Climatic and hydrological determinants of year-class strength of St. Lawrence River lake sturgeon (Acipenser fulvescens)

Abstract

From 1991 to 1993, juvenile lake sturgeon (Acipenser fulvescens), mostly aged between 1 + and 12 + , were sampled with experimental gill nets in the St. Lawrence River and in two of its major tributaries (Des Prairies and l'Assomption rivers) to determine population age structure and year-class strength. A ratio of 1:7 was observed between the weakest (1980) and the strongest (1989) year-classes. Positive, significant correlations were observed between year-class strength and daily rate of increase in St. Lawrence River water temperatures in May and June, and mean June water flows in the Des Prairies River (the major spawning tributary in the system). The results suggest that year-class strength is determined in the first few months of life and that climatic and hydrological conditions in June, during which larvae drift from the spawning grounds and exogenous feeding begins, are critical determinants of year-class strength in St. Lawrence River lake sturgeon.