Forestry, fire and fur: Factors driving the decline of fishers (Pekania pennanti) in Central Interior British Columbia

Understanding the factors driving the population dynamics of endangered species is critical to effective conservation. Demographic information on how environmental and anthropogenic influences affect a species distribution and abundance provides valuable information to wildlife managers looking to accurately assign conservation status, deploy limited resources efficiently, and set sustainable harvest levels. Unfortunately, obtaining detailed population data for rare and cryptic species that naturally occur at low densities is challenging, and in many cases not enough is known to develop appropriate conservation measures. One such species is the fisher (Pekania pennanti), a mid-sized mustelid considered a species-at-risk over much of its North American range. Using a combination of DNA-based mark-recapture surveys and population viability analysis (PVA), I evaluated the factors driving the declines being seen in the geographically isolated and endangered Columbian population of fishers (Pekania pennanti) in central interior British Columbia (BC), Canada. I estimated the density and abundance of fishers in two spatially distinct ecosystems in central interior BC where current data were lacking, and assessed which ecological and anthropogenic factors best explained the distribution of fishers in each ecosystem. Additionally, I constructed population viability models to assess the specific impacts that trapping mortality would have on the persistence of the Columbian population of fishers under different trapping scenarios. I found the density of fishers in my two study areas varied substantially, primarily due to the level of trapping mortality occurring during each survey season. The density of fishers in the Chilcotin study area west of Williams Lake was among the highest ever reported for the province (~21 fishers/1000 km2), whereas density in the Enterprise study area south and east of Williams Lake was among the lowest (~9 fishers/1000 km2 ). Habitat covariates that best explained the density of fishers were similar between both study areas; forested stands with wet soil moisture regimes composed of older deciduous and spruce trees were most strongly related to higher densities in both the Chilcotin and Enterprise study areas. My population modelling suggests that if current mortality rates continue, including deaths from trapping, the Columbian population of fishers will likely be extirpated from central interior BC within two decades. In the absence of additional fur harvest mortality, the Columbian population appeared unlikely to persist beyond 37 years without additional measures being taken to increase female survival and reproductive output. This study provides valuable information to wildlife managers looking to allocate limited resources to aid in the recovery of an isolated and endangered species in central interior BC. Conservation priorities for the Columbian population of fishers should focus on eliminating mortality from trapping, and protecting the high-value habitats the species requires to survive and reproduce.