Response of capelin to wind-induced thermal events in the southern Labrador Current

Abstract

The response of schooling fish (Capelin Mallotus villosus Müller) to coastal upwelling events in the southern Labrador Current was investigated during the summer of 1984 and 1987. Theoretical calculations showed that summer wind events, which prevail from the southwest, were capable of inducing upwelling along the western boundary of the Avalon Channel. Significant drops in the temperature of subsurface water near the coast occurred in response to longshore wind stress. Coherence of longshore winds and thermal fluctuations was significantly greater than zero at periods between 3.8 to 6.1 days at two exposed locations along the coast. Regression of temperature on longshore winds was significant when effects of cross-shore winds were removed by regression. Regression of temperature on cross-shore winds was not significant when effects of longshore winds were removed by regression. During 1984 the relative catch rate of male capelin at a trap increased when water temperature rose rapidly after upwelling events. During 1987 increases in the catch rate of males at the trap were correctly predicted from cessation of upwelling favorable winds (i.e., from the south). Shoreward movement of capelin after wind driven upwelling may synchronize spawning with periods of light wave action on beaches in eastern Newfoundland