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Demonstration of maternal effects of Atlantic cod: combining the use of unique mesocosm and novel molecular techniques

Contract nr: QLK5-CT-1999-01617
Project type: RS (Research and Technological Development Project)
Starting date: 01-01-2000
Duration: 36 months
Total cost: 1,589,578 EUR
EC Contribution: 1,057,102 EUR
Scientific Officer: Dominique LEVIEIL
Research topic: 5.1.2. Sustainable fisheries and aquaculture

Abstract:
Atlantic cod is a major target species for the European fishing fleet. All European cod stocks are under heavy fishing pressure or overexploited. An effect of are overexploitation is a reduction in the average age and size, with an increasing proportion of first-time spawners in the stock. The basis for this project is to follow offspring from selected families (pairs) of cod reared under identical and semi-natural conditions from hatching, through the larval and juvenile stages, and until sexual maturity, and compare their viability through these stages. Viability comparisons will be made between and within first-time (recruit) female spawners and elder (repeat) female spawners. The investigation will improve our understanding of the relative importance of individual genetic variation compared to maternal effects on growth and survival of cod, and the results will be incorporated into management models to study how to improve fishery management strategies.

Objectives:
The basis of this project is to follow offspring from selected families of cod reared under identical and semi-natural conditions from hatching, through the larval and juvenile stages, and until sexual maturity, and compare their viability through these stages. Comparisons of viability will be made between and within the two main experimental groups: first-time female spawners, and elder female spawners.

The main objectives are:

1.To examine the viability of offspring from first-time female spawners compared to offspring from elder female spawners of Atlantic cod.
2.To examine variations in viability between offspring of individual pairs of cod.
3.To analyse the demographic structure (age-, sex- and maturity structure) of selected European cod stocks by means of historical data sets.
4.Based on the results of objectives 1., 2. and 3., to evaluate the possible effects on cod recruitment and implications for fishery management.

The first two points will be examined by employing rearing experiments in large marine enclosures (mesocosms: 2,500 and 4,400 m3). The major viability measures are: growth, condition, and survival. These measures will be taken during the larval and juvenile stages, until sexual maturation. Fecundity and egg quality of each female will be related to viability. The parental identity of offspring will be ascertained using DNA microsatellite markers, which make it possible to link individual fish, sampled at any stage in their lifespan, to their parents. The influence of the male cod will be standardised by using elder males in both groups. The investigation will improve our understanding of the relative importance of individual genetic variation, compared to maternal effects (first-time vs. elder female spawners), on the growth and survival of cod in the wild and in aquaculture. If the maternal effect is important, this information will have significant implications for fishery management. We will examine the demographic structure of selected European cod stocks, in particular sexual differences in age, size and maturity in the spawning stock, by analysing data sets that extend back several decades in history. This information will be compared with our experimental results, to reveal how the composition of the spawning stock affects recruitment.

 


Coordinator
Terje SVAASAND
Institute of Marine Research
Bergen
NORWAY
Tel.: +47 55236891
Fax: +47 55236379
E-mail: terje.svaasand@imr.no


Partners
  Gary R. CARVALHO
The University of Hull
Hull
UNITED KINGDOM
Tel.: +44 1482 465540
Fax: +44 1482 465458
E-mail: g.r.carvalho@biosci.hull.ac.uk
  Dietrich SCHNACK
Institut für Meereskunde an der Universitaet Kiel
Kiel
GERMANY
Tel.: +49 43 15973910
Fax: +49 43 1565876
E-mail: dschnack@ifm.uni-kiel.de
  Helge PAULSEN
Danmarks Fiskeriundersogelser
Hirtshals
DENMARK
Tel.: +45 33963200
Fax: +45 33963260
E-mail: hep@dfu.min.dk