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<br />catch per unit effort is too variable for detecting population trend. However, if the study area is <br /> <br /> <br />expanded to a larger geographical area (i.e., Whirlpool, Split Mountain and Lodore canyons) that <br /> <br /> <br />includes other adult populations, the resulting combined populations may result in increased <br /> <br /> <br />numbers of captures and recaptures and, furthermore, increase the probability of recapturing fish <br /> <br />marked in Yampa Canyon but that may have moved to these adjacent areas, thus making a <br /> <br />precise and unbiased population estimate more feasible. We recommend a three year three pass <br /> <br />electrofishing capture-recapture study in this expanded geographical area, combined with seining <br /> <br />to monitor reproductive success. <br /> <br />Conclusions <br /> <br />Using a three pass capture-recapture method, insufficient numbers of marked fish were <br /> <br />captured to produce a reasonable (bias < 10%, CV < 0.2) population estimate. Given that <br /> <br />humpback chub in Yampa Canyon have been documented (Miller and Modde, 1999) to travel <br /> <br />long distances relative to other humpback chub populations, we are unsure if the inability to <br /> <br />recapture sufficient numbers of humpback chub is due to their movement to habitats outside of <br /> <br />Yampa Canyon (e.g., Whirlpool, Lodore , and Split Mountain canyons), mortality of tagged fish, <br />or inefficiency of our capture methods. <br /> <br />Recommendations <br /> <br />1. Yampa Canyon represents marginal habitat for humpback chub during the base flow period, <br /> <br />16 <br />