assessment of the icelandic cod stock björn Ævarr steinarsson marine research institute
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Assessment of the Icelandic cod stock
Björn Ævarr SteinarssonMarine Research Institute
Components of adviceComponents of advice(short-term)(short-term)
Data Data analysis Assess. Prediction
Landings
Lengthmeas.
Otoliths
Surveys
Catch innumbers
Indices
Stockassessment
Predicteddevelopm.
of stockand catchLogbooks
CPUE
OtolithsLength m.
Input data
• Catch in numbers by age groups
• Survey indices
• Catch per unit effort (CPUE) from the fleet
Icelandic cod. Landings1906-1996
0
100
200
300
400
500
600
1905 1915 1925 1935 1945 1955 1965 1975 1985 1995
Year
'000
t
Other NationsIceland
CodLandings by gear
0102030405060708090
100
Bottomtrawl
Gillnet Longline Handline Danishseine
%
Distribution of cod catches
Distribution of cod catches
Sampling from landingsSampling from landings
• Allocation
– Samples alloced proportional to landings in each fleet category - Real time.
• Implementation
– MRI staff
– Inspectors from the Fisheries Directorate
– The Coast Guard
• Magnitude
– Annually about 150.000 length measurements and 15000 otoliths for ageing.
CodCatch in number by age groups
05
10152025303540
3 4 5 6 7 8 9 10+
Age
Num
bers
in m
illio
ns
CV 20
Icelandic Groundfish SurveyIGFS
• Annually about 600 fixed trawl stations taken in March all
around Iceland since 1985.
• Performed by 4-5 identical trawlers
• Standarized trawl, trawling distance, trawling speed etc.
• About 50 000 length measured and 5 000 otoliths taken for
ageing
• Gutted and ungutted weight, liver weight, gonad weight,
stomach content anlysis, maturity etc.
IGFS Towing station in spring survey
IGFS- Primary objectives -
• Independent estimate of relative
abundance.
• Annual indices of recruitment.• Various biological parameters.
IGFSTotal biomass index
0
100
200
300
400
500
600
85 90 95 2000Year
Bio
mas
s In
dex
CV 10-16
IGFSRelative abundance index by age groups in 2002
0
10
20
30
40
50
1 2 3 4 5 6 7 8 9 10 11 12
Age groups
Inde
x in
Num
bers
Survey abundance vs number alive in the sea
Number of fish of age a in surveyNu
mb
er o
f fi
sh o
f ag
e a
in t
he
sea
aa qUN
IGFS - COD
Index of 3 years old vs. 4 years old a year later
82
83
84
85
86
8788
8990
91
92
93
94
95
96
97
R2 = 0.8995
0
20
40
60
80
100
120
0 20 40 60 80 100 120
Index of age group 3
Ind
ex
of
age
4 a
ye
ar la
ter
LogbooksExample
Distribution of Logbooks records
Bottom trawl
Shrimp trawl
Longline
Capelin herring
Dragnót
Pelagic trawl
Herring
LogbooksObjectives
• Collecting data to estimate CPUE/Effort
• Behavior of the fishing fleet
• Relationship with fishermen
CPUE vs Biomass
CPUE (tonn/hour)
Bio
mas
s (t
on
nes
) qCPUEB
CODCPUE 1991-2001 by gears
60
80
100
120
140
160
180
91 92 93 94 95 96 97 98 99 2000 2001Year
CP
UE
in
dex
Bottom trawl Gillnet Longline
Distribution of cod catches
Greenland HalibutMain fishing areas
CODCatch in numbers 1991-2000 (Millions)
Yearclass 1988Yearclass 1988
Ár/Aldur 3 4 5 6 7 8 9 10 11 12 13 141991 8.55 25.13 15.49 21.51 25.04 6.36 0.90 0.24 0.13 0.06 0.01 0.011992 12.22 21.71 26.52 11.41 10.07 8.30 2.01 0.26 0.05 0.03 0.01 0.011993 20.50 33.08 15.20 13.28 3.58 2.79 2.71 1.18 0.18 0.03 0.01 0.011994 6.16 24.14 19.67 6.97 4.39 1.26 0.60 0.51 0.28 0.05 0.02 0.011995 10.77 9.10 16.83 13.07 4.12 1.60 0.31 0.18 0.16 0.14 0.03 0.011996 5.36 14.89 7.37 12.31 9.43 2.16 0.84 0.21 0.08 0.07 0.06 0.011997 1.72 16.44 17.30 6.71 7.38 5.96 1.15 0.49 0.13 0.03 0.04 0.021998 3.55 7.71 25.39 20.17 5.89 3.86 2.95 0.50 0.20 0.06 0.03 0.011999 2.53 19.55 15.23 24.62 12.97 2.80 1.49 0.75 0.14 0.05 0.01 0.012000 10.47 6.56 29.00 11.20 11.36 5.70 1.10 0.57 0.31 0.07 0.02 0.01
CODIGFS index vs. VPA estimate of age group 6
97
96
95
9493
92
91
90
89
8887
86
85
R2 = 0.8513
0
20
40
60
80
100
120
0 20 40 60 80 100 120IGFS-Index
VP
A
0
200
400
600
800
1000
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002Year
Th
ou
s. t
on
ne
s
XSA TSA
EX-CAM AD-CAM
Coleraine ADAPT
BORMICON
COD COD Estimated 4+ biomass by different assessment models.Estimated 4+ biomass by different assessment models.
CODProbability plots of estimated fishable biomass in 2002-2005
0.0
0.2
0.4
0.6
0.8
1.02002 2003
0.0
0.2
0.4
0.6
0.8
1.0
600 800 1000 1200
2004
600 800 1000 1200
2005
1000 tonnes
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