Impact of juvenile Lake Sturgeon growth rate on sub-adult and adult recruitment in an impounded section of the Winnipeg River

Dwindling lake sturgeon (Acipenser fulvescens) populations indicate that research is needed to aid in developing conservation plans and restoration strategies. This study was conducted in an impounded section of the Winnipeg River, Manitoba, Canada, between Slave Falls and Seven Sisters Generating Stations. The upstream portion contains high densities of juveniles showing a slow growth rate, with the downstream areas containing lower densities growing at higher rates. Adults appear to favour the upstream half of the impoundment; however, sturgeon are less gregarious, with aggregations only occurring during the spring spawn and late fall. Interestingly, a long term netting program by resource managers suggests that adult numbers are relatively low. The high abundance of juveniles and low abundance of adults suggests that something is happening between the juvenile and adult phase in this population (“sub-adults”). Slow growth rates in the highly dense nursery areas may be limiting recruitment into the adult population. Alternately, adult recruitment may be limited by habitat and resources required by the adult phase. The general objective of this study was to address these uncertainties by focusing on the sub-adult phase and determine the fate of these fish once they leave the nursery areas and transition to reproductive adults.