Objectives:

Describe changes in growth and maturity in various stock components over long time spans

Analyse reaction norms for age and size at maturation in various stock components

Compare to other Atlantic cod stocks

Advice to Management

Icelandic cod PhD studentGudrun Marteinsdottir – UniversityBjörn Steinarsson – MRI head of TAC groupGudmundur Thordarsson – MRI

Vilhjalmur Thorsteinsson – tagging MRIChris Pampolie/Anna Danielsdottir – genetics MRIKlara Jakobsdottir – genetics (PhD student)

External:Ulf Dieckman – Advice, PhD committeSkúli Skúlasson – Cod/Arctic charr collaboration

Icelandic cod - tasks

12 months: Database on biological data and on fishing effort on cod completed First analysis of changes in age and size at 50% maturity of cod completed

24 months: First analysis of probabilistic reaciton norms for age and size at maturation completed

36 months: Analysis of fishery-induced-changes in cod completed Probabilistic reaction norms for cod completed Analysis on the effects of climate and other environmental factors on maturation Comparative analysis on maturation in various stocks of Atl. Cod

48 months: All analysis and write-up completed and manuscripts submitted

Iceland - related projects

Historical changes in allelic frequency at 9 microsatellite loci among cod during 1948-2003 at two main spawning sites. Klara Jakobsdottir, PhD project within METACOD

Otolith growth of cod in relation to behaviour (deep vs shallow migration). Elvur Hardardottir MS project

Maturity of haddock: otolith growth and its influnce on maturation. Sólveig Einarsdóttir, MS project

Fishery induced changes among cod in Icelandic waters. Björn Steinarsson, Gudmundur Thordarsson and others. A new project at the MRI

Maturity and growth of wolffish. Asgeir Eiriksson MS project completed – to be continued

Spawning and fecundity of scallops –. Jónas Jónasson. A part of a PhD project

Icelandic cod - tasks12 months: Database on biological data and on fishing effort on cod

Database 1985-2004 ready (survey and samples from landed catch) – done

Database 1924-1980 ? (english data ?)

Fishing effort 1992-2004 – logbooksFishing effort 1930-1992 ? ---- CPUE data available – raw data ?

12 months: First analysis of changes in age and size at 50% maturity of cod done for survey data (1980-2004) for North and South

Paper 1: Changes in mean age at maturity based on historical series (1930 +) for as many components as possible (data limited)

Estimate historical F (do for spawning stock and feeding stocks if possible)

Attempt to estimate changes in maturity among smaller components that suffer from different fishing mortality

Age/size range of spawners / spawning areas (historical changes)

Environmental effects – look for abrupt changes (1984 onward) – reconstruct mat oogives.

Icelandic cod

Icelandic cod

Proportion of shallow, intermediate and deep types in early winter migrations

0%

25%

50%

75%

100%

area11 area31 area32 area33 area34 Total

Locality of release (spawning grounds)

Shallow

interm.

Deep

Vilhjalmur Thorsteinsson, in prep

Variability in exploitation rates between spawning grounds

Spawning ground 1, ID 3.1.Near shore, shallow water 50 m 1996 release N=1042, Total recaptures 302 or 29 %Z + X = 1.2

Spawning ground 2, ID 3.4.Off shore, 100 m depth 1996 release N=574 Total recaptures 89 or 15 %Z + X = 0,6

0

1

2

3

4

5

6

1 2 3 4

a31-1995

a34-1995

Linear (a31-1995)Linear (a34-1995)

1) Z + X = 1.2

2) Z + X = 0.6

Time in years

Nlo

g r

ecap

ture

s /

year

Vilhjalmur Thorsteinsson, in prep

Icelandic cod - tasks

24 months: First analysis of probabilistic reaction norms for age and size at maturation completed

Paper 2:

Data: Survey data 1985-2004

Archived data back to 1930 ?

Method: Start with cohorts 1985-2004

Do males and females separately

Distinguish between first time and repeat spawners ?

Do for earlier years (DNA otolith results indicate changes during 1950-1965)

Difficult (data problems) !!!! – do other species

Icelandic cod - tasks

36 months: • Analysis of fishery-induced-changes in cod completed• Probabilistic reaction norms for cod complete• Analysis on the effects of climate and other environmental factors on maturation

– done for growth (?)• Comparative analysis on maturation in various stocks of Atl. Cod

Environment: A part of a larger MRI projectRecent (1973+) changes in effort and physical and biological parametersTemp, salinity, capelin, shrimp

Student: create long term indices based on historical weather readings andglobal environmental indices (jointly with other projects on cod recruitment) – use in reaction norm analysis

Do other species ?

Paper 3: Modelling - explore the role of stock structure and behavioural variation in maintaining sufficient (?) genotypic and phenotypic variation within the stock even though parts of the stocks have been exposed to high fishing pressures.