Trends In Biomass And Changes In Spatial Distribution Of Demersal Fish Species In Kattegatt And Skagerrak Between 1981-2003

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Overfishing and slow recovery of depleted fish stocks are currently a major global concern as they jeopardize the biological diversity of many marine ecosystems in major fishing areas. Accordingly, we analysed trends in biomass and changes in spatial distribution of 33 demersal fish species in a heavily exploited area, the Kattegatt and Skagerrak, between 1981 and 2003 using IBTS (International Bottom Trawl Survey) data. As in other exploited areas of the North Atlantic, the biomass, calculated as Catch Per Unit of Effort (CPUE), of round fishes (cod, pollack, hake and common ling) decreased drastically during this period possibly due to fishing pressure. However, other commercially important fish species (e.g. flat fishes) showed in this area a constant or increasing trend during the same period. Non-commercial species showed no or an increased trend in biomass (as much as 40 times in hagfish). Furthermore, a preliminary analysis of the spatial distribution of 12 selected fish species, explored by means of geostatistical methods and CV% (Coefficient of Variation), suggested a change in the degree of spatial aggregation as a function of the biomass.