BEHAVIOR AND ENERGETICS OF WHELKS, BUCCINUM-UNDATUM (L), FEEDING ON ANIMALS KILLED BY BEAM TRAWLING

Whelks, Buccinum undatum, are potentially important scavengers of anim als damaged or killed as a result of beam trawling. In order to assess the ability of whelks to scavenge these moribund animals, and the con sequences of this to energy flow, we presented them with four differen t species that were either damaged on the seabed or died as a result o f capture by beam trawling. Whelks ate swimming crabs, Liocarcinus dep urator, purple heart urchins, Spatangus purpureus, and a gadoid fish, the pouting, Trisopterus minutus, but not plaice, Pleuronectes platess a. Whelks moved most rapidly towards swimming crabs, suggesting that t hese were the most preferred prey type. Although the rate of energy in take was highest when whelks fed on sea urchins, when fed to satiation they acquired most energy from swimming crabs, When presented with wh ole animals, whelks fed preferentially on different body tissues, e.g. they consumed the eyes of pouting first, and never ate the gills or c arapace of swimming crabs. Absorption efficiency was highest when fed a diet of swimming crabs (93%)and lowest when fed pouting (83%). Whelk s are able to efficiently utilise animals killed by beam trawling, and our results indicate that they prefer the most energetically rich spe cies. In areas of intense beam trawling, such as the southern North Se a, dead or moribund animals which result from these activities could c onstitute a considerable proportion of whelk diets.