Category: Wildlife Research
Published: September 2004
Author(s): Jeffrey C. Lewis and Gerald E. Hayes
Fishers historically occurred throughout much of the low to mid-elevation forested areas of Washington, though they were not particularly abundant. The fisher was listed as Endangered in Washington in 1998 and is likely extirpated from the state. Two major factors contributed to the decline of fishers in Washington: over-exploitation via commercial trapping, and loss, degradation and fragmentation of suitable habitat. Poisoning and predator control, and incidental capture in traps set for other species were also considered contributing factors in the decline of fishers in the state. Despite protection from legal harvest since 1934, the fisher has not recovered. Extensive surveys from 1990 to 1997 failed to detect them. Reintroduction is considered the best way to recover fishers in Washington because of the absence of nearby populations to recolonize the state. Fishers have been successfully reintroduced in 10 states and 5 provinces in North America including Oregon, Montana, Idaho and British Columbia.
This study was undertaken by the Washington Department of Fish and Wildlife, in partnership with Northwest Ecosystem Alliance, to determine the feasibility of reintroducing fishers to Washington. A team comprised of scientists with expertise in fishers, carnivores, genetics and Geographic Information System habitat analysis provided guidance in design and implementation of the study. Objectives of the study were to determine if there was an adequate amount and configuration of fisher habitat and prey in Washington, if there was a suitable source population available for reintroduction, to assess potential interspecific impacts, determine implementation and legal requirements and to identify potential stakeholders and cooperators.
A habitat assessment was conducted to determine the amount and configuration of suitable fisher habitat in Washington and to evaluate its capability to support a fisher population. In the Pacific coastal states, fishers are closely-associated with late-successional forests; large trees, snags and logs are important resting and denning sites. Suitable habitat was defined as low elevation, late successional forest. The amount of late-successional forest needed to support a fisher population in Washington is unknown. The assessment was conducted for the Cascade Range and Olympic Peninsula based on the historical range of the fisher and the current distribution of late-successional forest.
Three potential reintroduction areas were identified from the habitat assessment: the Olympic Peninsula, Northwestern Cascades and Southwestern Cascades. The Olympic Peninsula had the largest amount of suitable fisher habitat; the largest amount of suitable habitat on public lands; the largest amount of suitable habitat in National Parks, National Monuments, and U.S. Forest Service wilderness areas; the largest land area with >50% suitable habitat; and the highest predicted carrying capacity of fishers. Within the Olympic Peninsula, the west side of the Olympic National Park was identified as the best location for a reintroduction. The Southwestern Cascades was the second best choice, and the Northwestern Cascades was ranked third.
In addition to current suitable habitat, results from forest growth modeling indicate that additional lateseral forest will become available within the next 80 years in concentrated areas on the Olympic Peninsula, particularly on the west side.
Late-successional forests support a greater richness and abundance of fisher prey species than secondgrowth forests. Potential reintroduction areas are landscape mosaics dominated by late-successional forests stands, and these are expected to provide a suitable prey base for a reintroduced population.
Genetic analyses indicate that fishers from British Columbia would be the most suitable source population for reintroductions in Washington. Fishers from California and Alberta would be the second and third most suitable source populations, respectively. Fishers are available from Alberta and may be available from British Columbia; however, they are not available from California due to small population size and protected status.
A fisher reintroduction in Washington is not likely to adversely affect recovery of state or federal species of concern. Although marten populations are suspected to be very low on the Olympic Peninsula and martens use similar habitats and prey species as the fisher, co-existence in other parts of their range suggests that fishers will not adversely affect marten populations. Because fishers are not protected under the Endangered Species Act, and there is no state forest practice critical habitat rule in Washington for this species, a reintroduction would not result in additional regulations for forest management practices on federal, state, or private lands, based on current statutes.
A number of cooperators and stakeholders are interested in a fisher reintroduction. Some have contributed to the assessment, including the Northwest Ecosystem Alliance, National Park Service, U.S. Forest Service and U.S. Fish and Wildlife Service. Other cooperators have offered support in implementing a reintroduction and include Northwest Trek Wildlife Park, Point Defiance Zoo, Woodland Park Zoo, and Oregon Zoo. Tribes, the Washington Department of Natural Resources, the Washington Trappers Association and Washington Forest Protection Association have been informed about the feasibility study and will be consulted with regarding a potential reintroduction.
The amount and configuration of suitable habitat, the availability of a suitable source population and the presence of a diverse prey base indicate that a fisher reintroduction is biologically feasible in Washington. National Park and National Forest lands on the west side of the Olympic Peninsula have been identified as the most suitable sites for a potential fisher reintroduction. It is recommended that a NEPA analysis be initiated for a proposed fisher reintroduction on the west side of the Olympic Peninsula on the Olympic National Park and Olympic National Forest.