Comparison of the Distribution and Recapture Rates of Acclimated and Nonacclimated Razorback Sucker Stocked into the Green River
Timothy Modde, Garn J. Birchell, and Kevin D. Christopherson
Abstract.—As part of an upper Colorado River basin recovery effort, razorback sucker Xyrauchen texanus augmentation will increase significantly in the coming years. In an effort to examine efficiency, we compared the capture returns of acclimated and nonacclimated razorback sucker in the middle Green River. We compared riverine recapture rates of fingerling razorback sucker reared for one growing season in offchannel wetlands, that accessed the river voluntarily as subadults, with subadult fish (>250 mm total length) stocked directly in the Green River from the Ouray National Fish Hatchery. This presentation summarizes the capture returns of fish acclimated in wetlands for an entire growing season with those stocked directly from the hatchery.
The distribution and recapture rates of approximately 2,000 subadult/adult razorback sucker (>250 mm) stocked directly into the river between 1997 and 2001 were compared with approximately 2,192 acclimated fish that accessed the Green River from offchannel wetlands. The entire reach of the Green River between Split Mountain Canyon (river kilometer [rk] 516) and the confluence (rk 0) with the Colorado River was sampled with electro-fishing boats during the spring of 2001. As expected, the majority of poststocking movement occurred downstream of the stocking site. Little difference in observed catch rates and distribution occurred between acclimated and nonacclimated razorback sucker. However, it is probable that the total number of acclimated fish was underestimated and higher survival probably occurred within acclimated fishes. In addition, long-term survival of nonacclimated fishes remains questionable.