A biologically-based movement model for plaice in the North Sea

In spite of increasing evidence of complex population structure and varying rates ofexchange of commercially exploited marine fish stocks between different management areas,the stock assessment methods currently used by ICES to advise on total allowable catches (TACs) and technical conservation measures still take only limited account of seasonal mi-grations and movements. As an example, plaice, Pleuronectes platessa L., is currently man-aged as a single stock in the North Sea. However a combined experimental approach usingconventional tagging data, and the release of hundreds of plaice tagged with electronic datastorage tags, have allowed the identification of population substructure and the characterisa-tion of annual migration routes and spawning areas. More recently, otolith microchemistryhas been used to determine the contribution of larvae from different spawning areas to dif-ferent nursery grounds, and the input from the nursery grounds to the adult population sub-units. Here a biologically-based population movement simulation model is presented whichutilizes data from each of these sources. The effects of a range of area and seasonal closureswere tested in terms of reduction in overall fishing mortality. Results from this study illus-trate the value of high-quality biological data to improve current advice on biologically andtechnically interacting fish stocks and fisheries.