Cascades fisher reintroduction project: Final project report

Lewis, Jeffrey; Ransom, Jason; Chestnut, Tara; Werntz, David; Black, Sandie; Whiteside, Douglas; Postigo, Jose; Moehrenschlager, Axel

doi:10.36967/2293605

Fishers (Pekania pennanti) are a mid-sized member of the weasel family that historically occurred in the dense coniferous forests of Washington. Unregulated harvest, loss and fragmentation of habitat, and predator control campaigns beginning in the late 1800s collectively resulted in the decline and extirpation of fishers from Washington by the mid-1900s. Fishers were subsequently listed as an endangered species by the state. We established a partnership between federal, state, and non-profit organizations with the goal of re-establishing self-sustaining fisher populations in their former range in Washington, which includes the Cascade Range. Our objectives were to 1) Release ≥80 fishers into the South Cascade Ecosystem and ≥80 fishers into the North Cascades Ecosystem, with ≥50% female composition, 2) Release fishers at few locations in each reintroduction area to increase the likelihood of fishers interacting, 3) Release as many fishers as possible before January 1st each season, so that the stress of the reintroduction process occurred well before the active gestation period of female fishers, and 4) Monitor post-release movements, survival, home range establishment, and reproduction to evaluate initial success of the reintroduction project during the two years following their release. From 2015–2020, we translocated 81 fishers (69 fishers (38 F, 31 M) from British Columbia, Canada, and 12 fishers (7 F, 5 M) from Alberta, Canada) into the South Cascades, including Mount Rainier National Park, and Gifford Pinchot National Forest. From 2018–2020, we translocated 89 fishers (48 F, 41 M) from Alberta, Canada, into the North Cascades, including North Cascades National Park Service Complex and Mount Baker-Snoqualmie National Forest. We monitored fishers using radio-telemetry from 2015–2021, and collected 1,298 fisher locations during those efforts. We supplemented those data with incidental verified detections captured on remote trail cameras during the same time period, which totaled an additional 277 locations. Collectively, these detections ranged across 18,573 km2 of the South Cascades and 15,452 km2 of the North Cascades. The project was a successful conservation action: we achieved our stated objectives and met most benchmarks of success for reintroduction and animal welfare. We were able to translocate 170 fishers from Canada to the Washington Cascades that met all optimal health criteria and represented a young founder population with a slightly female-biased sex ratio. We moved fishers efficiently, reduced their time in captivity throughout the project, and met high standards of animal care and welfare. We released fishers at a few centralized locations in each portion of the recovery area, hopefully facilitating interaction and reducing the tendency for animals to wander far in search of conspecifics. We also released most fishers before January 1 of each year, which allowed animals to settle and begin establishing a home range before the onset of breeding season. Reproduction was documented in both the North and South Cascades within two years of release, with one female in the North Cascades producing a litter of 4 kits (which equals the highest known litter size in the western US). Survival one year after reintroduction was high in the South Cascades (76%), but lower than expected in the North Cascades (42%). Juvenile females represented the highest survival of all ages and across all cohorts, at 83% in the South Cascades, and 55% in the North Cascades. At the end of 2021, fishers were well distributed across much of the Cascades Fisher Recovery Area. Some animals were located enough times to determine that a home range had likely been established; and based on the consistent distribution within the recovery area through time, we can assume that many other fishers have settled into a home range that includes the west slope of the Washington Cascades.

Cascades fisher reintroduction project: Final project report

Series

See also

Collections