Download Section 1: The Current Situation

Section 1: The Current Situation
24
This section outlines the current situation of New Zealand seaweeds by providing the best
available information across the SOIs three broad outcomes:
♦
Health of the aquatic environment is protected
♦
Best value is able to be realized
♦
Credible fisheries management
25
Most seaweeds belong to one of three groups based on colour: the browns (phaeophytes),
reds (rhodophytes), and the greens (chlorophytes).
26
The brown seaweeds are the largest and most conspicuous of the three seaweed groups and
include kelps. Green and red seaweeds are typically smaller, and more frilly and delicate in
structure. Conflict – one plural, one singular 27
Seaweeds generally comprise of three main parts: a holdfast, a stipe, and blades (or fronds)
– refer to Figure 2 for illustration of each seaweed part and lifecycle. The stipe can be of
considerable length to enable the blades to reach shallower water where light intensity is greater.
Stipe is usually unable to support the weight of the blades out of the water. Green and red
seaweeds are typically more filamentous or sheet-like in structure.
28
The life history comprises two main phases – the predominant (conspicuous) sporophyte
phase (stage that produces asexual zoospores) and the inconspicuous gametophyte phase (stage that
bears sexual gametes). There are species-specific variations in life history.
Figure 2:
A stylised diagram of the life history of a seaweed (illustration obtained from NIWA
website at www.niwascience.co.nz)
9
HEALTH OF AQUATIC ENVIRONMENT PROTECTED
29
An understanding of the nature, diversity, stability, productivity, and the extent of
New Zealand’s seaweed resources provides information to address fishing and non-fishing impacts
on the aquatic environment.
30
Seaweeds are structurally important components of the aquatic environment. They play a
vital role in the ecology of the aquatic ecosystems giving structure and complexity; providing
substrate, food and shelter to many marine organisms; and contributing to the nutrient cycling of
both beaches and the surrounding coastal waters. Seaweeds are critical for the recruitment,
dispersal and protection of many commercially important fisheries such as rock lobster, paua and
mussel spat.
Managing the Effects of Fishing
31
The activity of fishing can impact the aquatic environment in a variety of ways. For
example, bottom impacting fishing methods (eg, trawling and dredging) can alter the structure of
the seafloor and impact associated plants and animals, and fishing nets or lines can inadvertently
capture or injure marine mammals or seabirds. The Fisheries Act 1996 outlines several
environmental principles that must be considered when making decisions relating to the use or
sustainability of fisheries resources like seaweeds. These include:
♦
maintaining biological diversity (biodiversity) of the aquatic environment
♦
protecting habitats of particular significance for fisheries management.
♦
maintaining associated or dependant species above a level that ensures their longterm viability
32
In addition, in 2005 the Government launched its Strategy for Managing the Environmental
Impacts of Fishing (SMEEF) The SMEEF proposed the development of a set of standards for
defining acceptable limits of effects of fishing on the aquatic environment. The development of
these performance standards is now underway. The following sections examine seaweed fisheries
in relation to the environmental principles and linked performance standards. Fishing impacts on
the seafloor (benthic impacts) are discussed as a separate topic as these impacts span both
biodiversity and habitats of particular significance to fisheries management.
Biological diversity
Performance standard: Draft standard is to identify and maintain biodiversity in the
aquatic environment.
33
Section 9 of the Fisheries Act 1996 outlines several environmental principles that all
persons exercising or performing functions, duties, or powers under the Act, in relation to the
utilisation of fisheries resources or ensuring sustainability, shall take into account. One of these
environmental principles is to maintain biological diversity of the aquatic environment.
34
New Zealand’s marine biodiversity is to be protected by establishing a network of marine
protected areas that is comprehensive and representative of New Zealand’s marine habitats and
ecosystems.
10
35
The Government aims to achieve a “target” of 10% of New Zealand’s marine environment
protected by 2010. MFish and the Department of Conservation are jointly responsible for
developing and implementing marine protected area policy to achieve this target. There are a
number of marine protected areas throughout New Zealand, including various closed areas and
31 marine reserves.
36
New Zealand has an extensive marine algal flora of about 1 000 species. Exposed reefs,
channels and pools have the greatest diversity of seaweed species. Harbours, fiords, and sounds
share some of this rich flora. Sheltered lagoons, mangroves, inlets and estuaries where the salinity
is reduced by freshwater have a very different seaweed flora. In many of these habitats, a flowering
plant commonly called seagrass (Zostera spp.) may be very extensive. Each of these natural
habitats has a typical association of seaweed species that commonly vary in composition from north
to south.
37
Seaweeds are critical for the recruitment and protection of many commercially important
finfish and shellfish fisheries. Attached seaweeds are structurally important components of the
marine environment and support high biodiversity by providing habitat, shelter and food, as well as
affecting wave flow and energy. Many important finfish (eg, butterfish, moki) and shellfish
(eg rock lobster, paua, kina) species generally associate with reef areas that predominate with large
kelp forests. However, the interactions and associations between seaweeds and higher-order
species are not well understood.
38
Free floating seaweeds play an important role in the recruitment and dispersal of other
organisms. Beach-cast seaweeds provide habitat and food for a diverse ecology of marine and
terrestrial organisms, as well as being key sources of nutrient cycling within the aquatic
environment. It is estimated that up to 25% of the annual kelp production may become beach-cast,
and, when not removed from the beach environment, this material can play a significant role in
coastal ecosystems.
39
Each of the three seaweed states has different key implications on biodiversity. These key
implications are set out in Figure 3.
40
The invasive Japanese seaweed Undaria pinnatifida is found in many parts of New Zealand
(mainly restricted to parts of the southern North Island and throughout the South Island).
This seaweed is known to displace many native seaweed species and has the potential to have
negative implications for biodiversity of both seaweeds and non-seaweed species. There is
presently a prohibition on the commercial harvest of Undaria. Biosecurity New Zealand, however,
is to review this prohibition in 2007 and some commercial harvest may be allowed in the future.
In some areas, regional authorities are taking limited measures to control the spread of this species.
11
Figure 3:
Key characteristics of the three seaweed states and implications for biodiversity
States
Attached
Free Floating
Beach-cast
Biological life-cycle
Biodiversity
ECOLOGICAL
ROLE
CANOPY FORMING
CAN STILL BE
GROWING AND
REPRODUCING
CRITICAL HABITAT
IMPORTANT FOR
RECRUITMENT OF
MANY SPECIES
IMPORTANT FOOD
SOURCE AND
SHELTER FOR
INVERTEBRATES
AND SHORE BIRDS
DISPERSAL OF
SPECIES
STRUCTURAL
IMPORTANCE
MODIFYING WAVE
FLOWS AND
ENERGY
SETTLEMENT
SURFACE FOR
MUSSEL SPAT
REFUGE AREAS
FOR JUVENILE
AND LARVAL FISH
NESTING
MATERIALS FOR
SEABIRDS/WADERS
POTENTIAL BEACH
BUILDING
MATERIAL
Habitats of particular significance to fisheries management
Performance standard: Draft standard is to identify and protect habitats of particular
significance for fisheries management.
41
Protecting habitats of particular significance to fisheries management is one of the
environmental principles outlined in s 9 of the Fisheries Act 1996.
42
Seaweeds are found in all habitats of significance, including spawning and nursery areas,
estuaries, and areas of particularly high biodiversity.
Associated or dependent species
Performance standard: Draft standard is to identify and maintain associated and
dependent above a level that ensures their long-term viability
43
Maintaining associated or dependent species above a level that ensures their long-term
viability is one of the environmental principles outlined in the Fisheries Act 1996.
44
Associated or dependent species means any non-harvested species taken or otherwise
affected by the taking of any harvested species. This can include protected species such as marine
mammals, seabirds, and reptiles.
12
Protected species
45
There are no direct associations between seaweed harvesting and fishing-related mortality of
protected species. However, there are indirect associations between seaweed harvesting and
several protected species, as presented below.
Seabirds and reptiles
46
A wide range of invertebrates (eg, amphipods, isopods, copepods) are found living on
beach-cast seaweeds. These invertebrates are an important food source for some protected birds
and reptiles. For example, kiwi on Stewart Island are often found foraging for amphipods and
isopods amongst beach-cast seaweeds. Although there are no quantitative New Zealand studies on
the use of seaweeds by birds, overseas studies suggest that beach-cast seaweeds have a significant
effect on density and abundance of some shorebird species. These studies indicate a positive
correlation between beach-cast material abundance and seabird densities.
47
Many birds use beach-cast seaweeds for nesting either directly within the wrack material or
to supplement other nesting material. The removal of beach-cast seaweeds from areas adjacent to
seabird breeding colonies could affect the breeding success of some seabird species.
48
Several native skink and gecko species also feed on the invertebrate communities that
inhabit beach-cast seaweeds. A reduction or removal of beach-cast seaweeds may have negative
implications on these species.
Benthic impacts
Draft standard will define the permissible level of impact of fishing methods on
each habitat identified.
49
Benthic impacts are impacts on the animals and plants living on, or attached to, the bottom
of the sea, lake or river from high water mark down to the deepest levels (ie, the benthos).
50
There are currently no New Zealand studies to assess the direct impacts of seaweed
harvesting on the benthic environment. Nearly all commercial and non-commercial seaweed
harvesting is currently undertaken by handgathering methods only (ie, picking, raking, scooping).
Some limited cutting of bladder kelp (Macrocystis) occurs on the Chatham Islands. Some trials
have also been undertaken in Akaroa Harbour to investigate the effects of floating mechanical
harvesters on bladder kelp.
51
Areas with high kelp biomass (commonly referred to as ‘forests’ or ‘stands’) form important
structural components in inshore and coastal areas. These kelps typically modify wave flow and
energy; hence their removal can have large-scale implications to the physical structure of inshore
areas, largely through erosion and reduced beach-building. A large-scale harvest of kelps could
increase erosion in localised areas and impact on beach building processes.
52
Research undertaken in Australia suggests the following potential adverse effects may arise
from the large-scale removal of beach-cast seaweeds from an area.
a)
Loss of nutrients from the inshore and coastal systems through the nutrient recycle
process.
13
b)
Removal of an important food source and shelter for invertebrate and seabirds.
c)
Loss of nesting material for seabirds.
d)
Removal of potential beach-building material, as beach-cast seaweeds are effective
at trapping wind-blown sand and reducing erosion.
53
Conversely, removal of infestations of aquatic seaweeds in ponds and lakes that have high
nutrient conditions could provide some positive outcomes for biodiversity and the benthic
communities in such habitats.
Other resource users
54
Regional Councils manage the effects of land-based activities on the marine environment
such as changing land-use (ie, forestry, town development, etc.). Increases in nutrient run-off into
coastal waters from agricultural development may lead to greater proliferation of seaweed beds.
Increased sediment load within localised waters may lead to seaweed bed die-off or reduced
growth, productivity, etc. through increased water turbidity (eg, reduced light penetration) and
smothering.
55
Several local authorities and regional councils regularly remove decomposing/rotting
beach-cast seaweeds from popular beaches throughout New Zealand for sanitation and aesthetic
purposes. In addition, power companies regularly clean up freshwater algal build-up round turbine
intake tubes.
56
Seaweeds are increasingly being on-grown on marine farms in many parts of New Zealand.
The effects of seaweed farming on the aquatic habitat are unknown. Seaweed farming may be
beneficial by increasing productivity (ie, greater concentrations of chlorophyll within the water)
and increasing number of reproductive spores. However, decaying seaweeds under farms may have
negative effects within localised areas.
Specifying Limits on Fishing Activity
Harvest Strategies
Draft harvest strategy standards (s 13 or s 14)
57
As seaweeds are managed outside the Quota Management System (QMS), there is no prescribed
target level for each seaweed stock.
58
MFish has not imposed a total catch limit for any individual seaweed stock due to the current
low level of seaweed catches.
59
The principle harvest strategy for seaweeds is to provide for utilisation while ensuring
sustainability.
14
Stock assessment information
Biological characteristics
60
Table 1 below provides an overview of the lifecycle, growth, preferred habitat and
distribution of the main seaweed species. More detailed biological and stock assessment
information is provided in Appendix 1.
15
Table 1:
Species
Macrocystis
pyrifera
Key biological characteristics of the main seaweed species
Seaweed
group
Brown
Life cycle
2 phases: Conspicuous
sporophyte kelp phase,
microscopic gametophtye
phase
Growth
Lessonia spp.
Brown
Durvillaea
antarctica
Brown
Porphyra
species
Red
2 phases: Conspicuous
sporophyte kelp phase,
microscopic gametophtye
phase
Direct life history with
separate male and female
seaweeds producing eggs
and sperm.
Reproduction from late
autumn to early spring
Large conspicuous
gametophyte phase and a
small sporophyte phase
Winter annual
Perennial
Grow up to 20 m high
Worlds fastest growing
plant, up to 0.5 m/day
Temperature and light
limited
Maximum biomass occurs
in winter
Perennial
Grow up to 1 m high
Habitat type
Found on rock in calmer
bays, harbours and offshore
reefs
Distribution
Southern North Island at
and south of Castle Point
and Kapiti Island
South Island and Stewart
Island, Chathams and others
Found on rock from low
water spring to sub-tidal on
very exposed coasts
Throughout New Zealand
Plants massive grow up to
10 m but usually 3-5 m high
Seaweed may be 10 years
old
Found on rock forming a
broad zone at low water in
very exposed situations, but
also extending into calmer
bays
Throughout New Zealand
but is most common south
of Cook Strait.
Usually grow ca. 15-25 cm
Some species are epiphytic
Growth and longevity very
species specific
Species specific ranges from
upper intertidal rocks in
moderately sheltered to
open sites to epiphytic on
Durvillaea species
Throughout New Zealand
Species
Gracilaria
chilensis
Ecklonia
radiata
Seaweed
group
Red
Life cycle
An alteration of sporophyte
and dioecious gametophyte
generations
Usually grows ca. 15-25 cm
Forms persistent mats, often
detached from substrate
•
Brown
2 phases: Conspicuous
sporophyte kelp phase,
microscopic gametophtye
phase
Grow up to 1 m or more
high
Growth of recruits inhibited
by high light intensity
Is winter fertile
Grow from 10 – 50 cm
Grows up to 30 cm high
Pterocladia
spp.
Red
Ulva spp.
Green
An alteration of sporophyte
and dioecious gametophyte
generations
Sporophyte releases spores
that grow in to male or
female gametophytes that
are morphologically
indistinguishable from the
sporophyte. The
gametophyte releases
gametes that fuse to form
the zygote that settles and
grows into a sporophyte
Growth
17
Habitat
Found in sheltered sites
frequently in harbours and
estuaries and often in areas
with muddy sands. Grows
attached to shell as well as
on cobbles and rocks, in the
low intertidal zone through
to the upper sub-tidal (to ca.
1-2 m)
Found on rock at and below
low water spring on
moderately sheltered and
exposed coasts
Found on rock at and below
low water spring on exposed
coasts
Found on rock and solid
substrate. Intertidal in
moderately sheltered areas.
Sometimes free-living
Distribution
Throughout New Zealand
Throughout New Zealand
Throughout New Zealand
Throughout New Zealand
Indices of stock abundance and biological information
61
Varying amounts of biological information are available for a number of New Zealand
macro-algae species. However, there is limited, to no, information available in regards to stock
abundance, relative or absolute biomass estimates, catch per unit effort (CPUE) or catch trends for
any seaweed species or stock.
Research
62
Completed research projects on seaweeds include:
Year
2001
Research project
Assessment of Pterocladia lucida at Waihau Bay, New Zealand.
New Zealand Fishery
Gerring, P.K., Andrew, N.L. and A. Dunn (2001). Assessment
Report 2001/72. 23 pp.
2005
Beach-cast seaweed: a review
Zemke-White W L, Speed S R, McClary D J, New Zealand Fisheries
Assessment Report 2005/44 August 2005
Total allowable catch
63
There are no total allowable catches (TACs) for any seaweed stock. Annual or seasonal
commercial catch limits do not apply to any seaweed stock, and no explicit allowances have been
made for non-commercial fishers.