Detection of natural barriers to movement of lake sturgeon (Acipenser fulvescens) within the Namakan River, Ontario

Many populations of lake sturgeon (Acipenser fulvescens Rafinesque, 1817) are below historic population sizes, and migration barriers have likely contributed to some of these population declines. Dams and natural barriers can potentially isolate populations along a single river and can have a strong effect on the ability of lake sturgeon to move upstream. Along the Namakan River in Ontario, Canada, a series of natural rapids could impede movement of lake sturgeon and fragment the sturgeon into several small populations. Movement patterns of lake sturgeon were assessed using genetics and acoustic telemetry. Samples were collected from five locations along the river, each one separated by a rapid or falls, and were analyzed at 12 microsatellite loci. No significant genetic differences were observed between the five segments, indicating that the groups of lake sturgeon are not isolated. There were no significant differences in genetic diversity between the five segments. Therefore, migration is likely occurring both upstream and downstream. The acoustic telemetry study also confirmed bidirectional movement of adult fish. The natural rapids and falls along the Namakan River do not appear to be a significant barrier to movement of lake sturgeon, and the lake sturgeon within this river represent a single population.