Download Coastal fish populations - Centre for Marine Biodiversity

Coastal fish populations –
do we know where the fish are?
Topics to Address:
• What fish are using the inshore and how are they using it?
• How is our knowledge of species life histories, distribution
and abundance biased by our sampling (spatially,
temporally)? What are we missing?
• Are there specific areas that are important as:
• Spawning areas? Migratory routes? Nursery areas?
• For which species do we have evidence for population
structure - Can we extrapolate to other species?
• Has use of inshore habitat by fish changed?
Some fish remain inshore.
Some are
seasonal
migrants
- or just
passing
Through
Some spend some life-stages inshore and others offshore
Annual monitoring
• DFO research
vessel survey has
annual coverage
since 1970, but
misses much of the
inshore – too rough
to trawl.
• Detailed biological
sampling, but high
variability in
estimates for
benthic fish which
go under the net.
• Changes in relative
inshore abundance
are not detected.
ITQ Survey
• About 184 stations
sampled annually.
• Good sampling off
SW Nova Scotia.
• No inshore stations
between St.
Margarets Bay and
Shelburne.
• Catch includes most
fish encountered no space below
footrope, but less
detail recorded in
data for most
species
8°
66°
64°
Cod from ITQ
•
•
•
•
Most cod caught in the Bay of Fundy
Inshore catches highest off Cape Sable
In eastern 4X cod are must abundant inshore
Age 0 and 1 catch highest inshore
Winter flounder
from ITQ
• Found only in depths <50fm
• Few in St. Margarets Bay
Dogfish from
ITQ
Caught all around Nova Scotia.
Most abundant in Bay of Fundy and mid-depths on the
Scotian Shelf.
4VsW Sentinel
• Covers eastern Scotian Shelf, with good inshore sampling.
• Catch restricted to fish that take a commercial size hook
• Limited biological sampling for most species
Cod
• Caught throughout the inshore area
• Catches are largest inshore
• Cod dominate the catch
Other species:
Several species combined - same weight scale as cod
Combined weight less than cod at most locations
Most fish are caught off Halifax and near Chedabucto Bay
Fishery Data
• Landing coordinates are only available since about 1996
for fixed gear, 1991 for otter trawl.
• Prior to 1960, landings are recorded by county - primarily
coastal hook and line, which gives a coarse resolution on
location.
• Coastal fisheries were scattered along the entire shore.
• The major fisheries along the shore for cod haddock and
pollock were Cape Sable-Shelburne, St. Margarets Bay Halifax, around Chedabucto Bay and Sydney Bight.
Longline landings in summer 2003
• Landings data
provide some
information on
species composition
inshore.
• Cod, haddock and
halibut caught
inshore, with small
amounts of other
species.
• Currently two areas
with active fisheries.
Otter trawl landings - 1991
• Broad area covered, but limited coastal fishing
• Little observer coverage, so limited information on noncommercial species
Otter trawl landings - 2002
• Very little coastal fishing outside of the Bay of Fundy in
recent years
• Little fishing east of Halifax due to management restrictions
Otter trawl species composition in 1992
Inshore catches
were primarily
winter flounder and
cod.
Very little observer
coverage, so only
data on
commercial
species.
Inshore pollock catches
• Inshore fishery was extensive
• Gilllnet caught 000's tonnes annually in fall.
• Pollock caught in mackerel traps in St. Margarets Bay (4060cm); large pollock also caught in trapnets.
• Little inshore catch of pollock now.
30
pollock lengths (cm)
25
20
15
10
5
0
73
79
82
85
88
91
94
97
100 103 106 109 115
35000
Cod fishery
5Y
4Xu
30000
4Xs
4Xr
4Xq
25000
4Xp
4Xo
4Xn
20000
4Xm
15000
10000
5000
0
1968
1971
1974
1977
1980
1983
1986
1989
1992
1995
1998
• Prior to the arrival of otter trawlers in the early 1960’s, inshore
hook and line was the bulk of the fishery.
• Inshore catches (4Xmo) remained dominant until the 1990’s.
Haddock fishery
• Very little inshore haddock fishery now
• Handline fishery was active around Cape Sable until late
1990’s
• A tagging study in the 1930’s used fish caught in the haddock
trap fishery, which was active in a number of sites from St.
Marys Bay to Ingonish (May-July).
• Haddock could be seen on the bottom in 2 fm. of water.
Haddock fishing was primarily coastal in the early 20th century
In some areas this was seasonal while others
(Passamaquoddy Bay) it was year-round
Mackerel Landings by Area
• Mackerel migrate through inshore Nova Scotia
• There is an active fishery in some areas, and recreational
fishing is widespread
98
8 613
4Ra
4Rb=
2 372
1
4To
11 400
C
4Tu= 1
4Tn=
4Tm
220
4Tl=
4 297
4Rd
4Tg= 1 966
4Xo=
1 503
3Lj=
4Vu= 2
Ï-P-É / PEI
4Vn= 9
4Th=
208
4Wd= 47
se
cos
4Wk=
É
2
4Wh=
elle
2
v
4Xm=
u
o
1
N
1 854
B
9
3Lb=
29
3Pn=
21
tia
Sco
a
ov
/N
4Xr=
4Xq= 15
12
4Tf= 976
266
4Tj
Terre-Neuve /
Newfoundland
9 534
4 917
3Ki= 1 572 3La=
4Rc=
677
NouveauBrunswick /
New
Brunswick
3Kd
3Kh
D
10
3Lq= 13
Tuna show up in coastal areas where they feed on mackerel
and herring
Dogfish landings
The main coastal hook and line fishery recently is for dogfish
Dogfish are not a recent arrival in inshore – In 1930 they were
abundant around Campobello and reportedly restricted fishing
for hake until mid-November
Main remaining fishing areas are around Cape Sable and off
Halifax with others important in past
HERRING SPAWNING LOCATIONS
47
46
d
an nt
n
e
ter
as pon
E
m
,
on g Co
t
e
r
in
e B awn
p
Ca Sp
ks
tal ore
s
an
a Sh
o
B
C th
lf
u
he nent
o
S
S
o
n
tia omp
o
C
Sc
re ning
o
h
w
fs
Of Spa
45
SW Nova
Spawning
Component
44
43
42
G
41
70
in
awn
p
S
nk
s Ba
e
g
r
eo
69
68
67
nent
o
p
m
g Co
66
65
64
63
62
61
60
59
Gillnet catches for 2005
Herring
gillnet
landings
2005
47°
Catch dates from Jun-09-05 to Oct-08-05
Total Catch - 3490 t
Total No. slips - 513
Plotted catch - 3489 t
Catches w/o location - 0 t
46°
45°
44°
Gillnet Catch t
10
50
100
250
0
• Few active inshore fishing grounds.
• Herring and herring eggs are a major food source for many
species when available.
• Large winter fishery in Chedabucto Bay in past.
Cod spawning
• Cod spawn in coastal Nova Scotia in fall. Halifax Harbour
spawning was studied extensively in 10-15 m of water.
Tagging studies have
helped uncover
movement patterns
and determine stock
structure
Returns from South Shore cod tagging studies –
limited movement, with most remaining inshore
Some areas had more inshore-offshore mixing
Pollock Tagging
• Small pollock (20-35 cm) tagged in Chedabucto Bay Halifax
hrbr and Cape Sable.
• 1st year returns all local – subsequent years they dispersed
to offshore areas.
48°
47°
46°
45°
44°
43°
42°
Juvenile cod mainly in shallow coastal waters –
lots of things to hide in and under
Juvenile distribution
• Can be difficult to study from standard DFO data collection
– small cod go under the net.
• Haddock are offshore
• Cod, pollock and white hake are inshore
• Small cod prefer eelgrass (lab studies) as do white hake
and have higher survival in this habitat (St. Margarets Bay)
• Beach seining in the 1930’s found cod (3-10cm) in many
locations around Nova Scotia. Less success in 2000 Black rock beach at low tide in eel grass.
• Pollock dispersed through coastal habitats, but prefer areas
with cover.
Stock Structure
• Little known for most species
• Some similarities in growth patterns and tagging study
results for cod haddock and pollock – perhaps stock
structure can be inferred for species with similar life
history?
Conclusions:
• Less fish inshore than in past – inshore fisheries very poor.
• Little annual monitoring inshore – some areas impossible to
sample with standard survey procedures.
• Inshore biomass unknown.
• Surveys which cover inshore collect limited biological data.
• Important Areas?
• Around Cape Sable – cod spawning, juvenile fish, diverse catch
• Around Halifax – cod and herring spawning, has been productive
fishery.
• Sydney Bight
• Mouth of Chedabucto Bay
Some fish remain inshore
throughout their lifespan
•
Some fish are seasonal migrants
– Some species come inshore to feed (Dogfish, large pelagics )
– Some come inshore to spawn (Herring, lumpfish)
– Some spend time in coastal areas for unknown reasons (overwintering
herring in Chedebucto or off Hfx)
• Some spend life-stages inshore
• Coastal area are productive, and have structure for hiding.
Mackerel feed and migrate through
Cod, pollock, winter flounder spawn
Juvenile cod, wh. Hake in eel grass; pollock in rockweed, eelgrass etc.
Coastal fisheries have declined
Juveniles are more difficult to locate than in past