Effects of river flow on walleye (<i>Sander vitreus</i>) recruitment in the Saskatchewan River Delta

Alteration of natural flow regimes is affecting freshwater fish populations. For example, the walleye ( Sander vitreus) fishery in the Saskatchewan River Delta has declined since the mid-1990s, which may be related to changes to flow regimes due to upstream dams. To test this hypothesis, walleye age data obtained from otoliths collected through sustenance and commercial fishing were used in a generalized linear mixed model catch-curve analysis to test the relationship between discharge during predefined biologically significant periods and walleye recruitment. The best fit model identified that the fry growth period (weeks 30–42) had a positive relationship between river discharge and future recruits. Based on the estimated Bayesian posterior distribution, there was a very high probability ( p &gt; 0.99) that the effect was different from zero. This effect had an estimated 69% increase (28%–105% credible interval) in recruitment with every 100 m 3 ·s −1 increase in discharge over the fry growth period. These findings support previous work on walleye recruitment in another northern freshwater delta and will inform water resource management in these systems.