USDA Forest Service

Pacific Southwest Research Station
Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
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Research Topics Ecosystem Processes

Sierra Nevada Ecosystems

Links between landscape condition and survival and reproduction of fishers in the Kings River Area of the Sierra National Forest

Study Plan

The Research

Fishers in California have experienced a substantial reduction in geographic range and currently occur as two populations separated by over 400 km (240 miles). As a result of this fragmentation, the fisher is considered a California species of concern, a USFS sensitive species, and its listing under the Endangered Species Act has been ruled by the USFWS as warranted but precluded. The southern Sierra Nevada population is of particular concern because of its geographic and genetic isolation, its risk of catastrophic decline, its unique ecological nature, and the unknown impact of proposed forest management actions.

The goal of the Kings River Project is to use uneven-aged silviculture and prescribed fire to move forest structure and composition across the greater part of two watersheds toward a desired condition estimated to be similar to pre-1850 forest conditions prior to fire suppression. Specific objectives are to reduce fire risk near human developments, establish a sustainable level of timber products through forest thinning and planting, reduce the potential for catastrophic habitat loss to insects and wildfire, and provide opportunities for scientific study of treatment effects.

Large-scale landscape manipulations such as the Kings River Project provide an opportunity to understand the impacts of landscape change resulting from forest management practices on this secretive, wide-ranging carnivore. By monitoring fisher population dynamics before, during, and after the treatments, and concurrently monitoring untreated areas, we can identify both the direct and indirect effects of treatments. These data can then be used to generate spatially-explicit population models which can be used to perform additional ‘virtual’ experiments and provide predictive power to land managers.


blue arrrowCollect sufficient autoecological data to quantify fisher population vital rates in the Kings River Project. Combine these rates with landscape-level habitat data in a spatially-explicit, process-based population model to identify limiting factors.
blue arrrowExamine the habitat use of fishers at both the landscape and within-territory scale. What types of areas within home ranges receive disproportionately greater and lesser use?
blue arrrow Capitalize on the proposed Kings River fuel treatments in a landscape-level, before/after-control/impact experiment to illuminate the impacts of USFS management options on fishers. Do fuel treatments result in increased physiological stress and/or reduced reproductive output? Is there significant avoidance of areas that are mechanically thinned or burned? If so, for how long after treatment does this behavior persist?
blue arrrowDocument the pathology/serology of the southern Sierran fisher population. Have they been exposed to disease or parasites that might threaten the population or are they naïve to specific pathogens that could become a threat if fishers are translocated into the Sierras from other populations?
blue arrrowMirror the University of California , Sierra Nevada Adaptive Management project such that the two studies can be considered pseudo-replicates of a large-scale study to examine the overall effects of landscape heterogeneity on fishers

Methods and Design

To maximize the information available, the Kings River fisher program consists of three complementary methods in a nested design. Detailed survival, reproduction, and habitat use data are being collected via live-capture and radio-telemetry, with a goal of maintaining 20 animals on the air at any time. Camera surveys will be used to estimate population density, identify uncollared animals, and document the overall carnivore community. Finally, scat detector dogs from the University of Washington (UW) Center  for Conservation Biology are being used to survey for fishers across the entire Kings River Administrative Area twice each year. Genetic analysis performed at the USFS Rocky Mountain Wildlife Genetics Laboratory will link samples collected via trapping with those collected by detector dogs. Hormone analysis conducted at UW will provide a sensitive evaluation of the effects of fuel treatment activities on fisher reproduction, nutritional status, and stress levels. Dietary analysis, conducted at the USFS Redwood Sciences Laboratory, will illuminate how treatments impact fisher resource use. Finally, this nested design will facilitate the comparison of detector dog surveys with more traditional telemetry monitoring, and over time may reduce our reliance on invasive monitoring techniques.

Application of Research Results

The Kings River Sustainable Forest Ecosystem Project was initiated in the Sierra National Forest in 1994. This collaborative adaptive management project was designed to investigate relationships between forest ecosystems in the southern Sierra Nevada managed to mimic processes that shaped historic forests and an array of ecosystem elements in a scientifically structured manner. The project provides a unique opportunity to meet existing information needs for conservation planning for fishers because silvicultural treatments and prescribed fire will be implemented on a landscape scale within the current limited distribution of fishers in the Sierra Nevada .

Current plans for managing National Forest System lands need to consider requirements of fishers and fisher habitat and address these needs in their environmental analyses. Results from this study will allow us to examine population trends, factors limiting fisher populations in the southern Sierra Nevada , the potential impact of management decisions on fishers, and the potential to repopulate areas of the Sierra Nevada in which fishers are currently absent. This study will a ssess fisher response to ongoing and proposed management activities and provide information crucial to understanding how we can maintain fisher population viability while reducing wildfire risk. The improved understanding of fisher ecology that will result from this work will lead to more informed management decisions and increased ability to satisfy National Forest Management Act and Sierra Nevada Forest Plan Amendment EIS obligations for viable, well-distributed fisher populations.

map of the Sierra Nevada Ecoregion

The study centers on the Kings River Administrative Area and encompasses approximately 100,000 acres of the Sierra National Forest in the Southern Sierra Nevada . It covers an elevational gradient corresponding to fisher occurrence, roughly 1066 – 2286 meters (roughly 3500’-7500’), and includes ponderosa pine, hardwood, and mixed conifer habitat.

Lead Scientists/Collaborators

1) Purcell, Kathryn; 1) Thompson, Craig

1) USDA Forest Service,
Pacific Southwest Research Station
Sierra Nevada Research Center
2081 E. Sierra Ave.
Fresno, CA 93710
ph: 559-868-5283
fax: 559-297-3355

University of California , Sierra Nevada Adaptive Management Program – SNAMP is a comprehensive approach to understanding the impacts of fuel management on forest ecosystems. Collaboration will allow both studies to be considered pseudo-replicates of a regional research program.

University of Washington Center for Conservation Biology – CBC biologists are developing non-invasive methods for large-scale population monitoring.

USFS Rocky Mountain Research Station – RMRS is involved in a number of fisher research programs including spearheading an effort to use genetic data to uncover barriers to fisher dispersal in the Sierras.

UC Davis – UCD School of Medicine and Epidemiology is currently conducting a state-wide mesocarnivore disease assessment, and collaboration will help determine the exposure history of Sierran fishers and any risk posed by translocation efforts.

USFS Redwood Sciences Lab

Fresno-Chaffee Zoo

CSU Fresno

Last Modified: Aug 29, 2016 10:56:35 AM