FIELD-EVALUATION OF THE EFFECTS OF REFUGE USE AND CURRENT VELOCITY ONTHE GROWTH OF JUVENILE ICELAND SCALLOPS, CHLAMYS-ISLANDICA (MULLER,O.F., 1776)

We examined whether the use of crevices to avoid predators places Icel and scallops Chlamys islandica in flow conditions which result in redu ced growth. Field experiments in the Mingan Islands, northern Gulf of St. Lawrence, demonstrated that refuge use enhanced growth rates of sm all scallops (15-30 mm in shell height) but had no detectable effect f or larger individuals (30-60 mm). Thus, use of refuges does not appear to force scallops to trade-off survival and growth opportunities as g enerally assumed in predation risk theory. Current velocity, as estima ted from erosion rates of plaster blocks, was markedly less in refuges (approximate to 0.9 cm.s(-1)) than on exposed surfaces (approximate t o 1.9 cm.s(-1)). Feeding efficiency of scallops generally decreases wi th increasing current velocity. As the velocity threshold which inhibi ts filtration is generally lower for small individuals, the reduced cu rrent velocity could contribute to the higher growth of small individu als in crevices. (C) 1997 Elsevier Science B.V.