Do observed levels of exploitation from consumption-oriented and trophy-oriented fisheries reduce relative stock densities of Muskellunge below target levels in northern Wisconsin?

Abstract

Muskellunge anglers desire to catch large fish, and release rates by recreational anglers often approach 100% (Isermann et al. 2011). Muskellunge are also a culturally significant fish for Chippewa tribes and support a subsistence spearing fishery in Wisconsin’s Ceded Territory (Erickson 2007). Although Muskellunge populations within the state’s Ceded Territory are exposed to both angling and spearing fishery exploitation, Faust and Hansen (2016) suggested that under certain conditions (e.g., high minimum length limits (MLL) and low spearing exploitation) Muskellunge fisheries with disparate motivations could coexist (i.e., sufficient numbers of large individuals remained despite harvest from consumptive fishery), but noted that larger declines in trophy Muskellunge abundance were predicted at lower MLLs (e.g., 102-cm). Fisheries managers with the Wisconsin Department of Natural Resources (WDNR) wished to further understand how specific relative stock densities (RSD), used by the WDNR to define and monitor trophy Muskellunge fisheries, are reduced at exploitation rates commonly experienced by populations in northern Wisconsin. Similarly, understanding how trophy Muskellunge abundance may have declined under the previous statewide MLL (i.e., 86-cm) at these levels of exploitation was also desired. Thus, our objectives were to 1) determine if observed levels of angling and spearing exploitation reduced predicted RSD indices below thresholds used by the WDNR to define trophy Muskellunge fisheries for three typical Muskellunge growth potentials in northern Wisconsin across a variety of MLLs; and 2) quantify how numbers of trophy Muskellunge declined under an 86-cm MLL at observed levels of exploitation.