Do North Sea cod (Gadus morhua) fisheries maintain high catch rates at low stock size?
Canadian Journal of Fisheries and Aquatic Sciences
This study presents an investigation of the relationship between stock size of North Sea 11 cod and catch rates in seven commercial fishing fleets. The shape of the relationship was estimated 12 using a new model allowing both density dependent changes in catchability and bias in the 13 assessment biomass estimates. Catchability in fisheries targeting a mixed species composition either 14 remained constant or decreased with decreasing stock size whereas catchability in targeted cod 15 fisheries
... ed cod 15 fisheries increased with decreasing stock size. However, even in the cases where catchability 16 increased, the change was insufficient to compensate for the decrease in stock size and catch rates 17 of all fleets decreased. Two factors which could lead to non-constant catchability were investigated: 18 the presence of a decoupling between stock size and density in high density areas, and the presence 19 of concurrent shifts in the spatial distribution of the cod stock and the cod fishery. No evidence of 20 the former was found but there was a northern shift in the spatial distribution of both effort and the 21 cod stock. 22 23