Food selection and consumption of the shrimp Crangon crangon in some shallow marine areas in western Sweden

Abstract

ABSTRACT: Crangon crangon L. is the dominant mobile epibenthic species in shallow waters of western Sweden. We report on seasonal food selection, die1 food intake, and quantify consumption of C. crangon in 4 different areas with different substrate and exposure. The main food item for small- sized C. crangon were rneiofauna, mainly ostracods and harpacticoids. Mid-sized and large shrimp preferred macrofauna such as Mya arenaria, Cardium edule, Nereis spp. and Corophium volutator. In some years also mobile epibenthos - such as Carcinus maenas, C. crangon and mysides - were eaten. Main feeding was during darkness with peaks around dawn and dusk. In summer an additional mid- day peak was found. Evacuation rate had a negative linear relationship with time; on average the food left the stomach within 2 h. Mean diel food intake in June and September was estimated to be 12.1 % of body wet weight. Total consumption during the ice-free period (April-December) was estimated to range between 3.7 and 14.8 g ash-free dry weight m-' in the 4 areas, giving a mean food conversion (P/C) of about 19 %. In one area, C. crangon annually consumed 10 to 121 % of the product~on of Nereis spp., 25 to 97 % of that of C. volutator, and 2 to 68 % of the combined production of the bivalves M. arenaria and C. edule. It can thus be concluded that C. crangon is one of the major benthos carnivores in these shallow areas and exerts a major impact on the infaunal comnlunity. INTRODUCTION