Effect of stocking and biotic and abiotic factors on Muskellunge recruitment in northern Wisconsin lakes
The Muskellunge Esox masquinongy is an important recreational fish species in North America. Some populations of Muskellunge are in decline, despite a reduction in harvest by anglers due largely to a growing catch-and-release ethic. Our objectives were to determine if Muskellunge recruitment was influenced by stocking, biotic factors, and abiotic factors in northern Wisconsin lakes. To address our first objective, we compared parameters of Ricker stock-recruit models from stocked and non-stocked lakes to determine whether stocking enhanced Muskellunge abundance. Density dependence of recruitment rates did not differ significantly between stocked and non-stocked lakes, but the recruitment rate was significantly higher in stocked lakes than in non-stocked lakes. This finding confirmed that Muskellunge stocking significantly increased recruitment in Wisconsin lakes, so stocking can continue to be used to supplement Muskellunge populations with low natural recruitment. To address our second objective, we tested biotic and abiotic variables in stock-recruit models as possible explanatory variables for Muskellunge recruitment in Wisconsin lakes. Adult stock density, stocked Muskellunge density, average spring temperature, spring temperature variation, and age-0 Walleye Sander vitreus abundance explained significant Muskellunge recruitment variation. Our findings indicate that Muskellunge recruitment is regulated by a mix of stocking, as well as abiotic and biotic environmental factors in northern Wisconsin lakes.