Jóhann Sigurjónsson (1.081Mb)

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Cod in Icelandic waters: Biology, exploitation and management

Jóhann Sigurjónsson

Marine Research Institute, Reykjavik 10th Norwegian-Russian Symposium on

Management strategies for commercial marine species in northern ecosystems,

Bergen, 27-29 August 2003

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Temperature Deviations at Siglunes North Iceland (50m depth)

1950-2003

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Ár -3

-2 -1 0 1 2 3

Hi ta fráv ik m iðað v ið 1. júní , ° C

Warm 1920-64

Ice years

Warm/Cold

Warm again ?

°C

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Symposium, Bergen , 27-29 August 2003 J. Sigurjónsson - Mar. Res. Inst., Iceland 3

OCEAN CURRENTS

Gulf-Stream (warm)

E-Greenland Current

(cold) E-Iceland Current

(cold)

ICELAND

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Main spawning areas and feeding migrations

Iceland Cod

Spawning

Feeding

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0.87

0.74

0.99 0.63

(Begg and Marteinsdóttir, 2000)

0.97

Larval drift from SW Iceland clockwise 1970-1998

Iceland Cod

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0 25 50 75 100

9 10 11 12 13 14 15 16 17 18 19 20

0 25 50 75 100

9 10 11 12 13 14 15 16 17 18 19 20 1994

1995 1996 1997 1998

MARCH APRÍL MAY

0 25 50 75 100

9 10 11 12 13 14 15 16 17 18 19 20

Weeks (9-20)

Females 70 - 100cm Females

> 100cm

Females

< 70 cm

%Females spawning

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Aldur lirfa í dögum

% lirfa m. fæðu í maga

0 20 40 60 80 100

1 2 3 4 5 6 7 8 9 10 11

Egg diameters > 1.5 mm Egg diameters 1.35 - 1.5 mm Egg diameters < 1.35 mm

Cod larvae from large egg are bigger, start feeding early, have faster growth, and have higher survival than juveniles from

small eggs

Cod Spawning

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Mean length (cm) of 4 year old Cod

< 35 35 - 40 40 - 45 45 - 50 50 - 55 55 - 60 60 - 65

> 65

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Iceland Cod: Maturity at age in bottom trawl survey in 1985-2003

0 20 40 60 80 100 120

1985 1987 1989 1991 1993 1995 1997 1999 2001 2003

% m a tu ri ty

^{age 4}

age 5 age 6 age 7 age 8 age 9

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Iceland Cod: Average food composition

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0 500 1000 1500 2000 2500

78 80 82 84 86 88 90 92 94 96 98 Year

Thous.

tons

2,8 3,0 3,2 3,4 3,6 3,8 4,0 4,2 4,4 Mean wt

6 yr old cod

CAPELIN STOCK SIZE AND WEIGHT OF

COD THE FOLLOWING YEAR

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Components of advice (short-term)

Data Data analysis Assess. Prediction

Landings Length

meas.

Otoliths

Surveys

Catch in numbers

Indices

Stock assessment

Predicted developm.

of stock and catch Logbooks

CPUE

Otoliths

Length m.

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Standardised Groundfish Survey (Spring)

- Independent estimate of relative abundance - Annual indices of recruitment

- Various biological parameters

- 600 stations - Since 1985

- Also autumn survey, Spawning

survey

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Cod fishery off Iceland 1905-2000

0 100 200 300 400 500 600

1905 1925 1945Year 1965 1985

Aðrir

Íslendingar

Catch thous. tons

Iceland

Others

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Iceland Cod: Landed catch (thous.

tons) by age 1928-1999

0 100 200 300 400 500 600

28 33 38 43 48 53 58 63 68 73 78 83 88 93 98 Year

La nde d c a tc h t hous . t ons

+12 yrs 9-11 yrs 6-8 yrs 3-5 yrs

12+ yrs 9-11 yrs

6-8 ára

3-5 yrs

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Iceland Cod: Landings by fishing gear

0 20 40 60 80 100

Bottom trawl

Gillnet Longline Handline Danish seine

%

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Cod management considerations

 Not beneficial to catch fish at young age - let it grow older

 Apparently low mortality in old fish

 Stock/Recruitment relationship - significant despite variability

 Large females very important for successful

spawning

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Weight increase in cod by age

3-4 4-5 5-6 6-7 7-8 8-9

Age in years

W ei ght i nc reas e (% ) ⁸⁰

60

40

20

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Number of fish in catch: Year class 1922 caught at low F and 1983 at high F

No s ( m ill. f is h )- log s c al e

5 10 15

0.001 0.100 10.000

1922

1983

Age 1

0.1

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Spawning stock biomass and deviation from mean recruitment of 3yr old cod

0 200 400 600 800 1000 1200 1400

1955 60 65 70 75 80 85 90 95 2000

S pa w ning s toc k

-200 -100 0 100 200 300 400 500

R e c ruit m e nt ( m ill)

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Other management measures

 TAC with ITQ’s for vessels

 Temporary closures of areas with by-catch of juveniles

 Permanent closures of small fish areas

 Temporary closures of spawning grounds

 Fishing gear area restrictions

 Mesh sizes in trawl 155mm

 Mesh size in gillnets not exceeding 8”

 Sorting grids for juvenile and small cod to

escape

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Harvest Control Law (HCL): Assumed future catch of cod off Iceland if 25% of fishable

biomass is taken

0 100 200 300 400 500

1993 1996 1999 2002 2005 2008 2011 2014 2017 2020

Thous. tons Risk Analysis

95%

5%

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Cod: Proportion harvested (%) of fishable biomass

0 10 20 30 40 50

1980 1985 1990 1995 2000

%

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Cod recruitment: 1960-2002 year classes at 3 years of age

0 100 200 300 400 500

1 96 0 6 5 7 0 7 5 8 0 8 5 9 0 9 5 2 00 0

Year class Millj.

fish

Estimated Greenland migration

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COD: History of stock size and likely development according to HCL

0 300 600 900 1200 1500

1980 1985 1990 1995 2000

Year Th.

tons

Fish.stock Spawning stock

HCL

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Conclusion

 HCL has improved setting of adviceable TAC

 There are reasons for slow recovery of stock

– Slight but steady overharvest, catch exceeding advice

– Changed climatic regime

– Changed exploitation of marine life

– Increased whale stocks ? Damaged habitat ?

– Overestimation of stock size

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