Exploitation-induced changes in farmed stocks Pacific oysters along the French Atlantic coast

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Commercial exploitation of living resources may have severe effects on populations and species. Firstly, changes in demographic properties such as population size and age and size structure may leave populations vulnerable to stochastic changes in environmental factors. Secondly, harvesting may induce changes in life history traits. Such changes may be expressed as either immediate plastic responses to environmental variation or adaptive evolutionary change due to changing fitness regimes (Stokes et al. 1993; Law 2000; Stokes and Law 2000; Heino and Godø 2002). During the last two decades, there has been an increasing interest for studying evolutionary changes in stocks of harvested marine species (Law & Grey 1989, Rijnsdorp 1993) and one major task is to separate environmental and evolutionary effects on observed phenotypic changes. Using a suitable model system, the Pacific oyster (Crassostrea gigas), we aim to disentangle plastic and evolutionary components of observed life-history changes in a farmed population.