TEMPERATURE EFFECTS ON PREDATION OF JUVENILE SEA SCALLOPS [PLACOPECTEN-MAGELLANICUS (GMELIN)] BY SEA STARS (ASTERIAS-VULGARIS VERRILL) AND CRABS (CANCER-IRRORATUS SAY)

Predation of juvenile sea scallops Placopecten magellanicus by sea sta rs Asterias vulgaris (80-100 mm diameter) and crabs Cancer irroratus ( 80-98 mm carapace width) was examined in the laboratory at different s eawater temperatures. Prey sizes used were those demonstrated previous ly to be preferentially consumed by the respective predators. Consumpt ion rate of small (5-9 mm shell height, SH) scallops by sea stars was not significantly different at 40 and 8 degrees C, but was significant ly higher at 15 (d)egrees C (Q(10) = 6.9). Similarly, consumption rate of large (19-23 mm SH) scallops by crabs was not significantly differ ent at 3 degrees and 8 degrees C, but was significantly higher at 15 d egrees C (Q(10) = 2.1) Increased predator activity, as indicated by in creased time spent searching for prey, increased predator searching mo vement velocities (which, for sea stars, resulted in increased encount er rates with scallops), and shorter prey handling times, explained pa rt of the increased predation rate by sea stars and most of that by cr abs. Predation fate by sea stars also increased with temperature becau se of decreased effectiveness of the scallops' escape response, as evi denced by a significantly higher probability of capture upon encounter at 15 degrees C than at 4 degrees and 8 degrees C, although the proba bility of sea stars capturing scallops was very low (< 0.1) at all exp erimental temperatures. The probability of crabs capturing encountered scallops was higher (> 0.3) and independent of temperature. The proba bility of sea stars and crabs consuming captured scallops was similar to 1 and temperature independent.