Effects of Winter Temperature and Predation on the Abundance of Alewife ( Alosa pseudoharengus) in the Bay of Quinte, Lake Ontario

Abstract

Alewife ( Alosa pseudoharengus) abundance in the Bay of Quinte, Lake Ontario, was monitored with a bottom trawl survey from 1972 to 1987. Prior to 1977, alewife catch-per-effort (CPE) was high in all areas of the bay but declined drastically following unusually cold winters in 1976–77 and 1977–78. Beginning in 1980, alewife CPE recovered in the lower bay, adjacent to Lake Ontario. This recovery was not observed in the upper bay where predation by a resurgent walleye ( Stizostedion vitreum) population maintained the reduced numbers of alewife. We conclude that walleye predation has played an important role in generating differences in alewife abundance between the upper and lower bays since 1980. There is a negative correlation between adult alewife CPE and young-of-year (YOY) alewife CPE suggesting that intraspecific predation is an important factor in the production of YOY alewife in the Bay of Quinte. Recruitment mechanisms for alewife in the Bay of Quinte may depend more on intraspecific predation, in contrast to Lake Ontario where intraspecific competition for zooplankton has been hypothesized as a limiting factor.