SIMULATED CARRYING CAPACITIES OF FISH IN NORWEGIAN FJORDS

The influence of oceanographic and meteorological conditions and topog raphy on the carrying capacity of organisms in coastal areas of wester n Norway is investigated by field studies and dynamic modelling. Publi shed data on Calanus finmarchicus, the dominant species in the zooplan kton biomass of west Norwegian coastal waters, demonstrate a strong gr adient, with high densities at the outer coastal areas and lower densi ties at the innermost localities. This gradient spans several orders o f magnitude. A similar tendency is found in the data from pelagic traw ling and from beach seine catches, and simulation modelling indicates that fish production depends on zooplankton availability. According to the model, the carrying capacity lever of fish production is high in the outer areas and decreases with distance from the outer coast accor ding to the decrease in advected biomass of zooplankton. The simulatio ns indicate that while growth prospects for individuals at lower troph ic levels vary with the distance from the coast, potential for growth seems largely unaffected by the distance from the coast for the sublit toral piscivores (e.g. cod). This indicates that, for immigration of a new sublittoral piscivore to a habitat, it does not matter whether th e habitat is situated close to the outer coast or far from it. A conse quence for stock enhancement may be that a small-scale release of subl ittoral piscivores will be equally productive in most coastal areas, w hile the outcome of a large-scale release will be strongly dependent o n distances from the coast. The outcome may be high, but variable, in the outer areas and low, but probably more constant in the innermost a reas, provided that releases of juvenile, sublittoral, piscivorous fis h do not result in a fish stock density in excess of the carrying capa city level.