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<br />565 <br /> <br />NON-NATIVE SPECIES INTERACTIONS <br />1997 Work Plan <br />U.S. Fish and Wildlife Service, Region 2 <br /> <br />Background: <br /> <br />Introduced species have been implicated in the decline of several native fishes. In the Colorado River <br />drainage, introductions occurred simultaneously with flow-related habitat alterations. These events <br />coincided with a basinwide decline in distribution and abundance of many native species, in particular <br />the Colorado squawfish and razorback sucker. <br /> <br />Various laboratory and field studies have described the interactions among native and non-native <br />species. Impacts on native fishes include resource overlap in both diet and habitat use (i.e., potential <br />competition), predation, and hybridization. <br /> <br />There are non-native species that are potential predators of adult and juvenile native fishes in the San <br />Juan River; the most important numerically is the channel catfish. The red shiner is a common, <br />exotic, potential predator oflarval native fish. Non-native species that are potential competitors of <br />natives are numerically dominated by common carp, red shiner, and fathead minnow. The introduced <br />white sucker hybridizes and may also compete with native flannelmouth sucker. <br /> <br />This component of the San Juan River research addresses the impacts of non-native species on native <br />fishes. Research include_s the effects of predation by non-native species on various life stages of <br />native fishes, the commonality of resource use between native and non-native fish species, and the <br />relation of these findings to differing flow regimes. <br /> <br />A radio telemetry study of channel catfish was initiated in 1996 to determine seasonal movement <br />patterns related to habitat use and reproductive activities. Prior mark-recapture data of channel <br />catfish during this study indicated limited movement. Most literature, however, generally recognize <br />seasonal movement for reproductive purposes. Because of probable inherent difficulties in the <br />recapture of tagged fish (Le., frequency of collection efforts, chance of recapture) previous efforts <br />have not identified such movements. The radio telemetry study of channel catfish will allow for <br />greater definition of not only general movement patterns, but aspects regarding habitat use and <br />relationship to rare native species habitat use patterns. This study will also allow for collection of <br />data related to winter low-flow studies. The purpose of this research ultimately is to provide <br />flow/management recommendations that will reduce the abundance of non-natives in the San Juan <br />River. <br /> <br />Objectives: <br /> <br />1. Determine seasonal movement patterns and habitat use of channel catfish in relation <br />to flow patterns in the San Juan River. <br />2. Validate channel catfish movement data collected using Floy tags_ <br />3. Determine food habits and food availability of native and non-native fishes in <br />backwaters and secondary channels and evaluate for dietary overlap. <br /> <br />25 <br />