Pacific fisher (Pekania pennanti)

Get the latest news here on the status of efforts to protect the rare Pacific fisher, now endangered and at risk of extinction within the Sierra Nevada. Sierra Forest Legacy has been involved in efforts to protect fishers from continuing threats to their survival since 1992. Scroll down the page to read about current efforts to protect the fisher from extinction, the translocation project in Butte County, biology of the fisher, and links to supporting scientific and policy literature.

October 19, 2021

Today the U.S. Fish and Wildlife service announced that it is seeking public comment on a proposed rule to designate critical habitat for the Pacific fisher, southern Sierra Nevada distinct population segment (DPS), as required by the Endangered Species Act. The Service is recommending designation of 554,454 acres across portions of Fresno, Kern, Madera, Mariposa, Tulare and Tuolumne counties in California. Most of the proposed critical habitat is located on federally owned U.S. Forest Service or National Park Service public lands. Comments regarding the proposal will be accepted by the agency until December 20, 2021. Read the proposed rule, the specifics of how to submit comments, and find links to background information.

May 15, 2020

The U.S. Fish and Wildlife Service formally announced today the listing of the Distinct Population Segment (DPS) of the Pacific Fisher in the Southern Sierra Nevada region of California as an endangered species. Read the press release here, and the listing notice in today's Federal Register.

The fisher population in the Southern Sierra Nevada is currently estimated to be anywhere between 100 and 500 individuals.

November 7, 2019

The U.S. Fish and Wildlife Service today issued a revised proposed rule, availability of proposed section 4(d) rule, and reopening of comment period for the October 7, 2014, proposed rule to list the West Coast Distinct Population Segment (DPS) of fisher (Pekania pennanti) as a threatened species under the Endangered Species Act (Act).

The agency has proposed a “4(d) rule” after section 4(d) of the Act. This section allows the Service to identify exceptions to the “take” provisions for actions that the Service judges in the long term would benefit Pacific fishers, even if there were some short term losses in species’ numbers or habitat quality. The proposed exceptions are not very specific and allow logging and other actions that are not well defined. Of particular concern is the failure for the exceptions to account for cumulative effects and the potential for the Forest Service to ramp up their tree removal and other activities in coming years. We are reviewing the exceptions with our partners and will be submitting comments on the rule at the beginning of December.

See our joint press release with the Center for Biological Diversity.

Link to the Federal Register with the proposed rule.

September 21, 2018

Fisher protection is back on track. Today a federal judge in the Northern District of California ruled that the U.S. Fish and Wildlife Service must reconsider their denial of Endangered Species Act protection for Pacific fishers. The Service proposed federal protection for the fisher in 2014, but then arbitrarily withdrew the proposal in 2016. Groups then filed suit (see below) alleging that the denial ignored the science in a politically motivated bow to the timber industry. As the result of today’s ruling, the agency must issue a new decision for the fisher by March 22, 2019.

Pacific fishers are threatened by the use of toxic rodenticides by marijuana growers, and increasing fire severity exacerbated by climate change, along with loss of habitat due to logging.

In today’s decision the judge emphasized that the Service downplayed the threat to fishers from rodent poisons in determining that federal protection was not warranted. But in a 2015 study, scientists conducting necropsies on fishers found that 85 percent had been exposed to rodent poison.

Efforts to gain federal protection for the fisher now span decades. The Center for Biological Diversity first petitioned to protect the fisher in 1994, and again in 2000, joined by the three other groups on the lawsuit, the Environmental Protection Information Center, Klamath-Siskiyou Wildlands Center and Sierra Forest Legacy. The groups were represented by Earthjustice.

Download the court order here.

October 19, 2016

Today, Sierra Forest Legacy and our coalition partners filed suit in U.S. District Court challenging the U.S. Fish and Wildlife Service's decision to deny Endangered Species Act protection for Pacific fishers (see below). Read the complaint here, and today's press release here.

Read the 60-day Notice of Intent here (filed June 13, 2016), and press release here.

April 20, 2016

The Pacific fisher, Southern Sierra Nevada population, has at long last obtained protection under the California Endangered Species Act. Today the California Fish and Game Commission issued a final conclusion to the 2008 petition to list the Pacific fisher as a threatened species. The Commission's determination in its notice of findings today states: "[T]here is sufficient scientific information to indicate that designating the Southern Sierra Nevada fisher evolutionarily significant unit as a threatened species under CESA is warranted at this time and that with adoption and publication of these findings the Southern Sierra Nevada fisher evolutionarily significant unit of fisher for purposes of its legal status under CESA and further proceedings under the California Administrative Procedure Act, shall be listed as threatened." Read the findings, and background documents associated with the listing process here.

April 18, 2016

Today the U.S. Fish and Wildlife Service issued its conclusion that the Pacific fisher will not be listed as a threatened or endangered species under the Endangered Species Act. Citing "the best scientific and commercial information available," the FWS found that the stressors impacting the fisher and its habitat are "not of sufficient magnitude, scope, or imminence" to indicate that the species is in danger of extinction, either now or in the forseeable future.

This is an untenable conclusion, given the large volume of scientific studies documenting the decline and growing threats to the fisher. This is clearly a politically motivated decision. Over the last 16 years, the last two federal administrations have been characterized by an ideological opposition to species' listings, demonstrating an unscientific bias favoring the demands of industry special interests.

The federal register notice can be downloaded here, and supporting literature and public comments can be viewed at this FWS website.

April 2, 2016

Recently the US Fish and Wildlife Service requested comments on a "Candidate Conservation Agreement with Assurances," or CCAA, proposed by Sierra Pacific Industries (SPI). The agreement would cover all of the company's lands outside the coastal region (1.57 million acres). At the same time comments were solicited for the accompanying Environmental Assessment also submitted by SPI. Download the March 2, 2016 Notice of Availability published in the Federal Register. Read our comments on the proposal here.

The proposal comes within days of the anticipated formal listing of the Pacific fisher as a species threatened with extinction. The agreement, if accepted by FWS, would grant timber company Sierra Pacific Industry exemption from the anticipated conservation requirements of the Endangered Species Act after the species is formally isted, for a period of ten years.

The CCAA provides participating property owners with a permit containing assurances that if they engage in certain conservation actions for species that are currently not listed, "they will not be required to implement additional conservation measures beyond those in the CCAA" and "additional land, water, or resource use limitations will not be imposed on them" after the species is listed.  

The type of logging primarily practiced by Sierra Pacific Industries, "even-aged management," is known to reduce or degrade suitable forest habitat for Pacific fisher, since it involves clearcutting and replacing native forest with uniform tree plantations of ponderosa pine, along with regular applications of herbicides to kill forest vegetation. SPI management has consistently failed to preserve the types of trees that provide good denning and resting sites for the imperiled fisher.

Download the CCAA and EA here.

February 15, 2016

The Fisher Technical Team has completed Version 1.0 of the Fisher Conservation Strategy. The 15.0 MB document can be downloaded here. Learn more about the interagency Southern Sierra Nevada Fisher Conservation Assessment and Strategy here.

June 10, 2015

After the 2008 listing petition before the California Department of Fish and Wildlife, and the subsequent lawsuit we brought with the Center for Biological Diversity in 2010, the agency completed the required status review for the Pacific fisher and concluded that listing the Southern Sierra ESU (Evolutionary Significant Unit) as a threatened species is warranted.

January 21, 2015

The Southern Sierra Fisher Conservation Assessment, which summarizes the current state of knowledge about fishers and fisher habitat in the southern Sierra Nevada, has been released. Download and read the document here.

October 6, 2014

It's official: after many years of cautious study and analysis harkening all the way back to 1994, the U.S. Fish and Wildlife Service announced today plans to list the West Coast distinct population segment of the fisher as a species threatened with extinction under the Endangered Species Act. Here is the offiical notice in the Federal Register, published October 7, 2014. The FWS a lot of information on their website, with videos and FAQs about the fisher. Please scroll through the posts on this page for additional information about the history of the petition to seek protection for this beautiful and rare mammal. The Fisher Technical Team is led by Wayne Spencer of Conservation Biology Institute.

June 2013

The Southern Sierra Fisher Conservation Strategy Project has been convened as an inter-agency and multi-disciplinary effort to assess current information and develop a conservation strategy for the isolated population of Pacific fisher (Martes pennanti) in the Southern Sierra Nevada, California.  The group consists of a Fisher Inter-Agency Leadership Team (FIALT), a Fisher Technical Team (FTT) led by Wayne Spencer of the Conservation Biology Institute, and a Core Support Team (CST).  Susan Britting, SFL's executive director, is also a member of the Fisher Technical Team. Read the charter here.

March 21, 2013

In ruling on a lawsuit filed by Earthjustice on behalf of the Center for Biological Diversity in 2010, a California Superior Court today declared Pacific fishers to be indeed eligible candidate species requiring protection under the California Endangered Species Act (CESA). The California Fish and Game Commission must now determine whether to protect fishers permanently as threatened or endangered. The ruling is the result of lawsuit filed by Earthjustice on behalf of the Center for Biological Diversity.

January 2012

West Coast Fisher Symposium January 31 - February 1, 2012

Download the presentations at this website.

Also read the latest state of the science literature for conservation of fisher now available in three volumes from U.S. Fish and Wildlife Service. Click on the titles below to download. Volume I is 27.8 MB so it may take some time to download depending upon your connection speed.

Lofroth, E. C., C. M. Raley, J. M. Higley, R. L. Truex, J. S. Yaeger, J. C. Lewis, P. J. Happe, L. L. Finley, R. H. Naney, L. J. Hale, A. L. Krause, S. A. Livingston, A. M. Myers, and R. N. Brown. 2010. Conservation of Fishers (Martes pennanti) in South-Central British Columbia, Western Washington, Western Oregon, and California–Volume I: Conservation Assessment. USDI Bureau of Land Management, Denver, Colorado, USA.

Lofroth, E. C., J. M. Higley, R. H. Naney, C. M. Raley, J. S. Yaeger, S. A. Livingston, and R. L. Truex. 2011. Conservation of Fishers (Martes pennanti) in South-Central British Columbia, Western Washington, Western Oregon, and California–Volume II: Key Findings From Fisher Habitat Studies in British Columbia, Montana, Idaho, Oregon, and California. USDI Bureau of Land Management, Denver, Colorado, USA.

Naney, R. H., L. L Finley, E. C. Lofroth, P. J. Happe, A. L. Krause, C. M. Raley, R. L. Truex, L. J. Hale, J. M. Higley, A. D. Kosic, J. C. Lewis, S. A. Livingston, D. C. Macfarlane, A. M. Myers, and J. S. Yaeger. 2012. Conservation of Fishers (Martes pennanti) in South-Central British Columbia, Western Washington, Western Oregon, and California–Volume III: Threat Assessment. USDI Bureau of Land Management, Denver, Colorado, USA.

May 25, 2011

Kings River Fisher Project -- Progress Report

Researchers Craig Thompson, Kathryn Purcell, James Garner and Rebecca Green from the Sierra Nevada Research Center of the U.S. Forest Service have just released a progess report on 72 radio-collared fisher which they have been studying since 2007. The project area is located in the Kings River area, west of Shaver Lake in the High Sierra Ranger District of the Sierra National Forest.

The purpose of this study is to learn more about fisher ecology including their habitat requirements, and to increase understanding about the effects of timber harvest and fuels treatments on select response variables of interest, including fishers and their habitat.

The report is too large to post here (30 MB) but it can be downloaded from this website until June 22. Here's an excerpt from the summary:

"Using a combination of telemetry and scat dog data, we generated a preliminary density estimate of 13.4 fishers per 100 km². We observed reproductive activity for 79% of the adult females monitored during two breeding seasons, with 45 kits observed at 31 natal dens. We located an additional 64 maternal dens in a variety of structures. Survival rates ranged from 0.61 for subadult males to 1.0 for juvenile females, and predation accounted for 81% of all mortality. Genetically confirmed predators include mountain lion (40%), bobcat (40%), and coyote (20%).

We generated 95% kernel home range estimates of 1,113 ha for females and 4,522 ha for males. In agreement with most published literature, fishers were found in areas of higher canopy cover. However they were also found more often in areas with higher number of small (<20” dbh) trees, indicating that these trees may provide requisite structure and canopy. Fishers avoided edges, particularly with respect to resting sites, and were found on the lower portions of north facing slopes more often than any other topographic position. Fishers used a variety of tree species and structures for resting, with the most common choices being cavities in black oak and white fir. Diet was dominated by mammalian remains, though we documented a large diversity in food consumed including plants, birds, reptiles, and insects."

June 23, 2010

The California Fish and Game Commission voted 3-1 in favor of California DFG's decision not to list the fisher.

April 8, 2010 -- Lawsuit Filed to Expedite Protection of Pacific Fisher

For Immediate Release

Noah Greenwald, Center for Biological Diversity, (503) 484-7495
Craig Thomas, Sierra Forest Legacy, (530) 622-8718
Scott Greacen, EPIC, (707) 822-7711
George Torgun, Earthjustice, (510) 550-6700

SAN FRANCISCO, California -- A coalition of conservation groups filed a lawsuit today asserting that the U.S. Fish and Wildlife Service is illegally delaying Endangered Species Act protection for the Pacific fisher, a relative of the mink and otter that has been decimated by historic fur trapping and logging of old-growth forests. The groups filing the lawsuit are the Center for Biological Diversity, Sierra Forest Legacy, Environmental Protection Information Center, and Klamath-Siskiyou Wildlands Center, represented in court by the law firm Earthjustice.

In response to a 2000 petition from the groups, the U.S. Fish and Wildlife Service acknowledged in 2004 that the fisher warranted protection under the Endangered Species Act but claimed such protection was precluded by listing of other species considered a higher priority. Hundreds of species have been caught in the purgatory of this “warranted but precluded” designation.

“The fisher and hundreds of other species have been waiting too long for protection,” said Noah Greenwald, endangered species program director at the Center for Biological Diversity. “Continued delay of protection for the fisher puts the survival of this unique animal in jeopardy.”

Species designated as warranted but precluded are placed on a list of species considered candidates for listing, which currently includes 252 species. On average, these species have been waiting 20 years for protection. Candidate designation does not provide any protection. Both the Bush and Obama administration cited lack of resources as the basis for continuing to delay protection for these species. But the facts are contrary to this claim, since the budget for listing species has gone up by nearly 200 percent since 2002 and far more species used to be listed. To date, only two species have been protected under the Endangered Species Act under the Obama administration. By comparison, the Clinton administration protected an average of 65 species per year and a total of 522 species.

“Secretary Salazar is not prioritizing protection of endangered species,” said Greenwald. “With threats from habitat loss, pollution, invasive species, and climate change all on the rise, we can’t afford to neglect the nation’s wildlife.”

The fisher once roamed from British Columbia to the southern Sierra. Today, it has been reduced to three native populations found in the southern Sierra Nevada, northern California and southwestern Oregon, and thanks to a reintroduction effort, Washington’s Olympic National Park. These populations continue to be threatened by logging.

“The Pacific fisher has been devastated by a combination of historic fur trapping and logging of its old-growth forest habitats,” said Craig Thomas, executive director of Sierra Forest Legacy. “Without protection from continued logging on private and federal lands, the fisher will go extinct.”

“Two things are quite clear at this point for the fisher,” said Scott Greacen, executive director of EPIC. “One, science has shown that current protections for fisher habitat on both industrial timberlands and national forests in California are clearly inadequate. Two, the timber industry, especially Sierra Pacific Industries, is doing everything in its power to prevent or delay any further protections for the species.”

“This marvelous, rare, and shy predator is a treasure of  our western wildlands,” said George Torgun of Earthjustice. “Depriving our grandchildren of the opportunity to glimpse this reclusive animal would be shameful. The Pacific fisher deserves protection now.”

A close relative of the mink and otter, the fisher (Martes pennanti) is a shy predator with a diverse diet that includes porcupines and other small forest animals, carrion, vegetation, fungi, and fruit. The Pacific fisher’s historic distribution on the West Coast included all of western Washington and Oregon, northwestern California, and the Sierra Nevada, but is now much reduced.

The fisher has a long, slender body with short legs. Its head is triangular, with a sharp, pronounced muzzle and large, rounded ears. Fishers are mostly brown, with a long, bushy tail. Males range up to 47 inches in length, while females typically only reach 37 inches. Fishers run in a bounding gait, with their front feet leaping forward together, followed by the back feet.

Because fishers are the only animal that regularly prey on porcupines, which often kill or damage small trees, the timber industry reintroduced the fisher to many parts of the United States, including the southern Cascades of Oregon. The fisher kills porcupines with repeated bites to the face, devouring the porcupine via the quill-less underbelly. Where fisher reintroductions have been successful, porcupines have indeed declined in number.

Read the legal complaint here.

Feb 4, 2010-- Read the Notice of Intent to file here.

March 31, 2010 -- Wildlife experts say the DFG status report was altered by state officials to favor the logging industry.

Read the report from the Sacramento Bee.

March 2, 2010 -- California Denies Protection to the Fisher under California's Endangered Species Act

California's Department of Fish and Game has completed its review of the status of the Pacific fisher, concluding "The Department recommends to the Fish and Game Commission that designation of the fisher in California as threatened/endangered is not warranted."

The Department had determined last March (2009), that the fisher qualified as a candidate species under the California Endangered Species Act, in response to a petition filed by the Center for Biological Diversity in 2008. You can read the final decision/status review here.

Watch this video presentation by wildlife researcher Katie Moriarty at Sagehen Creek Research Station. As Moriarty warns, the research is clear that the Pacific fisher (Sierra Nevada population) is deserving of listing protection under the state and federal endangered species acts. This excellent presentation discusses American marten, Pacific fisher, wolverine, and Sierra Nevada red fox.

American Marten research in Sagehen Basin. from F. Felix on Vimeo.

January 7, 2010 - Conservationists Defeat Attack on Pacific Fisher

Rare relative of the mink and otter still waiting for protection

San Francisco, CA -- The Ninth Circuit Court of Appeals turned down an effort by a timber mill and an anti-wildlife group to preclude the Pacific fisher, a rare relative of the otter and mink, from ever being protected under the Endangered Species Act. In 2004, the U.S. Fish and Wildlife Service determined that the fisher warrants protection as a threatened or endangered species under the Endangered Species Act (ESA) but refused to finalize such protection. The defeated lawsuit had hoped to ensure that protection for the fisher would never be finalized. 

"The fisher is in need of immediate protection under the Endangered Species Act to survive," said Greg Loarie, attorney with Earthjustice. "We're glad that this effort to stop protection for the fisher was stopped in its tracks."

The Center for Biological Diversity, Sierra Forest Legacy and other groups first petitioned to have the fisher protected in 2001. Litigation later brought by Earthjustice eventually resulted in the "warranted but precluded" finding from the U.S. Fish and Wildlife Service. Sierra Forest Products challenged the finding, saying the U.S. Fish and Wildlife Service didn't have the  authority to consider the Pacific fisher a "distinct population segment" eligible for listing under the ESA. In June 2007, Earthjustice intervened in this lawsuit to defend the fisher. A year later the district court rejected Sierra Forest Products' challenge to the listing. Sierra Forest Products subsequently appealed to the Ninth Circuit Court of Appeals and today was tossed out of court.

With the warranted but precluded finding, the fisher is now one of 249 species for which protection has been delayed by the U.S. Fish and Wildlife Service. During its eight year tenure, the Bush administration protected a mere 62 species, for a rate of less than eight species per year. This compares to 522 protected under the Clinton administration at a rate of 65 species per year; and 231 species protected under the George H.W. Bush administration at a rate of 58 species per year. 

The fisher formerly ranged throughout old-growth forests of Washington, Oregon, northwestern California and the Sierra Nevada. Because of a combination of logging and historic fur-trapping, the fisher is now gone from all of Washington, most of Oregon and half its range in California. It is now found in two disconnected populations -- one in northwestern California and extreme southwestern Oregon, and another in the southern Sierra Nevada.

Earthjustice represented the Center for Biological Diversity, Sierra Forest Legacy, NRDC, and the Sierra Club.

Greg Loarie, Earthjustice, (510) 550-6790
Noah Greenwald, Center for Biological Diversity, (503) 484-7495

Status Update on the fisher re-location in Butte County

May 2013 -- The latest status report for the period October 2009 - January 2013 reports out of a total of 40 fisher captured and released in the Stirling tract area of Butte County, the population is now estimated to be 37, which includes 7 of the original adults and 13 juveniles that have been born since the introduction, and that were successfully recaptured and recollared or implanted with transmitters. Through year 3, the research team located the carcasses of 11 dead fisher, and analyses were conducted to determine the cause of death. One fisher died of an unknown systemic disease, another was predated upon by a bobcat; however 3 of 4 fisher tested positive for the presence of anticoagulant rodenticides. These rodent poisons are used to control mice and rats around cannibis plantations, but are also widely used in homes, resort and vacation buildings, businesses, etc. Learn more about this significant threat to fisher and other wildlife here.

Other highlights of the report document an overwhelming preference for black oak for both maternal and natal denning sites.

January 2012 -- Keep track of the fisher relocation project at Aaron Facka's blog, here.

May 2011 -- Out of a total of 28 fisher that were released since 2010, it appears that only 18 can be documented as having survived to date, according to a status report just released. Thus far 6 documented kits have been observed and 5 females and 3 males have survived the 2010 releases. All 7 females survive from this year's release, one male has died, and 3 males cannot be confirmed because their radio transmitters have malfunctioned as of April 2011. The website now contains field notes from researcher Aaron Facka and many pictures and video of the release effort. It is not presently known where the northernmost male fisher is located. Ironically, this fisher moved to the site of two contested timber harvest plans, the Lookout and Long Ridge THPs, in Tehama County north of the release site. The region contains large stands of high quality fisher habitat that will be completely removed during clearcutting operations planned by the land owner, Sierra Pacific Industries.

January, 2011 -- Another 13 fisher, 7 females and 6 males, were captured from the Coast Ranges and released in the same location in Butte County.

September, 2010 -- CDFG now has a website with information on the Butte County fisher translocation. Three females have been found dead, ten animals have disappeared, and one juvenile appeared to survive, although 4 females had thought to be denning during the summer.

June 29, 2010 -- One female, without kits, was found dead today.

June 10, 2010 -- To date, 4 females have been observed with newborn kits in the region where they were released in Butte County. All four utilized large old trees with cavities for natal denning sites. Here you can download a poster that fisher researchers, Aaron Facka and Roger Powell, put together. You can also read more about the reintroduction in the July 2010 Sierra Voice, and we will post more information about the fishers here as soon as it is available.

March 2010 -- Between November 23, 2009 and January 20, 2010, sixteen Pacific fisher were captured in Siskiyou and Trinity Counties by personnel from the Calif. Department of Fish and Game and U.S. Fish and Wildlife Service. To date, fifteen fisher have been released in Butte County. One female has died in captivity. The females were surgically implanted with radio transmitters in their abdomens. Males have radio transmitter collars. These emit GPS signals that enable the researchers to track them.

Four females and one male were trapped from a region south of Hwy 96 and Klamath, in Siskiyou County. Eleven more fishers were trapped northwest of Buckhorn Summit, and in two areas north and south of Hwy 3 between Hayfork and Weaverville in Trinity County, netting six females and five males.

Fifteen of the captured Pacific fishers have now been released onto Sierra Pacific Industries forest lands located between Hwy 32 and The Skyway Road, and Hwy 70.

The released fisher have begun to move onto publicly owned, protected forests in the Plumas National Forest.

The U.S. F&WS and CDF&G are currently working on development of a website that will allow the public access to real time information about the status of the fisher translocations. Read more about the project in the document files listed at the end of this page.

July 21, 2009 - California Department of Fish and Game issued a Notice of Determination to go forward with the plan to capture 40 fishers over a three year period, place radio transmitter collars in them, and release them on SPI forest lands in the Stirling Tract region of Butte County.

January 9, 2009 - The California Department of Fish and Game has released a Notice of Intent (Jan. 9) to approve a controversial plan to permit the capture and release of 40 Pacific fisher on lands owned by Sierra Pacific Industries (SPI) in the Northern Sierra Nevada. The plan provides the company with assurances of no new restrictions on logging activities within the 250 square mile region where the release will occur (the "Stirling Tract") -- even if the Pacific fisher is listed under the Endangered Species Act in the future. Conservationists and scientists agree that the plan makes no sense. Why not simply introduce the fisher on national forest lands?

Read SFL's comments here.

Visit the Action Alert page for more information and additional reading materials.

Life History

Pacific fisher The rarely encountered Pacific fisher is in the family Mustelidae, the largest member of the genus Martes. The only other North American member of the genus Martes is the American marten (M. americana). The fisher is light brown to dark blackish brown with the face, neck, and shoulders sometimes being slightly gray. The chest and underside often has irregular white patches. The fisher has a long body with short legs and a long bushy tail. At 6.6 to 13.2 pounds, male fishers weigh about twice as much as females (3.3 to 5.5 lbs). Males range in length from 35 to 47 inches while females range from 29 to 37 in long. Fishers are estimated to live up to 10 years.

The diet of the fisher includes birds, snowshoe hares, squirrels, mice, shrews, voles, porcupines, reptiles, insects, carrion, vegetation, and fruit. Fishers hunt exclusively in forested habitats and generally avoid openings. Being dietary generalists, fishers tend to forage in areas where prey is both abundant and vulnerable to capture. Selection of foraging habitat may be driven by habitat relationships of primary prey species.

Except during the breeding season, fishers are solitary animals. The breeding season for the fisher is generally from late February to the end of April. Raised entirely by the female, kits are completely dependent at birth and weaned by 10 weeks. The mother becomes increasingly active as kits grow in order to provide enough food, and females may move their kits periodically to new dens. At 1 year, kits will have developed their own home ranges. Fishers have a low annual reproductive capacity, and reproductive rates may fluctuate widely from year to year.


The fisher, a relative of the mink, otter, and marten, is a predator dependent upon mature and old growth forests for habitat. Fishers use large areas of primarily coniferous forests with fairly dense canopies and large trees, snags, and down logs. The fisher prefers mature and old-growth forests with high canopy cover, and requires large trees for denning. The fisher dens in rotting logs, hollow trees, and rocky crevices of old growth forests. They are specialized animals that frequently travel along waterways and rest in or on live trees, snags, or logs with cavities. These characteristics are usually only found in large, undisturbed tracts of old forest. Douglas fir is the most common species used for resting in northern California, whereas oak, white fir, and red fir are commonly used in the southern Sierra. The diameter of trees used by fisher for resting and denning is consistently large. Rest sites are widely distributed throughout fisher habitat.

Each individual travels over a home range of 50-150 square miles, even more in winter when food is scarce. A home range is an area repeatedly traveled by an individual in its normal activities (i.e. feeding, drinking, and resting). Fishers have large home ranges and male home ranges are considerably larger than those of females. Fisher home range sizes across North America vary from 3,954 to 30,147 acres (16 to 122 square kilometers for males and from 988 to 13,096 ac (4 to 53 square km for females).

Rest sites are natural structures that provide protection from unfavorable weather and predators. Re-use of rest sites are relatively low (14 percent: Zielinski et al. 2004), indicating that habitats providing suitable resting structures need to be widely distributed throughout home ranges of fishers and spatially interconnected with foraging habitats.

Rest site structures used by fishers include: cavities in live trees, snags, hollow logs, fallen trees, canopies of live trees, platforms formed by mistletoe (‘‘witches brooms’’) or large or deformed branches, and to a lesser extent stick nests, rocks, ground cavities, and slash and brush piles. Tree size, age, and structural features are important characteristics of a rest structure. Zielinski et al. (2004) stated that rest structures in their study areas in the North Coast and the southern Sierra Nevada were among the largest diameter trees available. Trees must be large and old enough to bear the type of stresses that initiate cavities, and the type of ecological processes (e.g., decay, woodpecker activity) that form cavities of sufficient size to be useful to fishers; tree species that typically decay to form cavities in the bole are more important than those that do not.

The most influential variables affecting rest site selection in California fisher populations include maximum tree sizes and dense canopy closure, but other features are important to rest site choice as well, such as large diameter hardwoods, large conifer snags, and steep slopes near water. Fishers select areas as rest sites where structural features are most variable but where canopy cover is least variable, suggesting that resting fishers place a premium on continuous overhead cover but prefer resting locations that also have a diversity of sizes and types of structural elements (Zielinski et al. 2004).


The west coast population of the Pacific fisher is endangered due to habitat loss and fragmentation, small population sizes and isolation, and human-caused mortality from incidental trapping and vehicle collisions. Timber harvest can fragment fisher habitat, reduce it in size, or change the forest structure to be unsuitable for fishers. Fisher are also reluctant to cross open areas to recolonize historical habitat. Logging and development have caused severe loss and fragmentation of old-growth forests--as little as 5 percent of this forest type remains in the Sierra Nevada. Stand replacing wildfires, as well as management activities designed to prevent such fires by reducing the amount and continuity of forest fuels, all can result in significant reduction in suitable habitat needed to provide for fisher viability. The complex and probabilistic interplay between such habitat threats, as well as incomplete information on fisher biology, creates great uncertainty about the current health of the southern Sierra fisher population and how it is likely to change in the future. Global climate change is also predicted to have severe impacts in the Sierra Nevada, with greatly reduced snow pack in the winter and increased drought and wildfires in the region, thereby underscoring the need to protect the remaining habitat for this species and others that also require old forest attributes.


The Bush Administration’s 2004 Sierra Nevada Framework revisions have increased logging in old growth forests throughout the Sierra Nevada and particularly in key fisher habitat. The revisions to the 2001 Framework plan dismantle the Southern Fisher Conservation Area, which until the revisions were adopted, helped protect forests throughout existing fisher habitat. The revisions also increased off-highway vehicle use and road construction within the fisher’s home ranges. Severe loss and fragmentation of habitat caused by logging has lead to the near extinction of the fisher from its west coast range.  The species has less dispersal power compared to another imperiled species, the California spotted owl, and they are comparatively slow to recolonize their historic range. Because the fisher cannot fly over logged areas, it is considerably more sensitive to fragmentation of old forests than the owl. In the Sierra Nevada, fishers currently occupy less than half their historic range, with a gap of 350 miles separating the northern and southern California populations (Zielinski et al. 2005).  Having apparently been extirpated from the central and northern Sierra, a small population does persist in the southern Sierras, south from Yosemite National Park to the vicinity of the Greenhorn Mountains in southern Tulare County. The initial Giant Sequoia National Monument plan advanced by the Bush Administration sought to dramatically increase logging within the core habitat of remaining fisher populations in the southern Sierra Nevada. The Pacific fisher depends upon forest management decisions which ensure the protection of large, continuous blocks of mature and old growth forests.

Restoring and managing preferred forest habitats throughout the Sierra is essential to conserve the fisher. Maintaining connectivity of habitats is important to enable the fisher to recolonize the central and northern Sierra from the fisher populations in the south. Conservation of the fisher also necessitates protecting and restoring the black oak woodlands component of mixed-conifer forest ecosystems, conserving large deformed trees, and reestablishing patches of lush layered ground vegetation, snags, and fallen logs to provide conditions for abundant prey.


Currently, only three small, isolated populations of the Pacific fisher remain, including native populations in northwestern California and the southern Sierra Nevada and a reintroduced population in the southern Oregon Cascades. An analysis by Forest Service researchers indicates that, in the absence of stronger protection measures, the fisher is likely to become extinct in the southern Sierra within 50 years.

In 2004, the U.S. Fish and Wildlife Service found that the west coast distinct population segment of the fisher "may be at significant risk of extinction" and that protection under the Endangered Species Act is "warranted,” but that listing the species was precluded by higher priorities. For the first time in the history of the Endangered Species Act, a presidential administration, the Bush Administration, has not listed a single species as threatened or endangered without being forced to do so through petitions and/or litigation. And without a doubt, this administration also holds the worst record for the number of imperiled species it has listed while in office. A "warranted but precluded" determination (like the one the FWS made for the fisher) is only allowed if the FWS is making "expeditious progress" towards listing other species. Clearly that requirement for the warranted but precluded status is not remotely close to being fulfilled. Read SFL's and our conservation partners' response here.

Iin March 2013, a California court agreed with scientists and conservationists, ruling that the fisher is a candidate for listing under the state Endangered Species Act, CESA. In 2008, the Center for Biological Diversity (CBD) petitioned to have the Pacific fisher listed as endangered under the California's Endangered Species Act. Although state biologists determined that listing the rare fisher was necessary for its survival, officials in the agency overruled their findings and decided not to give the fisher protection in 2010. Earthjustice filed suit, and in March 2013, the Superior Court ruled that the fisher is indeed a candidate for listing under CESA. It remains to be seen how the state agency charged with overseeing timber harvests on private timber lands will respond to this finding.

Scientific Research

Aubry, K.B. 2005. Fisher Conservation Populations in the Pacific States: Field Data Meet Genetics. U.S. Forest Service, Pacific Northwest Research Station. Science Findings, Issue 70. (KB PDF)

Boroski, B.B., 2002.  Fisher Research and the Kings River Sustainable Forest Ecosystems Project: Current Results and Future Efforts. U.S. Forest Service Gen. Tech. Rep. PSW-GTR-183. (3.1MB PDF)

Carroll, C. 2005. A Reanalysis of Regional Fisher Suitability Including Survey Data From Commercial Forests in the Redwood Region. U.S. Forest Service, Pacific Southwest Research Station, Redwood Sciences Laboratory, Arcata, California. 18pp. (50KB PDF)

Conservation Biology Institute. 2007. Southern Sierra Nevada Fisher Baseline Assessment: Final Report. Baseline Evaluation of Fisher Habitat and Population Status in the Southern Sierra Nevada Fisher Assessment. Conservation Biology Institute, Corvalis, Oregon. 62 pp. (3.64MB PDF)

Conservation Biology Institute. 2007. Appendices to the Southern Sierra Nevada Fisher Baseline Assessment: Final Report. Baseline Evaluation of Fisher Habitat and Population Status in the Southern Sierra Nevada Fisher Assessment. Conservation Biology Institute, Corvalis, Oregon. 78 pp. (1.91MB PDF).

Gabriel, M.W., L. W. Woods, R. Poppenga, R. A. Sweitzer, C. Thompson, S. M. Matthews, J. M. Higley, S. M. Keller, K. Purcell, R. H. Barrett, G. M. Wengert, B. N. Sacks, and D. L. Clifford. 2012. Anticoagulant Rodenticides on our Public and Community Lands: Spatial Distribution of Exposure and Poisoning of a Rare Forest Carnivore. PLoS One 7:7. Article Number: e40163. ( (17.5 MB PDF)

Green, D.S., Martin, M.E., Powell, R.A., McGregor, E.L., Gabriel, M.W., Pilgrim, K.L., Schwartz, M.K. and Matthews, S.M., 2022. Mixed‐severity wildfire and salvage logging affect the populations of a forest‐dependent carnivoran and a competitor. Ecosphere13(1), p.e03877.

Keller, S. M., M. Gabriel, K. A. Kerio, E. J. Dubovi, E. Van Wormer, R. A. Sweitzer, R. H. Barret, C. Thompson, K. Purcell, and L. Munson. 2012. Canine distemper in an isolated population of fishers (Martes pennanti) from California. Journal of Wildlife Diseases 48(4): 1035–1041 (1.09 MB PDF).

Koepfli, K-P., et al. 2008. Multigene phylogeny of the Mustelidae: Resolving relationships, tempo and biogeographic history of a mammalian adaptive radiation. BMC Biology 2008, 6:10. (567 KB PDF)

Lofroth, E. C., C. M. Raley, J. M. Higley, R. L. Truex, J. S. Yaeger, J. C. Lewis, P. J. Happe, L. L. Finley, R. H. Naney, L. J. Hale, A. L. Krause, S. A. Livingston, A. M. Myers, and R. N. Brown. 2010. Conservation of Fishers (Martes pennanti) in South-Central British Columbia, Western Washington, Western Oregon, and California–Volume I: Conservation Assessment. USDI Bureau of Land Management, Denver, Colorado, USA.

Lofroth, E. C., J. M. Higley, R. H. Naney, C. M. Raley, J. S. Yaeger, S. A. Livingston, and R. L. Truex. 2011. Conservation of Fishers (Martes pennanti) in South-Central British Columbia, Western Washington, Western Oregon, and California–Volume II: Key Findings From Fisher Habitat Studies in British Columbia, Montana, Idaho, Oregon, and California. USDI Bureau of Land Management, Denver, Colorado, USA.

Naney, R. H., L. L Finley, E. C. Lofroth, P. J. Happe, A. L. Krause, C. M. Raley, R. L. Truex, L. J. Hale, J. M. Higley, A. D. Kosic, J. C. Lewis, S. A. Livingston, D. C. Macfarlane, A. M. Myers, and J. S. Yaeger. 2012. Conservation of Fishers (Martes pennanti) in South-Central British Columbia, Western Washington, Western Oregon, and California–Volume III: Threat Assessment. USDI Bureau of Land Management, Denver, Colorado, USA.

Powell, R.A., and W.J. Zielinski. 1994. The Scientific Basis for Conserving Forest Carnivores: American Marten, Fisher, Lynx, and Wolverine in the Western United States. Gen. Tech. Rep. RM-254. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. pp. 38-73. (838KB PDF)

Powell, R.A., S.W. Buskirk, and W.J. Zielinski. 2003. Fisher and Marten. In: Wild Mammals of North America: Biology, Management, and Conservation. The Johns Hopkins University Press. Pp. 635-649. (3MB PDF)

Purcell, K.L., Mazzoni, A.K., Mori, S.R., and B.B. Boroski. 2009. Resting structures and resting habitat of fishers in the southern Sierra Nevada, California. Forest Ecology and Mgmt. 258(12):2696-2706. (550 KB PDF)

Safford, H.D. 2006. Potential Impacts of Climate Change to Fisher Habitat in California: A Preliminary Assessment. U.S. Forest Service Pacific Southwest Region. 29pp. (657KB PDF)

Spencer, W.D. et al.2008. ("CBI Fisher Report") Baseline evaluation of fisher habitat and population status, and effects of fires and fuels management on fishers in the southern Sierra Nevada. Conservation Biology Institute. Unpublished report prepared for USDA Forest Service, Pacific Southwest Region. 133 pp + appendices. (5MB PDF)

Appendices for Spencer et al. "CBI Fisher Report" (above) (3.42MB PDF).

Sweitzer, R.A., C. Thompson, K. Purcell, M. Gabriel, G. Wengert, and R. Barrett. 2011. Survival & causes of mortality for “Pacific” fishers in the southern Sierra Nevada, California. Presentation given at The Western Section Wildlife Society Riverside, CA. February 2011.

Thompson, C.M. 2013. Sierra Nevada Adaptive Management Project Fisher Team Webinar Update.

Thompson, C., Smith, H., Green, R., Wasser, S. and Purcell, K., 2021. Fisher use of postfire landscapes: implications for habitat connectivity and restoration. Western North American Naturalist81(2), pp. 225-242.

Truex, R.L., and W.J. Zielinski. 2005. Short-term Effects of Fire and Fire Surrogate Treatments on Fisher Habitat in the Sierra Nevada. U.S. Forest Service, Joint Fire Science Program. 26pp. (405KB PDF)

Wengert, G.M., et al. 2014. Using DNA to Describe and Quantify Interspecific Killing of Fishers in California. Journal of Wildlife Management 78(4):603–611. (282 KB PDF)

Wisely, S.M. 2004. Genetic Diversity and Structure of the Fisher (Martes Pennanti) in a Peninsular and Peripheral Metapopulation. Journal of Mammology, 85(4): 640-648. (550KB PDF)

Zielinski, W.J., T.E. Kucera, and R.H. Barrett. 1995. Current Distribution of the Fisher, Martes Pennanti, in California. California Fish and Game 81(3) 104-112. (815KB PDF)

Zielinski, W.J. 2004. Home Range Characteristics of Fishers in California. Journal Of Mammalogy, 85(4), 649-65. (489KB PDF)

Zielinski, W.J., and N.P. Duncan. 2004. Diets of Sympatric Populations of American Martens (Martes Americana) and Fishers (Martes Pennanti) in California. Journal of Mammalogy 85(3) 470–477. (105KB PDF)

Zielinski, W.J. 2004.  Resting Habitat Selection by Fishers in California.  Journal of Wildlife Management 68(3):475-492. (3.38MB PDF)

Zielinski, W.J., J. Werren, and T. Kirk. 2005. Selecting Candidate Areas for Fisher (Martes pennanti) Conservation that Minimize Potential Effects on Martens (M. americana). U.S. Forest Service, Pacific Southwest Research Station, Redwood Sciences Laboratory, Arcata, CA (732KB PDF)

Zielinski, W.J., 2005. Historical and Contemporary Distributions of Carnivores in Forests of the Sierra Nevada, California, USA. Journal of Biogeography 32, 1385–1407. (8MB PDF)

Zielinski W.J., C. Carroll, and J.R. Dunk. 2006. Using landscape suitability models to reconcile conservation planning for two key forest predators. Biological Conservation. 22pp. (2.35KB PDF)

Zielinski, W.J., R.L. Truex, J.R. Dunk, and T. Gaman. 2006. Using Forest Inventory Data to Assess Fisher Resting Habitat Suitability in California. Ecological Applications. 16pp. (391KB PDF)

Zielinski, W.J., et al. 2010. Using forest inventory and analysis data and the forest vegetation simulator to predict and monitor fisher (Martes pennanti) resting habitat suitability. Gen. Tech. Rep. PSW-GTR-232. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 31 p. (1.21 MB PDF)

Zielinski, W.J., Baldwin, J.A., Truex, R.L., Tucker, J.M., and P.A. Flebbe. 2013. Estimating Trend in Occupancy for the Southern Sierra Fisher Martes pennanti Population. Journal of Fish and Wildlife Management 4(1):xx–xx; e1944-687X. doi: 10.3996/ 012012-JFWM-002 (9.5 MB PDF).

Supporting Resources

Fisher Reintroduction -- Candidate Conservation Agreement with Assurances

2010 Poster Presentation "Fishers Translocated to the Northern Sierra Nevada" by Aaron Facka and Roger Powell. Department of Biology, North Carolina University. (508 KB JPEG).

2010 Presentation "Translocation of Fishers into the Northern Sierra Nevada" for The Wildlife Society by DFG, FWS, and Univ. of North Carolina researchers Aaron Facka and Roger Powell (3.24 MB)

2009 Sierra Forest Legacy Comments on the Negative Declaration and Translocation Plan for the Reintroduction of Fishers to Sierra Pacific Industries Stirling Management Area (85 KB)

2009 CDFG Notice of Intent to Approve Negative Declaration for Reintroduction of Fishers (261 KB)

2008 CDFG Initial Study Negative Declaration (843 KB)

2008 FWS Candidate Conservation Agreement with Assurances for Fisher for the Sterling Management Area (1.08 MB)

2008 Center for Biological Diversity and Sierra Forest Legacy Comments on CCAA (123 KB)

2008 Defenders of Wildlife Comments on CCAA (158 KB)

2008 John Muir Institute Comments on CCAA (34 KB)

2008 FWS Final Environmental Action Statement Screening for Candidate Conservation Agreement with Assurances (CCAA) (75 KB)

Zielinksi, W.J. 2007. Comments on Feasibility Review. (26 KB)

Fisher Listing

2014 Federal Notice to list the West Coast Distinct Population Segment of the fisher as a threatened species under the Federal Endangered Species Act (796 KB PDF)

2010 March California State Status Review for Fisher Listing under CESA (5.47 MB)

2010 60-Day Notice of Intent under Federal Endangered Species Act (22 KB)

2008 Petition to List the Pacific fisher under California ESA (972 KB)

2004 U.S. Fish and Wildlife Service Decision not to list Pacific fisher (210KB PDF)

2003 U.S. FWS Merit Ruling for Status Review of Pacific fisher (58KB PDF)

2003 Court Decision Calling on U.S. FWS to Examine Listing the Pacific fisher (752KB PDF)

2000 Petition to list as Endangered Species (963KB PDF)

More Natural History -- Off site

Conservation Biology Institute - Southern Sierra Nevada Fisher Assessment

SNAMP (Sierra Nevada Adaptive Management) fisher website

California Department of Fish and Game Natural History Information --This California state website contains rather limited and old information but is a good basic background composite for the species. Choose from a drop-down list to select the animal you are interested in.