Age-Structured Assessment of Walleyes, Saugers, and Naturally Produced Hybrids in Three Missouri River Reservoirs

Walleye Sander vitreus and sauger Sander canadensis naturally hybridize in many populations, but the factors influencing the recruitment of hybrids are unknown. We determined relative year-class strength for 1,454 saugers, walleyes, and naturally produced hybrids from three Missouri River reservoirs. Hybridization rates varied from 4% in Lakes Sharpe and Francis Case to 21% in Lewis and Clark Lake. Hybrids comprised multiple year-classes in each system, indicating that hybridization does not occur in erratic pulses but at a consistent low-level recruitment rate. The year-class strength of hybrids was not correlated with that of either walleyes or saugers. Our models suggest that higher than average recruitment of walleyes, saugers, and hybrids can be expected during years with warmer spring and early summer water temperatures in Lake Sharpe and Lewis and Clark Lake and during years when inflow (from main-stem discharge for hybrids and tributary inputs for saugers and walleyes) is reduced in Lewis and Clark Lake.