Trapping mortality accelerates the decline of the fisher, an endangered mesocarnivore, in British Columbia, Canada

Abstract

Understanding the environmental, demographic, and anthropogenic factors driving the population dynamics of endangered species is critical to effective conservation. Habitat loss, fragmentation, and trapping all have been linked to declines in the endangered population of fishersPekania pennantiin central British Columbia (BC), Canada, hereafter referred to as the Columbian population. Although the commercial trapping season for fishers has recently been closed in central BC, the animals are still taken in traps legally set for other furbearer species, and with this continuing source of mortality, the sustainability of this vulnerable population remains unclear. We constructed population viability models in the program Vortex to evaluate the specific impacts that trapping mortality would have on Columbian fisher population persistence under different trapping scenarios. Our modeling predicted that current mortality sources, including deaths in traps set for other species, will cause the population to disappear within 11 yr. When fur harvest mortality was removed from our modeling, the Columbian population appeared unlikely to persist beyond 37 yr. Our analysis provides evidence that along with the continued trapping closure for fishers in central BC, it is likely necessary to modify trapping regulations and methods (including restricting the use of kill traps) for other furbearers within Columbian fisher range to sufficiently reduce mortality from bycatch and help to avoid extirpation of the population in the near future. Additionally, identifying areas where fishers are actively breeding and protecting these habitats from further disturbances will be needed to increase survival and reproductive rates to levels high enough to reverse population declines over the longer term.