GASTRIC EVACUATION IN LITTLE SKATE

The effects of prey type and prey preparation on the mathematical form s and rates describing gastric evacuation in little skate Raja erinace a were examined. Linear and square-root models best described the gast ric evacuation of whole, thin-shelled krill Meganyctiphanes norvegica, clam feet/muscle Spisula solidissimal/Placopecten magellanicus, polyc haetes Glycera spp. and sand lance Ammodytes dubius. Evacuation of kri ll and clams was faster than polychaetes and sand lance. A logistic mo del best described the evacuation data of thick-shelled benthic shrimp Crangon septemspinosa/Palaemonetes spp. Cut polychaetes Nereis spp, w ere digested at an exponential rate and were evacuated faster than wou ld be predicted based upon comparison with live polychaetes and previo usly published evacuation-temperature relationships. The results of th is study suggest that a single equation does not describe the evacuati on process for all prey, and that whole prey should be used if laborat ory-derived rates of gastric evacuation are to reflect what might occu r in wild fishes.