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 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 nonstocked lakes to determine whether stocking enhanced muskellunge abundance. Density dependence of recruitment rates did not differe significantly between stocked and non stocked lakes but the recruitment rate was significantly higher in stocked lakes than in nonstocked 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 variable for muskellunge recruitment in Wiesoncin lakes. Adult stock density, stocked muskellunge density, average spring temperatures, 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.