Life history characteristics and distribution of lake sturgeon in an unfragmented section of a northern river

Lake sturgeon (Acipenser fulvescens), a potamodromous species, have been impacted by habitat fragmentation. Understanding the variation in population structure and spatial distribution in regulated and unimpeded rivers is valuable for recovery or rehabilitation purposes. The objectives of this study were to assess the relative abundance and spatial distribution of lake sturgeon in Rainy River and ascertain demographics of inhabitant juveniles. A standardized, index-netting study was conducted in the Rainy River to target juvenile and adult lake sturgeon. A total of 472 juvenile and 56 adult lake sturgeon were sampled. Juvenile and adult lake sturgeon were found throughout the river; however, juvenile relative abundance was greatest in the lowest river section close to the confluence with Lake of the Woods. Spatial clustering of juveniles and to lesser extent adults was also evident but adults were not necessarily segregated from juveniles. Juvenile annual survival rates were estimated to be approximately 75% and recruitment within this population was detected in all years but was variable in size. There were strong and weak year classes produced; however, they could not be explained by any of the environmental variables assessed.