Food selection and consumption of mobile epibenthic fauna in shallow marine areas

Abstract

Food selection and consumption of the dominant species among mobile epibenthic fauna was investigated in shallow waters on the Swedish west coast. Newly recruited Pomatoschistus rnicrops, P. minutus, Pleuronectes platessa and Crangon crangon fed initially on meiofauna, whereas young stages of Carcinus maenas preferred 'detritus' (including plant material) and juvenile specimens of macrofauna. Older stages of all 5 species fed on macrofauna. In 1 yr (197?), when low recruitment of some usually abundant macrofaunal species occurred The mobile epibenthic predators are considered opportunistic carnivores mainly feeding on infauna which they select on the basis of relative availability. Total annual food consumption of mobile epibenthic fauna in one area, Gullmarsvik 1978, was calculated to be 26 g AFDW m-2. Food conversion ( P C ) was estimated to be about 0.2 for crustaceans and 0.3 for fishes. The mobile epibenthic fauna consumed 60 to 98 % of the production of the dominant infauna: harpacticoid, ostracods, Corophium volutator, Mya arenaria and Cardjum edule, and is considered as the major biotic regulator of the infauna. In general, food-niche overlap decreased with increasing difference in size between 2 predator species. C. volutator was preferred by all epibenthic predators during most seasons and in Gullmarsvik 1978 contributed on average about 60 % of the food overlap between pairs of predators. M. arenaria and C. edule together made up about 70 % of the food overlap in July and August in this year, and the mobile epibenthic fauna consumed 98, 62 and 92 % of the production of C. volutator, M. arenaria and C. edule, respectively. This strongly suggests that competition between predators exists for these infaunal species, at least during parts of the season.