Environmental effects on recruitment of short-finned squid (Illex illecebrosus)

Abstract

Effects of variation in the ocean environment on abundance of northern short-finned squid (Illex illecebrosus) in the northwest Atlantic Ocean were investigated using a multiple regression model. A catch-based abundance index from two Canadian fishery areas was used as the dependent variable in time series analysis. Simple correlation analysis was used to select environmental indices. A model based on a 73-year time series of catch and meteorological data suggested that atmospheric forcing was related to squid abundance. Two other models were explored using a shorter (25-year) time series, which included an ocean temperature index and a Gulf Stream position index. One model utilized the catch-based index, whereas the other used a fishery-independent survey index as the dependent variable. All analyses indicated that squid abundance was positively related to a favourable oceanographic regime associated with a negative North Atlantic Oscillation (NAO) index (weak winter northwesterly winds), high water temperatures off Newfoundland and a southward shift in the position of the Gulf Stream and the boundary between the shelf waters and the offshore slope waters. In addition, increased meandering of the Gulf Stream appears to promote increased abundance, probably through enhanced shoreward transport of squid. Environmental relationships with squid indices are believed to reflect effects of broad-scale winter atmospheric circulation patterns on Gulf Stream dynamics, which largely regulate year-class strength of the dominant winter-spawning group early in life.