||Collie Jeremy, Rochet Marie-Joelle
||ICES Annual Science Conference, 20-24 Septembre 2010, Nantes
||The North Sea and Georges Bank fish communities have lost species and size diversity over the past several decades. Hypotheses that may explain these changes include climate change that may induce shifts in the food web, historical and contemporary fishing pressure and selective fishing of certain species or sizes. We use a comparative approach to examine the support for these different hypotheses. Using standardized trawl-survey data, we identify the useful indicators of species diversity, and functional diversity as measured by changes in size structure and changes in functional groups. The North Sea and Georges Bank fish communities have much in common, including shared species and congeneric species. However, the communities are subject to different fishing regimes and the North Sea has relatively less fish biomass in the larger size classes. We use a length-based multispecies model to investigate the role of fishing in causing and maintaining these differences in size distribution.