THE ROLE OF SUB-STOCK STRUCTURE
IN THE MAINTAINANCE OF COD METAPOPULATIONS


North Atlantic cod stocks appear to be overexploited and in a depleted state. A recurrent feature of the declines in abundance, has been collapse of the spatial distributions of fish and loss of the distinct sub-stocks. There is evidence that a diverse sub-stock structure is necessary to ensure the long term health and productivity of fish stocks, but maintaining this is not recognised as an objective of current fisheries management. The overall objective of this project is to develop the conceptual and mathematical basis for advising on how fisheries management measures might be framed to conserve or restore not only stock biomass, but also sub-stock diversity. We shall accomplish this by studying, and developing models based on, the cod stocks off Iceland and the west and north of Scotland. The aim will be to establish the extent of genetic sub-structure in these stocks, how it is maintained, and the extent to which overall population dynamics are dependent on the sub-stocks.