Southern Sierra Nevada Fisher Assessment
The Pacific fisher (Martes pennanti) is a large member of the weasel family associated with dense, structurally complex, low- to mid-elevation forests in California and Oregon. Remaining populations are small, disconnected from one another, and threatened by habitat modification and fragmentation. In 2004, the U.S. Fish and Wildlife Service found that Pacific fishers were warranted protection under the Endangered Species Act, but that listing the species was precluded by higher priorities. (June 2008)
Project Description
The fisher (Martes pennanti) is a large member of the weasel family associated with dense, structurally complex, low- to mid-elevation forests. Remaining populations in the western U.S. are small, disconnected from one another, and threatened by habitat modification and fragmentation. In 2004, the U.S. Fish and Wildlife Service found that the west coast distinct population segment of the fisher was warranted protection under the Endangered Species Act, but that listing the species was precluded by higher priorities.
In the Sierra Nevada, fishers currently occupy less than half their historic range, having apparently been extirpated from the central and northern Sierra. A small population persists in the southern Sierras, south from Yosemite National Park to the vicinity of the Greenhorn Mountains in southern Tulare County.
Forces that can reduce habitat value for fishers range from stand-replacing wildfires to management actions intended to preclude such fires by reducing the amount and continuity of forest fuels. 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 Sierran fisher population and how it is likely to change in the future. The Conservation Biology Institute (CBI) has therefore been commissioned by Region 5 of the U.S. Forest Service to compile all available data on fisher populations and habitat in the southern Sierra Nevada, assess their current status, and predict how they are likely to respond to various alternative forest management actions, as well as unmanaged events such as wildfires, drought, or bark beetle outbreaks. The project is designed to create a scientifically credible set of habitat maps and estimates of fisher population size and distribution in the southern Sierra Nevada based on current conditions. Then, using spatial modeling methods, we will assess how fisher habitat and populations are likely to change in the future under a range of alternative scenarios.
The project involves extensive collaboration with other scientists, stakeholders, and agencies. A group of independent science advisors has been assembled to oversee all technical aspects of the analyses and ensure use of best available science. The advisors were chosen for their expertise in fisher biology, forest ecology, silviculture, fire management, landscape dynamics modeling, and population viability assessment. Stakeholder groups are kept informed via a group of stakeholder representatives comprising individuals from the timber industry, conservation organizations, the U.S. Fish and Wildlife Service, California Department of Fish and Game, and the various National Parks and Forests in the study area. Finally, although CBI’s work products are produced independent of the U.S. Forest Service to ensure objectivity, we collaborate closely with various experts from the Pacific Southwest Research Station and Region 5 to obtain and interpret data and to ensure that our analyses accurately reflect how proposed forest management actions are likely to affect habitat conditions on the ground.
This website is intended to keep all interested parties informed throughout the course of this project.
June 2008
