Seasonal abundance and vertical distribution of capelin (Mallotus villosus) in relation to water temperature at a coastal site off eastern Newfoundland

Abstract

The seasonal abundance and vertical distribution of capelin in relation to water temperature have been investigated by conducting repeated hydroacoustic surveys at a coastal site off eastern Newfoundland. Water temperatures were warmer in 1983 than in 1984 as indicated by the earlier appearance and greater depth of the seasonal thermocline. Correspondingly, schools of capelin appeared earlier, were more abundant, and extended deeper in the water column in 1983 than in 1984. Most capelin were found between the surface and the 5C isotherm. In both years, initial peaks of capelin abundance occurred when nearshore water temperatures increased from about 0-1 C to above 6C and, at or near, periods of maximum tidal oscillation. Short-term variations in the depth of the 5C isotherm were related to nearshore wind-induced upwelling events. Annual variations corresponded to the volume of cold (<0C) water and sea-ice transported south by the Labrador Current.