Historical harvest and incidental capture of fishers in California

Abstract

Recent petitions to list the fisher (Martes pennanti) under the Endangered Species Act have brought attention to fisher conservation. Although commercial trapping of fishers in California ended in 1946, summarizing the commercial harvest data can provide a historical perspective to fisher conservation and may indicate the prevalence of incidental fisher captures in traps set for other species. We investigated the relationships between historical fisher harvests and the price paid for fisher pelts, number of trapping licenses sold, cost of a trapping license, total number of 5 sympatric species harvested, and their pelt prices in California. The frequency of incidental captures was also assessed by interviewing trappers, biologists, and wardens in California. Between 1919-1946, relatively few fishers were legally trapped in California (n=462, x=18.5 annually), and their harvest declined steadily. Fisher harvests were positively related to fisher pelt price but were more strongly related to the number of trapping licenses sold, indicating that fishers were vulnerable to trappers in general as opposed to only those trappers specifically targeting them. We estimated an incidental capture rate of 1 per 407 set-nights and a mortality-injury rate of 24% from data obtained from 5 trappers in California. Trappers are an important source of information on the distribution of fishers and their cooperation is necessary to determine the effects of incidental capture on fisher populations.

Citation

Lewis, Jeffrey C.; Zielinski, William J. 1996. Historical harvest and incidental capture of fishers in California. Northwest Science 70(4):291-297