Environmental flows and recruitment of walleye (Sander vitreus) in the Peace-Athabasca Delta

Age composition data from a commercial walleye (Sander vitreus) fishery in the Peace-Athabasca Delta were used to test the hypotheses that recruitment varied interannually and that recruitment was related to local hydrological conditions. Variable interannual recruitment was strongly supported over a null model of constant annual recruitment. Assuming recruitment strength was established in a walleye's first year of life, several a priori hypotheses relating recruitment to river discharge or lake levels were tested using an information-theoretic approach. The data best supported the hypothesis of a positive relationship between walleye recruitment and mean discharge in the Athabasca River during the fry rearing period (weeks 18-43). Approximately 25% of observed variability in annual recruitment could be explained by mean discharge during the fry period. However, the data could not fully rule out the alternate hypotheses that recruitment was related to mean discharge in the Athabasca River over the entire year or during winter. Several mechanisms are hypothesized to explain the positive relationship, including increased space in preferred open-water habitat or greater food production from nutrient inputs or wetted area. The observed correlation between river discharge and walleye recruitment can be used to help us understand water management planning on the Athabasca River.