Production, Predation and Food Niche Segregation in a Marine Shallow Soft-Bottom Community

A shallow soft bottom in Gullmar Fjord (Sweden) was investigated in order to determine the impact by epibenthic predators and possible competition for food between CO-occurring shrimp and fish species. Large numbers of the shrimp Crangon crangon, juvenile plaice Pleuronectesplatessa and sand goby Pornatoschistus rninutus aggregated during summer in shallow areas and fed on benthic macro-and meiofauna. Predation impact was calculated using estimates of gross production efficiencies and productlon rates. In 1976 and 1977, yearly predation amounted to 12 and 17 %, respectively, of the total macro-and meiofauna productlon. The low exploitation rate of the benthic community contradicts the hypothesis that predation should be the major extrinsic determinant keeping population levels below the carrying capacity of the environment. Shallow soft bottoms provide an abundant food supply that will neither limit growth nor produce severe competition between the epibenthic predators, although their diets are almost identical. It IS suggested that larger predators will control the abundance of epibenthic feeders such as shrimp, gobies and small flatfish inhabiting shallow water.