Consideration of extinction risks for salmonids /

Abstract

Under the National Forest Management Act of 1979, the USDA Forest Service is charged with maintaining viable populations of all existing native vertebrate species on lands they administer. Accomplishment of this responsibility requires complete assessment of all federally authorized, funded, or implemented projects that may jeopardize the continued existence of a species. An understanding of the processes of extinction and the characteristics of populations that make them more or less likely to persist is fundamental to such assessments. We review processes contributing to extinction and characterize them as deterministic , stochastic , and genetic. Factors that strongly influence risks of local and regional extinction include replication, dispersal and connection among populations representing a regional metapopulation. Project planning and assessments must address habitat disruption and population responses at both the local and regional scale. Maintaining strong populations in the best possible habitats throughout the landscape and preserving the ecological processes characteristic of metapopulations are the best hedges against extinction.^% MSS & ' on :ti d ,8 1 d3S USDAsy Forest Service AJiVHSTI 3IH3V l.iV.i vosn FHR Currents Purpose The USDA Forest Service Fish Habitat Relationships Program was established to further the development of fisheries technology and transfer this technology to field biologists. With ever increasing demands for natural resources, protection and management of aquatic communities requires biologists to be knowledgable of current research findings and state-of-the-art techniques. The purpose of Intermountain/Northern Region

A Critique of the Recovery of Greenback Cutthroat Trout

“…To avoid this criticism, the recovery plan for greenback cutthroat trout should include an explicit biological rationale for the delisting goal of 20 stable populations, as should goals specified in other salmonid recovery plans (e.g., USFWS 1993, 1995; ATLCRSRT 2000. A related concern is that only one of these plans ( USFWS 1995) acknowledges temporal concerns, such as the probability of population persistence for a specified period as a consequence of variation in genetic, demographic, or environmental factors ( Rieman et al 1993); thus, most plans probably underestimate species' extinction risks.…”

“…Unquestionably, the risk of extinction of greenback cutthroat trout has declined since 1957. But most remnant and recently introduced populations of greenback cutthroat trout are characteristic of populations at moderate to extreme risk of extinction, because they inhabit waters that are small, isolated, unproductive, and in close proximity ( Rieman et al 1993; Young 1995) and represent populations at risk of extirpation by natural events (cf. USFWS 1998 c .…”

Migration, Size, and Age Structure of Brook Trout (Salvelinus fontinalis) from Two Lake Superior Tributaries

“…In the context of evolution, such intraspecific diversity is a means for a species to colonize or recolonize habitat patches after disturbance (Northcote, 1992). Conserving the biodiversity of a species has the potential to make it more robust to both natural and anthropogenic disturbance on a variety of scales (Rieman et al, 1993;Worm et al, 2006;Schindler et al, 2010). Conversely, the loss of a life history could make a species more susceptible to climate change related disturbance and anthropogenic impacts.…”

Persistence of Colorado River Cutthroat Trout Populations in Isolated Headwater Streams of Wyoming

“…Although barriers provide protection from invasion by nonnative species, isolation has its own risks (Peterson et al 2008;Fausch et al 2009). When immigration is blocked by barriers, isolated populations may be vulnerable to extinction because of stochastic demographic or environmental events (Rieman et al 1991;Hilderbrand 2003). Isolation also results in reduced gene flow and genetic variation, increasing the risk of inbreeding depression and reducing evolutionary potential (Allendorf and Ryman 2002).…”

“…Once a population is small enough that declines cause genetic bottlenecking, reduced fitness due to genetic factors can lead to further declines. The combined effects of low genetic variation, environmental stressors, and catastrophic events are hypothesized to lead to negative Transactions of the American Fisheries Society 139: [1500][1501][1502][1503][1504][1505][1506][1507][1508][1509][1510]2010 Ó Copyright by the American Fisheries Society 2010 DOI: 10.1577/T09-133.1 [Article] population growth rates, a phenomenon that has been described as an ''extinction vortex'' (Gilpin and Soulé 1986;Rieman et al 1991). For isolated cutthroat trout populations, demographic support from nearby populations is not available and negative population growth is a sign that a population may not persist (Peterson et al 2008).…”