Juvenile lake sturgeon monitoring and determinants of year-class strength in the Rupert River, mid-northern Québec, Canada

Abstract

In 2007, Hydro-Québec began the construction of the Rupert Diversion in conjunction with the Eastmain-1A and Sarcelle powerhouses. The partial diversion of the Rupert River became operational in 2009. Mitigation measures to preserve lake sturgeon (Acipenser fulvescens) habitat downstream of the diversion include an instream flow, weir and spurs to maintain water levels, and fish passage channels and spawning grounds. An environmental follow-up was done in the reduced-flow section of the Rupert. The baseline status was established from 2007 to 2009 and follow-up studies were conducted from 2010 through 2012, and in 2014 and 2016. Besides presenting results from Hydro-Québec's environmental monitoring, analyses were performed to search for determinants of year-class strength. The results of the lake sturgeon monitoring activities indicate that the abundance of juveniles ≤8-year-old in the reduced flow section of the river remained similar or increased. Although larval production increased in post diversion conditions, cohort strength tended to decrease as did juvenile growth. Year-class strength was positively correlated with spring and summer flow. Also, a significant, strong negative correlation was found between estimated larval abundance and water temperature during larval drift.