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Spatial Analyses to Evaluate Threats to Critical Habitat for Endangered Colorado River Fishes

Spatial Analyses to Evaluate Threats to Critical Habitat for Endangered Colorado River Fishes


Project Dates: July 2001 - December 2002

Funding Sponsor: Colorado Division of Wildlife

Principal Investigator: Nathan Nibbelink

Project Summary:

Nonnative fish species are suspected of having a significant negative impact on the current status and recovery potential of the Colorado River endangered fishes. Ultimately, the goal of this project was to evaluate the effectiveness of Coloradoâ€TMs fish stocking regulations in achieving the desired biological responses of fish communities within critical habitat for endangered fishes. Primary objectives were: (1) To determine if the administration of fish stocking regulations and permits is contributing to the reduction in riverine abundance of target nonnative fish species. (2) To monitor the trend in distribution and abundance indices for target nonnative fish species in riverine habitats, and compare the indices to concurrent public/private fish stocking data. (3) To conduct a risk analysis (RAMC 1996) of nonnative fish stocking in the UCRB in Colorado to identify its relative significance and potential for introducing nonnative fish species into critical habitat for endangered fishes. We used spatial pattern analyses to evaluate linkages between abundance of non-native fishes in riverine critical habitat relative to densities seen/or stocked in floodplain ponds. The primary finding was that once in riverine habitat, almost universally, non-native fishes are prolific in their spatial distribution. This suggests that a finer-grained analysis of the connectivity of waters that may be sources of non-natives is called for, as spatial relations alone cannot isolate problem locations.


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