
(Jones et al, 1993). As the culture grows, the pH of the system will steadily increase, and
problems may develop if the pH exceeds 8.5. Problems usually occur in the fonn of
slowed growth rate or an algal crash. The pH of the system may be maintained through
the injection of CO2 at a rate of 4% with the air supply (Hurley et al, 1987). If natural
light is being used (and a resulting resting period occurs during the dark period),
supplementai CO2 addition may only be necessary dut-ing the fastest growth periods of
late spring and early summer (DePauw, 1981).
3.2 Nursery Culture
The nursery rearkg of bivalve molluscs is the intermediate step between the controlled
production of Iarvae in the hatchery and grow-out in the wild. The nursery phase of an
operation represents a critical link in the clam grow-out process (Manzi and Castagna,
1989b). Placing the seed directly in a grow-out situation results in unacceptably high
mortality, whereas rearing the seed in the hatchery to sizes large enough to withstand the
stresses of the grow-out environment does not prove to be cost effective (Adams et al,
1993). In recent years this phase of mollur culture has been receiving more attention,
with the aim of raising post-set juveniles fmm a few millimetres to 1
- 1.5 cm, in a
minimum amount of t h e , at densities as high as possible, and at minimal cost and risk
(Claus, 1981). The conditions in the nursery are less sophisticated than in the hatchery,
therefore, seed can be held for longer periods of time and at lower cost untii sold to the
grow-out operator (Adams et al, 1993). Furthemore, the nursery enables a gradua1
transition from the hatchery to the grow-out stage, and therefore ensures increased
survivorship (Manzi and Castagna, 1989b). SeveraI nursery methods exist for bivalve
molluscs: intertidal racks arranged on the sea shore; trays suspended near the surface
from rafts moored in open water; trays suspended in mid-water on long lines without
costly floating structures; land based upweliing or downwelling systems; and land based
raceways (Claus, 1981; Bayes, 1981; Le Borgne, 1981; Spencer and Hepper, 1981;
Williams, 1981; Adams et al, 1993; Jones et al, 1993). A surnmary of various nursery
culture systems is presented in Table 6.
Table 6. Critical factors associated with various nursery systerns (Adams et ai, 1993).
Critical Factors
Raceways
w
Location
land-based
Maintenance
high
high
Capital cost
low
Replacement cost
Energy requifements high
Survival rates
high
SY-
Type
Upflows
Cageflrays
land-based field-based
high
rnoderate to high
low
high
high
moderate to high
low
high
high
low to moderate
A recirculating downweller involves the re-use of water within land-based tanks (Manzi
and Castagna, 1989b). Water is lifted fiom the holding tank and passed down through a
screen supporting the juveniks, thereby creating a recirculating downwelling current.
Food is added to the system and the water must be changed on a regular basis. This
system is limited by its size and is ody economically feasible for very small clams (< 500
pm)as food and tank requirements prove to be too great a cost for larger clams (Adams et
ai, 1993).
Another land-based nursery system comrnonly used in bivalve culture is an upwelling
system (Manzi and Castagna, 1989b). in this system, inflowing water enters the outside
of a screened unit containing the juvenile clams, passes up through the clams, suspending
them, and exits through the outfiow situated within the seed containing unit. This system
is effective for al1 sizes of clams, however, pumping costs for larger seed may prove to be
prohibitive (Bayes, 1981; Manzi et al, L984; Adams et al, 1993). A low cost adaptation
of the upwelling principle is the "coke" bottle system as described by Jones et al (1993).
In this system, plastic "coke" bottles are inverteci using the bottleneck as the water inflow
point. A marble is placed as a check valve in the neck, and a plastic tube near the bottom
(top when inverted) acts as the outflow. Juvenile clams are placed in the bottle, and the
flow is adjusted to fluidize the clams. The water flow is adjusted such that the clams are
suspended in the water column above the marble, but not so much as to keep individuals'
tumbling or constantly moving within the water column. One problem associated with
this system is uneven growth (Jones et al, 1993). This is the result of juveniles creating a
large unified m a s through the attachment of byssal threads, which tends to create
channels through which water and nutrients flow. As a result, those individuals closest to
the channels receive more food and hence expenence increased growth rates.
This
problem is characteristic of most upwellers, however, is more frequent in the coke bottie
system due to decreased handling and the funnel shape of the upweller neck.
Land-based raceways typicaliy utilize long, shallow, wooden trays which have been
covered by a protective coating of epoxy, resin, or lined with plastic (Manzi and
Castagna, 1989b). The raceway system may contain several layers of trays. A thin layer
of sand covers the bottom of each tray, over which the clam seed is distributed. Raw
seawater is pumped into one end to estabiish a horizontal flow across the seed clams
(Adams et al, 1993). A major disadvantage of raceway systems is that those clams
nearest the infîow (maximum effective flow) grow significantIy faster than those near the
outflow (minimum effective flow) (Hadley and Manzi, 1984). The use of raceways for
nursery culture in the Manila clam industry is not as prominent as it is for east coast
Mercenaria production.
An alternative to land-based upwelling systems, which have recently been gaining
popuIarity, are floating upwellers. These systems depend on tidal or mechanical methods
to force water through a seed mass within containers attached to a floating structure
(Spencer and Hepper, 1981; Williams, 1981). The most commonly used system is a
floating upweller systern (FLUPSY),which supports a series of individuai containers
dong a centrally enclosed channel. Water is forced out of the channel by either a
propellet or a paddtewheel, and is replaced by the upwelling flow of water from the
screened seed container%. The flositing system requires a protected site with warmer
temperatures and productive water. Heavy algal blooms are undesirable as they wiit clog
the system's screens and restrict water flow to the animais (Jones et ai, 1993).
Cages and trays present a "low-technology" alternative to the capital intensive on-shore
upweller/downweUer units or field-based FLUPSY units (Manzi and Castagna, 1989b).
Pearl nets (mesh size 1.5 mm) have the bottom surface area covered with a single layer
of seed. The nets are generaUy tied together to fom a single line, weighted at the bottom,
and hung from a long line (Jones et al, 1993). Oyster trays may be Iined with nylon
window screening, or alternatively have bags manufactured from window screening
placed inside, filled with a single layer of clam seed, and hung in the same manner as the
pearl nets. In protected areas with good phytoplankton supply, Japanese onion bags rnay
be filled with approxirnately 100,000 clams and hung from a long line or raft. This
method has resulted in high survival and good growth during the summer months
(personal observation).
Beach nurseries can aIso be used as an intermediate step before the final grow-out phase.
These areas generaliy have a substrate of pea gravel, are relativdy flat, and are located at
rnid-tidal height (Manzi and Castagna, 1989b). Seed clams are planted at densities as
high as 2500
- 3500 per square meter in an area cleaned of larger clams (Jones et al,
1993). Small mesh netting is then placed over the nursery area The clams are Iater
removed at a larger size for planting to other beach locations.
3.3 Grow-Out
Grow-out involves the cuIture of nursery pmduced seed on the beach until harvest size is
achieved. On the West coast of North Amerka two methods are commonly used: direct
seeding to the beach, and bag culture (Anon. 199ûa). Direct seeding to the beach, the
most common of the two, involves seeding clams (minimum 6 - 8 mm) directly to tidal
flats. The substrate should consist of a fairly soi3 mixture of gravel, cmshed shell and
mud (Anderson et ai, 1982). Clms are seeded at a density of 200 individuals per square
meter. Predator exclusion netting is placed over the seeded areas. The use of predator
exclusion netting has been shown to greatIy increase the survival of clams beneath the
nets (Anderson et al, 1982; Anon., 1990b; Spencer et al, 1992). In addition to increased
survival, predator netting has also resulted in increased growth rates. This is thought to
be caused by predator netting disrupting current flow, and creating little eddies, thereby
concentrating algae for feeding adult clams. In a snidy by Spencer et al (1992) it was
found that thin flexible nets offered a survival rate of over 90% when raised off the
substrate by 50mm. in commercial practice, this could be achieved by supporting the net
either at the edges or in the xniddle using plastic floatation devices. The additional cost of
raising the netting is projected to be 25% extra of the original. After three to four years of
growth, the ciarns are harvested. Mortalities of 50% can be expected if clams are seeded
out at the 6 - 8 mm size. If clams are grown to a larger size (8-10 mm) in the nursery,
survival rates can be expected to increase to close to 75% (Chew, 1989). Maintenance
during the grow-out period consists mainly of keeping the nets free of fouling organisms,
repairing damaged nets, and preventing poaching.
In the state of Washington, substrate enhancement is one option allowed to lease holders
in an attempt to increase the area avaiIabie for clam culture (Anon., 1990a; Thompson,
1990). Gravel and crushed shell are added several times in 2 cm layers to turn mud flats
into suitable clam culture m a s . The addition of al1 the gravel at once is not practised so
as to avoid smothenng the naturally occumng organisms. The srnothered organisrns
would eventually decompose, creating anaerobic conditions and the release of hydrogen
sulphide gas, thereby creating a potentidly toxic environment for Manila clams. The size
and type of grave1 added is criticai for mrning non productive beaches into clam
producing beaches. The most success has been observed with smail pea gravel, ranging
in diameter from 0.6 - 1.9 cm. This size of gravel is thought to provide the right amount
of interstitial space necessary to collect the finer sediments required by clams. Angular
gravel was found to compact too easily, thereby eliminating the interstitial space
(Thompson, 1990). Thom et al (1994) have shown that graveling beaches increases the
bivalve density to at l e s t twice that of ungraveled controls.
The grow-out of clams in bags is also practised to a certain degree on the
West Coast
of
North Amenca (Anon., 1990a). Bags are typically 30 cm by 90 cm and made from 6 mm
vexar. The bags are seeded with appronimately 500, 10 - 12 mm clams and stapled to the
beach at the 1 m tide level using rebar staples.
The beach is excavated severai
centirneters to provide a secure setting for the bags, and to allow the bags to fdt with
sediment. Clam survival is approximately 70 - 80% at harvest (Anon., 1990a). This
rnethod is more capital and labour intensive, and as a result, is much less popular in
British Columbia thaa direct beach seeding with predator exclusion netting.
4.0 The Operating Environment
4.1 The Market
Presently, of the areas licensed for foreshore aquaculture in British Columbia, just over
400 ha are designated for Manila clam culture (B. Kingzett, BC Shellfish Growers
Association, personal communication). Of these 400 ha, approximately 200 ha are either
non-productive ground, or else designated as oyster ground. Of the remaining 200 ha
avaiiable for clam culture, less than 100 ha are actively k i n g farxned. The Manila clam
industry is undergoing a fairly rapid expansion, and since 1994 production of Manila
dams has increased by over 60% (Anon. 1996a). The area designated for clam culture is
projected to double by 2005, and according to the federal govemment's Aquaculture
Developrnent Strategy, production levels are forecasted to rise as high as 7,500 MT by the
turn of the century (Anon. 1995). These high levels of production should be regarded
with a degree of caution as they assume al1 200 ha of proposed culture area will be
producing dams at a density of 2 0 ~ l r d . Despite what may seem to be a somewhat
unrealistically high production goal, the industry is still undergoing an expansion
nonetheless. As a result, an increased demand for Manila clam seed will be evident. The
current demand for Manila clam seed can be estimated by assuming an average seeding
rate of 125 clams/m2 over 100 ha. This results in a current demand of 125,000,000
clams. Should the current area designated for clam culture corne under full production
within the next 4 to 5 years, the demand for clam seed would double. If by 2005 the area
has doubled to 400 ha, a demand for half a billion seed clams a year would exist.
4.2 Target Market
The target market for the proposed hatchery will consist of the 37 producers who are
cumently identified (BC Shelifish Growers Association, personal communication) as d a m
producers, as well as other clam producers who may enter the market with the projected
industry expansion. A locaily situated hatchery would have the advantage of being able
CO
offer seed clams already conditioned to the local grow-out environment.
This
distinction should be a key selling point in the cornpanyysattempts to attract customers.
Once established, the company rnay wish to expand its sales to outside the country, in
particular, Washington and Oregon. In ail Iikelihood, this would prove a difficult market
to penetrare, as established hatcheries are aiready present in these areas. The companyys
selling philosophy of producing seed for Locd conditions would aIso work against it.
Perhaps the only advantage that the company rnay possess wouId be a price differential
brought about by a weak exchange rate.
4 3 Cornpetitors
Several diréct cornpetitors exist for the company. In British Columbia, there are two
companies on Vancouver Island that are capable of supplying growers with clam seed.
However, most of the seed is imported from California (B. Kingzett, personal
communication). The two locally situated hatcheries do not produce on a large scale, but
rnay possess a competitive advantage in that they know the curent market situation and
rnay be capable of expanding operations quickly to keep pace with the expanding market
place.
They could also claim the same selling philosophy adopted by the proposed
Company (i.e. selling seed for local conditions). The California based hatchery does not
possess the advantage of being able to supply seed conditioned for local grow-out
environments. It rnay also suffer during times-of weak exchange rates. As a result of
being the largest supplier, the Californian based hatchery may have established
cornfortable supplier-customer relationships that rnay prove dificult to break.
4.4 Key Assets and Skills
In order to be a successful commercial enterprise, the hatchery must concentrate in the
liey areas of marketing and producing. In the marketing sector, major factors tha~must be
developed include (Kolter and Turner, 1993):
The development of an effective distribution systern.
Building a reputation for producing a quality product, available when requested.
Building relationships with local producers in an attempt to attract new customers.
Suppling customers with a choice of different size classes of seed.
In the production sector, the Company should concentrate on:
Expenence and expertise in al1 aspects of hatchery and nursery production.
Experience and expertise in aspects of mass aigal culture.
Development of contacts in the shellfish industry and aquaculture supply industry.
The strengthening of these key assets and skills will ensure that the Company becornes a
profitable enterprise in the shortest possible time.
5.0 Proposeci Project
At this point it is necessary to examine the project in a bit more detail and discuss some
of the design parameters of the facility.
5.1 System Design
The proposed project is based upon design assumptions and criteria laid forth by Hurley
et al (1987), Adams et ai (1991), and Adams and Pomeroy (1992) in their analyses of
bivalve hatchery systems. Their design criteria have k e n modified to meet the needs of a
Manila clam hatchery sitxated on Vancouver Island, BC.
5.1.1 Permanent Structures
The building housing the hatchery and on-land nursery will be located on a 50 rn lengeh
of shoreline property, with the necessacy dock and pumping infrastructure supplying the
hatchery with its water needs. The basic component of the design includes a building
housing the shellfish production area, a greenhouse, a stock culture room, a mechanical
room, and a srnall office. While the construction of the building is f&irly basic (either a
wood frame or steel arch type building), a sophisticated foundation capable of
withstanding the weight of the rearing tanks must be in place (Hurley et al, 1987). The
greenhouse portion of the building must have access to suniight year-round, and face
within 15' either side of true south. Aside from the hatchery building, an outdoor nursery
of upwellers rnust ais0 be constructed. The upwellers will be placed on a concrete pad of
similar design to the building foundation. A sea water transmission system consisting of
two 30 hp purnps, associated fittings, dock and pumphouse wiIl have to be constructed
(Adams et ai, 1991).
5.1.2 Fïoor Plan
The sheIlfish process area will be the largest area in the hatchery housing the four 40,000
L iarval rearing containers. Overhead lines of saltwater and air will feed the various
tanks. The drains from the larvai rearing tanks will drain into a main drain set in a floor
strip drain. Spawning tables and broodstock containers wilI also be housed in this area.
The stock culture room is the area used to prepare algal cultures for the greenhouse. The
main equipment will consist of flasks and carboys, a transfer chamber with an ultraviolet
light, and illuminated shelves. The stock culture room will be located directiy adjoining
the greenhouse and in an attempt to limit contamination, will have limited access from
the rest of the hatchery (Hurley et al, 1987).
-
The greenhouse is to be used to fimher develop the dgal culture in mass culture. This
m a
wiIl house the KaIwaI tubes and batch culture tanks.
Due to the extreme
temperatures chat wilI be experienced in the greenhouse, a good ventilation system wiII
have to be instdIed. A Fan with a thermostat control~wiIlbe instailed to exhaust warm
air, while night insulation will cover the windows to prevent heat loss during the night.
5.2 Water Sources and Filtration
The water source to be used for the hatchery will be pumped from a bay meeting the
criteria laid out in Appendix B. Two 30 hp pumps will be necessary to pump the water to
the hatchery. A combination of a sand filter and bag filter (35pm)will be used to filter
out any suspended matter in the incoming water. Water to be used for aigal culture wilI
be purified using sodium hypochlorite (10 ppm) for several hours and dechlorinated using
sodium thiosulfate.
Water for conditioning adults and lasval rearing need not be
stedized The water wili however have to be heated using the heat pump. A backup
generator wilI also be in place in the event of a power outage.
5.3 Nursery
The nursery wiIl be divided into two production segments. The first will involve a
passive flow systern in the shellfish processing section of hatchery. This segment of the
nursery will rear the clams from pst-set to 1-2 mm. Upon reaching 1-2 mm, the seed
will be transferred to the second segment of the nursery. This segment will consist of a
forced flow upweihg system (360 upwelIers in total) located outdoors on a concrete pad
covered with a steel comgated roof. Seed will be reared in these upwellers until they
reach marketabIe size (usuaily 6-8 mm).
6.0 Financial Analysis
This section will examine the financial feasibility of the proposed hatchery. The previous
sections have dedt with the technical aspects of Manila clam husbandry, and have shown
that such an undertaking is technicaily possible. This section will examine the financiid
considerations of the project and determine whether it is financiaily justifiable.
6.1 Estimate of Capital Expenditures
A detailed iist of the initial capital investment and subsequent investment expenditures
over 10 years is given in Table 7. The land allocated for the project is 50 rn of shoreline
property. It should be noted that the cost of a vehicle is not included in the capital
expenditures, as this is to be leased The initia1 capital investrnent for the proposed
venture is $537,880, of which $447,122 (65%) is to be borrowed fiom a bank or other
financial institution, with the remaining $240,758 to be supplied by owners or investors.
Table 8 lists the annual depreciation of capital assets. For income statement purposes,
depreciation is assumed to be straight-line, with a salvage value of $0.
6.2 Financial and Biological Assumptions
In generating the 10 year pro-forma financial statements for the proposed project, a
number of assumptions were made. The assumptions made in this text are modifications
of those by Adams et al (1991), Adams et al, (1993), and Adams and van Blokland (1995)
for a Mercenaria hatchery and nursery system. These assumptions are:
O
Production volumes and revenues remain constant over the 10 year period
examined. By not subjecting revenues to infiation, a conservative price reduction is
worked into the company's financial projections.
I
I
*
..,
I
CI.
l
& '
C
4
O
N
'
I
.
I
0
I
.
.
8
I
.
7 - F
8
$
O
.-
.
f
r
in
88
-3
'
I
1
Z8
ln
1
1
1
1
8
I
I
I
I
I
I
I
*
Table 8. Annual depreciationschedule of capital assets
Assumes a straiqht-line depreaation schedule with a salvage value of $0
Years of
Use
Building
Air handlingsystem
cornpressad air
Support hb
Badc-up generator
Security system
DodJpump house
Saabvater system
PumP
PVC pipe 8'
vah,eS.iïîüngs. e b
Water treatment
Sand fntraüon
-
-
Wsystm
WcmfiHraIion (35 ptn)
Heat pump
Seausiter resemir
Fiings, Mc
M i s Equipment
Bruuâstock maintenance
Tanks
Water chiller
M i equ-pment
Laival culhire
Spamii tables
Lanral -MIS
k k c equipment
Algal culhim
Iroailationhood
-flasks
Caibay w e m
Kalwalbibes
Aïr pumpdaerators
w
u
g
i-
Autodave
Batch culhire tanks
MisceqrDpment
Merai h a i i i lïghts
Algae resenroin
Penstaloc pumps
Post-set maintenance
Domnnrallertanks
Oownweiien
Watet system:
motorslpumpsletc.
lDaures
Nursery
1. Passive ibw systern (pipes.
qiinders, standpipes,etcJ
2. Pad (100 sq. m)
(dfainags,water. electricity)
Comigated ml
3. Forced u p h system
(cycünder. seteenS. inflow)
4. Racksystm
5- Culüng sueens
6. Miscellaneow equipment
Office Equipment
TOTIL
Initial
Annuil
Invesbnent Dapraciation
Al1 loans (capital and operationai) are at 12% interest per annum.
Any short-faii in cash is covered by an operating Iom. This loan is to be supplied
based on the short-frùl projections in the cash flow schedule, and a Line of credit
estabIished by the Company.
4
Capital loans are for IO years and guaranteed by a government business
development program.
Lmd costs are caiculated at $4,00O/m of high grade water front property (Century
2 2 , Courtenay, BC, personal communication)
Initia1 start-up capital loans assume that 65% of the cost is finance& with the
remaining 35% coming fiom ownersrinvestors. Funds for replacement capital assets
are borrowed.
Capital assets are depreciated using straight-line methods. The salvage value of
capital assets is $0.
Retums are after taxes, A tax rate of 50% is used.
An annual infiation rate of 2% is incurred for ali operating expenses. Revenues are
heId constant.
The s e l h g price of seed is $8.00/1000. Ali seed are sold at the 6-8 mm size, and
shipped F.O.B.from the hatchery.
The discount rate for net present value (NPV)caiculations is 10%.
The Stream of values used for intemal rate of retum (IRR) and NPV calculations is
the annual "net cash flow" of the operation.
Survivorship of the larvae is 20%. Survivorship of the spat is 10%. The resuIting
overall survivorship from egg to 6-8 mm seed is 2%.
The average fecundity of femaies is 2.3 x 106 eggslfemale.
3.125 x 10 9 larvae are produced, resulting in the production of 6-25x 107 6-8mm
seed annuaily.
6 3 Pro-Forma Income Sbtement
The income staternent (Table 9) for the proposed project has b e n projected 10 years into
the hture. A hedthy net profit of 17% is redised at the end of the f i t and second years,
followin,o which it rises to 18% for the remainder of the projected period. Bearing in
mind that revenues are held constant and operating expenses are subjected to a 2%
inflation factor*the operation actuaily become more profitable as time progressess- At
the end of 10 yem, the accumulaîed profits of the operation are $893,673.
ui
constructing the income statement, a number of assumptions were made, these being:
Packing and selhg expenses are assumed to be 1% and 2% of revenues
respectively.
Site maintenance is allocated at 1% of building cost.
Vehicle maintenance and insurance is estimated to be $4,ûûû/year.
Property taxes are allocated at 1% of the original value of buildings and permanent
structures.
Salaries and wages are dlocated at $60,00O/year for two technicians and
$40,00O/year for one manager. Benefits and other labour related costs are added at
10%.
A contingency fund of 5%of annuai operathg expenses has been alloted for the
first 2 years.
A truck lease requiring an inital $1,000 payment, followed by $4ûû/month has been
taken out by the Company.
Al1 other costs are the same as those prescribed in the annual operating expense
summary (Table 10).
6.4 Pro-Forma Cash Flow Schedule
The 10 year pro-forma cash flow is given in Table 11. This scenario displays the
operation under fixed and ideai conditions. The assumptions made in sections 6.2 and 6.3
were used in the construction of the cash flow schedule. Table 11 also includes a
sumrnary of debt outstanding.
Table 9. 10 Year Pro-Forma lncome Statement
Year 1
Year 2
Year 3
Year 4
500,000 500,000 500,000 500,000
Year 5
500,000
500,000
Year 7
500,000
53,060
5,306
70,040
4,245
5,306
10,612
54,122
5,412
71,441
4,330
5,412
1 0,824
55,204
5,520
72,869
4,416
5,520
1 1,041
56,308
5,631
74,327
4,505
5,631
1 1,262
57,434
5,743
75,813
4,595
5,743
1 1,487
58,583
5,858
77,330
4,687
59,755
5,975
78,876
4,780
5,858
11,717
5,975
1 1,951
Total COGS
140,000 142,800 145,656 148,569
151,541
154,571
157,663
160,816
164,032
167,313
Gtoss Margin
360,000 357,200 354,344 351,431
348,459
345,429
342,337
339,184
335,960
332,687
4,800
3,184
46,294
46,478
46,693
1,061
3,651
4,245
2,547
6,367
6,367
O
4,800
3,247
39,681
46,478
47,627
1,082
3,724
4,330
2,598
6,495
6,495
4,800
3,312
33,067
46,478
48,580
1,104
3,798
4,416
2,650
6,624
6,624
O
4,800
3,378
31,028
46,478
49,551
1,126
3,874
4,505
2,703
6,757
6,757
O
4,800
3,446
23,906
46,478
50,542
1,149
3,951
4,595
2,757
6,892
6,892
O
4,800
3,515
16,784
46,478
51,553
1,172
4,031
4,687
7,030
7,030
O
4,800
3,585
$3,880
46,478
52,584
1,195
4,111
4,780
2,868
7,171
7,171
0
Total Expense
197,375 l9Ol897 176,847 171,687
166,556
161,454
1 60,957
155,408
149,891
148,623
Net Plofit before taxes
1 62,625 766,303 177,497 l79,744
l8lI9O4
183,975
l8lI88l
183,776
186,077
184,064
Revenues
Year 6
Year 8
Year 9
Year 10
~00,000 500,~Oo 500,000
Cost of Goods Sold:
Electricity
Lab Supplies
Technicians
Pump maintenance
Packing
Selling
50,000
5,000
66,000
4,000
5,000
10,000
51,000
5,lO0
67,320
4,080
5,100
10,200
52,020
5,202
68,666
4,162
5,202
10,404
Expnses:
Truck Lease
Insurance
Interest
Depreciation
Wages
Site maintenance
Property taxes
Vehlcle
HeatFuel oil
Miscellaneous
Supplies/expendables
Contingency Fund
5,800
3,000
66,135
46,478
44,000
1,000
3,440
4,000
2,400
6,000
6,000
9,123
4,800
3,060
59,521
46,478
44,880
1,020
3,509
4,080
2,448
6,120
6,120
8,862
4,800
3,121
52,908
46,478
45,778
1,040
3,579
4,162
2,497
6,242
6,242
O
O
2,812
Taxes (at 50%)
8l,3l3
83,151
88,749
89,872
90,952
91,987
90,690
91,888
93,038
92,032
Net Profit after taxes
81,313
83,151
88,749
89,872
90,952
91,987
90,690
91,888
93,038
92,032
616,714
708,602
801,641
893,673
Accumulated Profits/(Loss)
434,036
526,024
Table 10. Annual operating expenses
Production Costs
Electricity
Lab supplies Site maintenance
HeatiFuel oil
Truck fuel
maintenance
Pumplequipment maint.
Packing
Selling
Salaries and Wages
Manager
Technicians
Beneiiîs
Overhead Costs
Insurance
MisceIlanmus
Suppliedexpendables
TOTAL
Table 11. 10 Year Pro-Forma Cash Flow for lntegrated Halchery and Nursery
Beglnning Carh Balance
Caih Recelmi
From ~ p k t l o n s
Owneh lnvestrnent
Bank Loan
Totd Carh Inilowi
$
180,000
261,918
344,300
422,502
497,429
577,596
655,239
724,081
794,222
868,628
Caih Ouîfiow
Capital cosls
Variable wsts
Rwed cosls
Long.lsmi tkbt P a y m t
Principal
lnteresl
TOTAL DISBURSEMENTS
Opemting b a n
paymenl phcipal
Interest
-
Pm-tar Bank Balance
Incom Tarer (50%)
EndingCarh Baiance
$
180,000
261,918
344,300
422,502
497,429
577,596
655,239
724,081
794,222
868,628
936,814
Summaiy of debt outstanding
Long-term debt
Balance
$
551,122
496,010
440,898
385,785
330,673
275,561
258,564
199,217
139,869
115,667
52,415
Operating debt
Balance
Nurnber of Seed Sold
Price pet Clam ($)
62,500,000
0.008
An analysis of the cash flow shows a positive cash flow each year, with a resulting
closing bank balance in excess of 5900,000at the end of the 10 year period. Included in
the owner's investment and bank Ioans is an allocation of S 180,000 for working capital to
cover any cash short-fdls dunng the first year. During subsequent years, the cash balance
will be sufficient to cover al1 cash disbursements during the course of operations, while
waiting for revenues to be realised. In years 6 and 9, loans for $42,350 and $39,050 are
taken out to cover the cost of replacing capital assets.
6.5 Pro-Forma Balance Sheet
Table 12 presents a pro-forma balance sheet for 10 years into the future. From the
balance sheet a number of ratios can be calculated to determine the financial stability of
the operation. Foliowing the fmt year of operation, the current ratio is a healthy 4.8.
This is above the generaliy accepted benchmark of 2 (Anthony et al, 1995). As a result of
inventories k i n g completely sold off by the end of the fiscal period, inventory and
suppLies are valued at $0. This causes the acid-test (or quick ratio) to be the sarne as the
cunent ratio. The debt to equity ratio following year 1 is 148%. This value is somewhat
high, indicating that the Company is highly leveraged (Anthony et al. 1995). During
subsequent years of operation the debt to equity ratio is reduced as the Company pays
down its long-term debt, while at the sarne time increasing equity. Following the second
year of operation, the debt to equity ratio has dropped to 10595, and continues to fdl
throughout the course of operations.
6.6 Financial Sammary
Al1 of the financial projections are summarised in Table 13. At the end of the 10 year
projection, the project has accumulated $84,173 in net cash retums, after paying down its
long-term debt, and re-financing capital investments.
Table 12. 10 Year Pro-Forma Balance Sheet
Year 1
Year2
Year 3
Year 4
Year 5
Year 6
Year 7
Year 8
Year 9
Year 1O
794,222
868,628
936,814
O
O
O
794,222
868,628
936,814
2oo,QOo
100,240
62,215
382,455
200,000
94,nO
148,120
442,890
200,000
89,300
136,079
425,379
Asseta
Current Assets
Cash
InventorylSupplles
Total Current Assets
$ 261,918
$
$ 261,918
497,429
O
497,429
577,596
O
577,596
655,239
655,239
724,081
O
724,081
Flxed Assets
Land
Buildings (net ol deprec.)
Equipment (net of deprec.)
Total Fixed AmseIr
$ 200,000
$ 138,530
$ 286,859
200,000
122,120
182,076
504,196
200,000
116,650
135,855
452,505
200,000
111,180
112,077
423,257
200,000
105,710
102,086
407,796
Total Asrets
Liabiliîies
Current llabillties
Bank loan - cuvent rnaturily
3
Long-term llabilities
Bank loan
Total Llabilities
Owners' Equity
PaM-in-capital
Retalned Eamings
Toul Owner'r Equity
Total Llabilitiesand Equity
-
$ 625,389
O
Table 13. Financial Summary
Project
Year
Loan
Annuai
Net Sales Cash Operatlng
Expenses Repayment Depreclatlon
Revenue
Taxable
lncome
O
1
2
3
4
5
6
7
8
9
10
4
00
IRR
NPV
162,625
166,303
177,497
179,744
l8ll9O4
183,975
l8lI38l
183,776
186,077
184,064
Taxes Cash Flow lnvestment
(50%)
Eicpenditures
667,880
81,313
72,678
O
83,151
74,517
O
88,749
80,) 14
800
89,872
81,238
5,080
90,952
82,317
800
91,987
t 21,468
42,350
77,821
7,380
90,690
91,888
79,019
7,150
93,038
115,314
39,050
92,032
75,257
5,080
Net Cash
Flow
(667,880)
72,678
74,517
79,314
76,158
81,517
79,118
70,441
71,869
76,264
7O,l77
Cumulative
Net Cash
Flow
(667,080)
(595,202)
(520,685)
(441,371)
(365,214)
(263,696)
(204,578)
(134,138)
(62,269)
13,995
84,173
Based on the annuai net cash flow, the IRR and NPV are calculateci, resulting in 2% and
$1.13 1,492 respectively. These values indicate that the proposed facility is financially
viable. The payback period for the project is 8.8 yem.
6.7 Sensitivity Ariaiyses
The previous financial projections assumed that the facility is openting in a relatively
stable environment in which certain attributes that may have a profound effect on the
operation remain constant for 10 years. In light of this, the effects of changes in selling
price and levels of production on IRR and NPV were examined. Table 14 presents the
results of changes in selling price on the net cash flow of the operation. The selling price
was varied from the standard ($0.008) in 10% increments. Based on the net cash fiow
over a 10 year horizon, IRR and NPV were calculated for each change.
Table 14
indicates that the operation is very sensitive to price changes, especially downward
trends. Should the selling price decrease by IO%, the IRR decreases to -2%, making the
project unacceptable from an economic standpoint. Further 20% and 30% reductions in
selling price reduce the IRR values even more until they cannot be calculated due to al1
negative cash flows. The proposed venture is not as sensitive to upward pnce shifts. A
10% increase in price results in an increase to 8% in KR. In following a conservative
nature toward the project, one would be wise to assume that the selling price is more
likely to remain stable than increase.
Tabie 15 examines the effect of changes in levels of production on the financial stability
of the venture. The base level of production (6.25 x 107 seedlyear) was varied by
increments of 25%. A decrease in production levels of 25% (and any subsequent drops)
make a determination of IRR values impossible
f?~~?~~!sxd;~.,
AAhAhhhhhh
1
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b
Od)
OQCom-
-----
V)~~Ot~OCUOCUQ)VI
c u - < o ~ ~ ~ ~ = q c u , ~ u ? '. = ? .
5
Y Y Y Y
Such a sensitivity to decreased production levels cui be attributed to under utitisation of
capital assets. At decreased production levels, excess capital is tied up in idle capitd
assets. A similar trend is seen with an increase in production levels. As the production
Ievels are increased by 2595, an increase frorn 2% to 16% is observed with IRR values. It
should be noted that the same problem observed with under utilised capital assets in
decreased production levels will be observed with an increase in production, but with a
resulting over utilisation of capital assets. In the case of increases in production, the
hatchery cm only accommodate a certain level of increase before additionai capital assets
must be purchased. In al1 likelihood, an increase in production levels by 50% would
entail increased capital acquisitions.
6.7.1 Disaster Scenario
In the previous sensitivity analyses only one variable at a time was rnanipulated in order
to examine its effect on the net cash flow of the operation. However, in the r d world,
more than one variable at a time is exerting itseif on the operation. In an effort to
simulate this, a disaster scenario was examined in which a number of variables were
manipulated to produce a "worst case" scenario.
In this analysis, dong with the
assurnptions stated in sections 6.2 and 6.3, the following assumptions were also made:
A complete mortality of lame was arbitrarily assigned to year 5. This mortality
could be caused by any number of events, not the least of which could be disease or
Msmanagement.
The annual inflation rate was raised from 2% to 4%.
A "leaming curve" was associated with the fmt three years of production.
Assuming an inexpenenced management and staff, the cost of production for year one
was 30% higher than projected. Similar increases of 20% and 10% are observed in
years two and three. By year four, costs are at their projected levels, and only
subjected to inflational increases in subsequent years.
Table 16. Disaster Summary
Project
Year
Net Sales Cash Operating
Revenue
Expenses
toan
Annual
Repayment Depreclatlon
Taxable
lncome
Taxes
(50%)
57,674
92,253
136,088
155,676
(341,681)
128,932
1 14,599
99,700
84,211
68,109
28,837
46,127
68,044
77,838
O
1
2
3
4
500,000
500,000
500,000
500,000
5
6
7
8
9
10
IRR
NPV
500,000
500,000
500,000
500,000
500,000
178,486
119,919
55,112
55,112
311,949
241,991
160,814
11 0,446
122,723
63,252
--*
$211,495
00
ta
No value for IRR could be calculated due to al1 negatlve cash flows
64,466
57,300
49,850
42,105
34,054
Cash Flow
lnvestment
Expendltures
667,880
O
(81,411)
(10,804)
O
70,672
900
77,316
5,943
(596,856)
973
(76,130)
53,586
(42,107)
9,712
3,267
9,785
24,850
55,580
39,877
7,520
Cumulative
Net Cash Net Cash
Flow
Flow
(667,880) (667,880)
(81141
1) (749,291)
(1 0,804) (760,094)
69,772 (690,323)
71,373 (618,949)
(597,829) (1,216,778)
(129,717) (l,M6,495)
(51,819) (lI398,3l4)
(6,518) (1,404,832)
(30,730) (1,435,562)
32,357 (1,403,205)
The results of the disaster scenario are aven in Table 16. A resulting cumulative net cash
flow of (51,403,205) is observed at the end of the LO year horizon, resulting in a payback
period well in excess of 10 years. The NPV under the disaster scenarïo $2 11,495. The
IRR is impossible to cdculated due to al1 negûtive cash flows. The detailed'effects of the
disaster can be seen in the cash flow schedule (Appendix C, Table C-1). Operating Ioans
are required to cover cash short f d s during the fmt two years, and during years 5 through
9 following the moaality. The effects on net income can be observed in the income
statement (Table C-2). As a result of hi& inflation, a learning curve associated with the
first three years of operation, and a diesff in year 5, the veriture never fully recovers, and
at the end of the 10 year projection is economically unviable.
7.0 Risk Assessrnent
During the financial analyses, a number of risks and critical factors presented themselves.
This section will examine some of the more pertinent factors that should be monitored
during the course of operation of the proposed project.
1. The hatchery is designed for a single species only. Should a catastrophic event occur
(as in the disaster scenario) the fmancial niin of the operation is likely. By producing
more than one species, the hatchery could help protect itself from just such an event
through diversification. A rnuch larger demand for oyster larvae exists on Vancouver
Island (B. Kuigzett, personal communication), therefore the operation would be wise to
consider such an expansion. Other shellfish species worthy of consideration would be
scallops (Puthopecten yessoenîis) and geoducks (P. generosa).
2. There is a trend among some growen toward the purchase of smailer seed (2-3 mm
and 4-6 mm) for nursery culture in Flupsy systems or field nursery uni& (B. Kingzett,
personal communication). Should such a trend become prominent, the market for 6-8
mm seed may become obsolete. Markets for seed would exist, however, selling seed at
smaller sues would result in decreased revenues.
The company would have to
concentrate on supplying smdler seed, while at the same tirne reducing its capitd
investment in nursery equipment necëssary to grow seed to the Iarger 6-8 mm size. As
the area designated for culture is projected to double by the year 2005, it is IikeIy that the
decreased sales revenues may be off-set by increased numbers of sales of smalIer seed to
more producers. The company would be well advised to carefully monitor this trend, as
decreased selling prices have betn shown to have a dramatic effect on the financial
stability of the operation.
3.
Experimentation involving the mass setting of larvd clams directly ont0 beach
substrate is currently being undertaken' in BC (Rob Saunden, Island Scailops Ltd,
personai communication).
Depending on the success of these experiments and
acceptance by clam farmers, the operation should carefuUy monitor market trends in the
purchase of smaller or larvd clams. One of the hatchery operators on Vancouver Island
is concerned by this trend, and the possible consequences it rnay have on sales. In light of
this however, the operation should be willing to aggressively follow this trend, as the
farrner would be assuming the risk of larval settlement. In al1 likelihood, only one or two
hatcheries would be required to supply the larval needs of the industry, therefore it is vital
that the company aggressively pursue this trend should it continue. In addition, by selling
larvae ready to set, the hatchery would also benefit by eliminating the capital-costsof its
nursery.
4. The proposed operation aiso has the disadvantage of market penetration. Two small
scale hatcheries are currently in operation on Vancouver Island, with the majority of seed
being imported €rom Californian hatcheries. As a result of this, many growsut operators
are likely to have entered into a cornfortable relationship with their supplier. The one
advantage that the operation possesses (over the Californian hatcheries) is the production
of seed conditioned to locd grow-out environments. For such a iarge scale proposition,
the compiny would have to enter into supply agreements with local growers. Such an
undertaking would require a large marketing effort prior to construction of the facility.
5. As demonstrated in Table 14, the operation is very sensitive to downward shifts in
selling pnce, With this in mind, the company will have to concentrate on keeping its cost
of production dom. This will become especialIy important should the trend toward
nursery rearing by grow-out opemtors become more prevalent.
6. A similar sensitivity to decreased levels of production was aIso observed (Table 15).
As the area for clam culture is projected to double within the next 10 years, the company
would be in a good position to capture this increase in market space through an active
marketing program, thereby offsetting any potential decrease brought about by selling a
smaller sized product.
7. A leaming curve and its effects on the cost of operations should dso receive attention.
Management's ability is likely to manifest itseif on survival levels of larvae and spat, or
through production costs (Thumberg and Adams, 1990). More experienced managers
will likely result in increased sumival of larvae and decreased costs. A less expenenced
manager is likely to have the opposite effects. Thus, the hiring of a qualifieci manager, or
time spent leaming about production aspects before the investrnent would be worth the
added expense.
8. Disease and water quaiity concems are also of paramount importance to the hatchery.
Site selection for the hatchery should meet those critena laid out in Appendix B. By
seIecting only sites within the optimum parameters, larvae are less likely to be stressed
during hatchery rearing. Along with maintaining strict water qudity guidetines there
should be a cornmitment to hygiene and disease prevention. As evident from the disaster
scenario, a complete mortality heralds financial min for the hatchery. Mesures to ensure
disease prevention and spread must be in place.
8.0 Summary
This prelirninary analysis of a commercial scale Manila clam hatchery on Vancouver
LFland suggests that it is possible both from technical and financial perspectives. The
technical aspects of Manila clam husbandry have been apparent for more than the past
two decades, and research continues to make improvements. The dissemination of
information pertaining to clam aquaculture in the province of British Columbia is
excellent, thus further aiding the future of the industry. With a projected decrease in
naturai stocks and sustained (if not increased) demand, the future for Manila clam
aquaculture looks bcight. Tn British Columbia, there are currently 400 ha of foreshore
lease that are designated for clam aquaculture. Of these 400 ha, approximately 200 ha are
non-productive ground or classified as oyster leases. Within the remaining 200 ha, less
than 100 ha are currently being fanned. This results in a current estimated demand of
125,000,000 seed clams. The remaining areas are expected to come into production
within the next 4 to 5 years, thereby doubling the current production. Following this, a
projected doubling of clam designated areas is expected by the year 2005.
The financial analyses conducted on the proposed hatchery indicate that such an
undertaking is only just feasible from an economic standpoint. Should the hatchery
operate within a stable environment, it will generate a profit and be a commercially viable
operation. Dunng the course of the analyses, several key factors were identified that may
have a profound effect on the viability of the operation.
Of particular interest are the operation's sensitivicy to decreases in selling price and LeveIs
of production. Should the operation experience decreased levels in either one of these
areas, it quickly becomes non-viabte Crom a commercial perspective. A decrease in the
levei of production or selling price by 25% would be a disasirous occurrence for the
hatchery. This is the result of a reliance on a singe species, and large amounrs of capital
tied up in hatchery and nursery assets. ùi an attempt to combat this sensitivity, the
hatchery should diversifi its production to include other molluscan larvae.
The trend toward the purchase of smaller seed or larvae by some operators must be
carefully monitored by the Company. Should the trend become the nom, revenues will
decrease as a result of selling seed at a smaiier size. This decrease in revenue would best
be countcracted by an intensive marketing pmgram during the proje=ted increase in clam
culture areas.
Overail, the proposed project is barely economicaily viable, and displays areas of extreme
sensitivity to price reduction and production level decreases, Particular care must be paid
to the above mentioned key-points in order to ensure the economic success of the
proposed hatchery.
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Appendix A
Table 1. Microorganisms and parasites reported to cause disease in clams of the genera
Tapes, Ruditapes. and Venerupis (PiUard et al, 1994).
Patho~en
Micrwrgaaisms
Rickettsiae
Protoz~
Apicomplexa
cl. Perkinsea
Perkinsus
CI. Sporozea
ss. cl. gregarinia
g. Nematopsis
S. cl. Coccidia
Pseudoklossia pectinis
Pseuùoldossia glomerata
Acestopora
Haplosporidium tapetis
Minchhia tapetis
Ancistnmr
Boveria, Proboveria
Thigmophrya bivalvorium
Pelecyophrya tapetis
Metazoans
Cnidaria
Eugymnmthea Uiquiiina
Turbellaria
Paravortex scrobicuiuriae
Convulutajapunica
Trematoda
Bucephah baeri
B. haiemeanus
Clams species (localitv)
~arasitizedoreans
Tapes decussatus
T. philippinanun
T.decussatus
T.semi-decussatus
Digestive gland and gills
Gills
Byssus and shell
T.decussatus
T. puilasaa
T.fl0ridu.v
T.jloridus
T. virgineus
Kidney
Visceral ganglion
T.decussatus
T.decussatus
Digestive gland
Digestive gland and gills
Tapes sp.
T. decussatus
T. pullastra
T.aureus
Giiis
Gills
Gills
T. decussatus (Italy)
Palliai cavity
T.decussatus (Itaiy)
Intestine
Intesthe
T. philippinarum
T. aureus
T.aureus (Italy)
T.decussatus (France)
T. pullastra (France)
T. rugatus (Black Sea)
Digestive gland
Table 1. (continued)
Pathogen
C. latra
C.pectirzata
C.pennata
Gymmnophaiusfossarwn
Cercaria scn'venensis
Parvatrema sp
P. timondavidi
Lepocreadium album
Himasthia elongara
H. ambigua
H.quissetemis
Cestoda
Tylocepham sp.
Copepodk
Mytilicoùt intesturalis
Ostrùzcola koe
Modiolicola bifUia
Conchy&mïs quintus
Cimedia
Malacolepas conchicuia
Decapoda
Pinnothetes latissimus
Pantopoda
Nymphonella tapetis
Species ( T ~ ~ a i i t v )
T.decussatw (France)
T.pullastra (Europe)
T.decuisatus
T.aureus
Parasitized oreans
Gonads
Gonds
Gonads
T.wgatus (France)
T.decussatw (France)
Pailial cavity and rnantle
T, aureus (France)
Palliai cavity and manile
T.romboides (France)
Mantie
T.pullastra (Scotland & Nonvay)
Palliai cavity and rnantle
T.philippinnrum (lapan)
T.philippinana (Japan)
T-decussatrcs
Pallia1 cavity and mantle
T.aureus
Palliai cavity and mantle
T,decussatus
T.auresu (France)
Foot
T.decussatus
Pallia1 cavity and mantle
T. pullamru
T.decwsatus
Gills
T.philippuianrm
Foot
T.semi-decussatus
Digestive gland
T.decussatus
T.philippinanan
T.philippinanun
GUS
T. philippinanun
Intestine
Gills
Gills
T.mitis
T.philippinanun (Japan)
Pallia1 cavity
Table 2. Synopsis of diseases of clams focusing on Tapes (Bower et al, 1994).
Eückettsia-like and Chlamydia-like organisms
Scientinc name (or taxonomie dfibtion): intracellular organism belonging to the
Rickettsiales.
Host: many species of cIarns
Geography: global
Impact on Host: infection usuaüy light and not associated with disease
Control: no known control or prevention
Hinge Ligament Disease of Juvenile Clams
Cytophaga-like bacteria (CLB)
Host: Juvenile Mercenana mercenaria, Tapes philippinam and Siliqua patula
Geography:ubiquitous
Impact: breakdom of hinge ligament impedes normal respiration and feeding, often
allowing secondary infection.
Control: difficult due to ubiquitous nature. Disease bas Little or no effect on healthy
growing juveniles.
Brown ring disease of Manila clams
Vibrio sp.; Vibrio PI isolate
Host: Tapes philippina~n
Geography: West coast of France and possibly Spain
Impact: bacterial infection of the mantle edge resulting in a brown &posit of organic
materiai. Has caused mass mortalities in cultured clam beds on the W e s t coast of
France.
Larval vibriosis or Bacillary necrosis
Vibrio anguillamrn, Vibrio alginulyticus
Host: Mercenaria mercenaria, Tapes philippinanun and other cuIaired bivalve larvae
Geography: ubiquitous
Impact: systemic infection of the sofi tissues of the larvae, resulting in necrosis and
death.
Control: difficult due to ubiquitous nature. Often related to poar husbandry.
Clam Perkinsus disease
Perkinsus atlanticus. Perkiwus sp.
Host: Tapes dect.usutus, Venerupis aurea, Tapes philippinam
Geography: Portugal, Spain, Mediterranean Sea
Impact: milky white cysts on gus, foot and mantle. High mortalities
Control: no known methods of control or prevention.
Table 2 (continued)
Parasitism by gregarines
Nematopsis veneris, N. ostreanun. N. schneideri and other species of the family
Porosporidae
Host: Tapes philippinarum, Cardium edule. C.lamarki, Smcavn rugosa Tellina spp,
and Protothaca staminea
Geography: ubiquitous
Impact: most frequently observed within the gills, associated with a focal, benign
hemocyte infliltration, without significant health treats
Control: no known control or prevention (due to part of the He cycle occuring in the
lumen of marine arthropods).
Haplosporidian infection of clams
Haplosporidiwn tapetis9H.sp.
Host: T.philippinarum, T.decursatus
Geography: France, Portugal, Spain, and Oregon
Impact: low prevalence of infection ( ~ 4 %with
)
minimal pathogenicity. No mortalities
associcated with this disease, however, highly pathogenic to oysters on the east
coast of US.
Control: no known control or prevention
Sphenophyra-like ciliates
Sphenophyra dosiniae, S. cardii and other unidentifled species in the order Rhynchodida
Host: T.philippinanmi, Myu a r e ~ r i aM.
, tmncutu and a wide range of other bivalves
Geography: ubiquitous
Impact: large nurnbers appear without any adverse effect on the Host. No mortalities
associated thus far with this type of infection.
Control: control or prevention impractical
Gill trichodinids
Trichondina spp.
Host: T.philippinarum, Mya arenaria, Macoma balticu
Geography: thought to be ubiquitous
Impact: most infections are imocuous, however, heavy infections in individuals less
than a year old can result in eoiaciation and mortalities
Control: no known control or prevention
Turbellaria of clams
Rhabdocoela of the family Graffillidae
Host: numerous species of clams
Geography: global
Impact: no known effect on Host. Thought to be midway between endocornmensai and
parasitic
Control: impractical
Table 2 (continued)
Trematode rnetacercarial infection of clams
various species of the Digenea families
Host: T.philippinanun, T.dectïssutw, T.aureus, Mya arenuria, Mercenaria mercenaria
and various other bivalves
Geography: giobal
impact: usually innocuous, however, some species have been reported to cause a change
in clam behaviour, dong with severe tissue damage and eventuai mortality. No
pathology has been reported with the various species found in Canada
Control: impracticai
Mytilicola disease, Red worm disease
Mytilicola intestrnalis (Copepoda)
Host: T.decussutus, Mucoma baltica and a wide range of other marine bivalves
Geography: Europe
Impact: no known paihology on the Host
ControI: nt, known rnethods of conml or prevention
Mytilicola parasitism, Red worm
Mytiliccila orientalis (Gopepoda)
Host: T.p h i l i p p i n a m Pr~tothacasraminea, Saxidomus gigcrnteus and a wide range of
other marine bivalves.
Geography: West coast of North Arnerica and France
Impact: no hown paihology on Host
Control: no known methods of control or prevention
Oyster crab, Pea crab
Pinnotheres pisum, P. maculanis, P. pholadis, Pinnixa faba, Fabia subquadraru
(Decapoda: Pinnotheridae)
Host: T. philippinarum, Protothaca sîuminea, Panope generosa, Macoma nasata, Mya
arenaria and Spisulu solidissima
Geography: eastern and western USA, British Columbia
Impact: mantie may contain several crabs, thereby reducing market valve. No direct
evidence of pathoiogy observed.
ControI: precautions to prevent their introduction
Appendix B. Biophysicai Criteria for Manila Chm Culture
The following biophysical i l t e n a are required for Manila clam growth and
survivai:
temperature: range for growth = 13 - 21 OC, with 160C k i n g the optimum; these
temperatures are found 4 - 6 months of the year dong the southern BC Coast.
salinity - range for growth = 24 - 31 ppt; optimum = 28 ppt
-
good quality food the exact quality and quantity is unknown, however, proximity to
good oyster production areas will likely facilitate good clam growth
substrate - a combination of mud, gravel, sand, and shell resulting in a fairly firm
substrate
tide height - mid to upper intertidal zone (1 - 2.5 m above zero tide mark)
-
minimum air temperature areas in whkh low air temperature result in the fieeWng of
substrates should be avoided Wide spread moaalities have been observed following
2 -3 weeks of air temperatures of -10 to -170C.
predators - areas with large populations of diving ducks, starry flounder (Platichthys
stellatus), crabs (Cancer productus), moonsnaiis (Polinices lewisi) and seastars
should be avoided.
water quality - areas wiîh toxic algai blmms, sewage and toxic pollution should be
avoided.
source: Chew, 1989; Anon., 1990b
Appendlx C
Table C-1, Disaster Scenarlo and the Resultlng Effect on Operational Cash Flows
Beginning Cash Balanes
Cash Ricdpb
$
180,000
182,195
217,766
293,058
381,180
31,351
81,624
137,212
195,037
237,133
From Operations
Ornier's lnvestment
Bank Loan
Toîal Cash lnllow
Caah Outflaw
Capifai costs
Varlable cosls
Flxed cosis
TOTAL OISBURSEMCNTS
OperaUng Loan
payment pfinclpal
interest
-
Pm-îax Bank Balance
lncome Taxer, (5W)
EndlngCanh Balance
$
180,000
182.195
217.766
293,058
381,180
31,351
81,624
137,212
195,037
237,133
288,841
Summary of debt outstandlng
Long-terni debt
Balance
$
551,122
496,010
440,898
385,785
330,673
275,561
256,564
199,217
139,869
1 15,667
52,415
O
14,805
O
O
D
O
O
30,820
O
12,176
6,132
O
7,136
O
O
O
21,917
O
7,777
Operaling debt
Balance
Interest
O
Appendix C
Table C-2. Disaster Scenario lncome Statement
Year 1
Year 2
Year 3
Year 4
500,000 500,000 500,000 500,000
Revenues
Year 5
Year 6
Year 7
Year 8
Year 9 Year 10
O 500,000 500,000 500,000 500,000 500,000
Cost of Goods Sold:
Electricity
Lab Supplies
Technicians
Pump maintenance
PacWng
Selllng
65,000
6,500
85,800
5,200
6,500
13,000
60,000
6,000
79,200
4,800
6,000
12,000
55,000
5,500
72,600
4,400
5,500
11,000
52,000
5,200
68,640
4,160
5,200
lO,4OO
54,080
5,408
71,386
4,326
O
O
56,243
5,624
74,241
4,499
5,304
10,608
77,211
4,679
5,410
10,820
60,833
6,083
80,299
4,867
5,518
11,037
Total COGS
182,000
168,000
154,000
145,600
135,200
156,520
162,463
168,636
l75,O!il
181,715
Gross Margln
318,000
332,000
346,000
354,400
(135,200) 343,480
337,537
331,364
324,949
318,285
5,800
3,900
85,975
68,238
57,200
1,300
1,872
5,200
3,120
7,800
7,800
12,120
4,800
3,600
79,362
62,989
52,800
1,200
1,728
4,800
2,880
7,200
7,200
11,188
4,800
3,300
72,748
57,740
48,400
1,100
1,584
4,400
2,640
6,600
6,600
O
4,800
3,120
68,780
54,591
45,760
1,040
1,498
4,160
2,496
6,240
6,240
O
4,800
3,245
71,531
56,774
47,590
1,082
1,558
4,326
2,596
6,490
6,490
O
4,800
3,375
74,392
59,045
49,494
1,125
1,620
4,499
2,700
6,749
6,749
O
4,000
3,510
77,368
61,407
5 1,474
1,170
1,685
4,679
2,808
7,019
7,019
O
4,800
3,650
80,463
63,863
53,533
1,217
1,752
4,867
2,920
7,300
7,300
O
4,800
3,796
83,681
66,418
55,674
1,265
1,822
5,061
3,037
7,592
7,592
O
4,800
3,948
87,029
69,075
57,901
1,316
1,895
5,264
3,158
7,896
7,896
O
260,326
239,747
209,912
198,724
206,481
214,548
222,938
231,664
240,739
250,176
N d Profit before taxes
57,674
92,253
136,088
155,676
(341,681) 128,932
114,599
99,700
84,211
68,109
Tawes (at 50%)
28,837
46,127
68,044
77,838
64,466
57,300
49,850
42,105
34,054
N d Profit after taxes
28,837
46,327
68,044
77,838
64,466
57,300
49,850
42,105
34,054
58,493
5,849
63,266
6,327
83,511
5,061
5,628
11,257
65,797
6,580
86,851
5,264
5,741
11,482
Exponnem:
Vehicle Lease
Insurance
lnterest
Depreciation
Wages
Site maintenance
Property taxes
Vehicle
HeatlFuel oil
Mlscellaneous
Suppiies/expendables
Contingency Fund
Total Expense
Accumulated Protitsl(Loss)
(341,681)
TEST TARGET
(QG~)
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