AUTHORS: Justin J. Remmers, Illinois Natural History Survey, Prairie Research Institute, University of Illinois Urbana-Champaign; Sarah Mayhew, Michigan Department of Natural Resources; Kirk Stodola, Illinois Natural History Survey, Prairie Research Institute, University of Illinois Urbana-Champaign; Maximilian L. Allen, Illinois Natural History Survey, Prairie Research Institute, University of Illinois Urbana-Champaign
ABSTRACT: Furbearer management plans often rely on population models to estimate the abundance and demographic trends of managed species. Fishers (Pekania pennanti), a medium-sized carnivore distributed across Canada and the northern United States, experienced population declines, extirpations, and range contractions in the early 1900s due to habitat loss, predator control, and overharvest by trappers. After being granted legal protections, fisher populations have expanded and recolonized parts of their historic range, enabling some states to allow limited harvest of the species. In particular, Michigan has had limited harvest of fishers in the Upper Peninsula for 30 years; however, the current abundance of fishers is unknown. To address this, we are developing a state-space model using age-at-harvest data to assess the current population status of fishers in Michigan’s Upper Peninsula (93,600 km2). We are investigating the influence of different sex- and age-specific life history traits (i.e., harvest season survival, non-harvest season, mean litter size) to determine how these traits affect the overall population size and where effort should be placed to increase precision of estimates. This work will be useful in predicting population changes and informing future harvest management of fishers. Based on preliminary analysis of current age-at-harvest data, juvenile fishers appear to be more susceptible to harvest and exhibit lower annual survival rates compared to adults. Given that female fishers undergo delayed implantation and will not give birth until their second year, high levels of juvenile and yearling harvest may be more impactful on fisher demographics, especially when compared to other furbearing species.
