Migratory behaviour, seasonal activity and condition levels in lake sturgeon in the vicinity of a hydroelectric facility

Three performance based activities of lake sturgeon (Acipenser fulvescens) were examined. These included: (a) examining migratory behaviour and seasonal reproductive development patterns, (b) measuring locomotory activity, and associated metabolic costs, of lake sturgeon in the field and (c) determining the potential influence of a hydroelectric facility on the mobilization of plasma nonesterified fatty acids in lake sturgeon. Each study was conducted on the Mattagami River in northeastern Ontario. Radio tracking and systematic sampling of lake sturgeon within the study area revealed an annual pattern of migration. The initial upstream migration of mature fish began in January and ended with fish at spawning sites by May. Following a short spawning period, individuals dispersed downstream during May and June. A second upstream migration to an overwintering area began in mid-summer. A marked decline in gonadosomatic index (GSI) and plasma levels of sex steroids between early and late May was consistent with a short spawning period. Measurement of GSI and circulating sex steroid levels in both sexes indicated a divergent pattern of ovarian and testicular development in lake sturgeon. In males, gonadal recrudescence began within one month of spawning and was at prespawning levels by September. In females, resumption of ovarian development was not evident until September.;Use of plasma nonesterified fatty acid (NEFA) levels as a direct measure of nutritional condition revealed that lake sturgeon collected upstream of the hydroelectric facilities mobilized significantly higher levels of NEFA than individuals collected downstream in the spring. Further analysis of the individual fatty acid species indicated that sturgeon located downstream of the facilities mobilized fatty acids which are typically retained by other fish species (i.e. 22:6n3), even when starved. The significantly higher 22:6n3 levels below the generating stations may indicate a more restricted intake of n3 fatty acids and/or an extreme metabolic condition requiring the mobilization and oxidation of all fatty acids.;Laboratory experiments, designed to calibrate a bio-sensitive radio transmitter to swimming speed, indicated that aerobic electromyograms could be correlated to swimming speed and oxygen consumption. Measurement of locomotory activity in the field revealed that lake sturgeon are more active during the fall than the summer. During the summer, lake sturgeon utilize less than 50% of their metabolic scope whereas in the fall they apparently utilize the entire metabolic scope. High activity was also evident during the winter.