Abstract

The cutthroat trout currently inhabits only a small portion of its historic range. While numerous factors caused the decline, movement barriers, either physical, in the form of anthropogenic alterations to the landscape (e.g. livestock grazing, highway culverts, dams and water diversions), chemical (e.g. increased water temperatures), or biotic (e.g. non-native salmonids) prevent populations from exchanging individuals and colonizing new areas. Barriers and associated habitat fragmentation limit many extant populations to stream fragments of insufficient length to provide long-term population viability. The proposed research will identify landscape variables associated with cutthroat trout presence/absence, identify landscape variables allowing persistence in the face of invasions by non-native salmonids, identify the best areas and configurations for coldwater stream conservation reserves, and identify candidate areas for restoration. Applications of this research will benefit native salmonids and other aquatic species with similar requirements on Nature Conservancy sites and elsewhere throughout the United States."

From the introduction: "Researchers have collected much information in recent years about the status, life history, and habitat relationships of the various subspecies of cutthroat trout. However, we know little about mechanisms determining regional patterns of cutthroat trout distribution and abundance. The spatial scale of prior and ongoing research is typically restricted to a single stream or stream segment. However, by assembling existing studies and surveys into a large database, we may identify large scale, regional patterns and the factors that determine cutthroat trout distributions. This information will allow identification of populations most at risk, identify the best possible candidate streams for population restoration, and identify the best areas in which to establish conservation reserves. The proposed research seeks to answer three central questions: 1) Can cutthroat trout distributions be predicted from upslope, landscape level variables such as parent geology, road density, and vegetation type, and can variables be identified allowing these fish to withstand invasions of non-native salmonids? Similarly, 2) Can general instream habitat characteristics be predicted from the landscape setting? This information will be used in a matrix-based demographic model incorporating current and potential populations, landscape features, disturbance regime, fish mobility, and known barriers to answer question 3) Can we identify areas (coldwater conservation reserves) where populations will most likely resist extinction?