Survival of Razorback Sucker Stocked into the Lower Colorado River, Final Project Report, October 2004-December 2005

摘要

Portions of the lower Colorado River, Parker Dam to Imperial Dam, were surveyed during the period October 2004 to December 2005 for presence of razorback sucker Xyrauchen texanus. The study area primarily encompassed areas of known razorback sucker occupation including the main river channel and confluent, watercraft-accessible backwaters and side channels in the counties of La Paz and Yuma, Arizona, and San Bernardino, Riverside, and Imperial, California. Methods were boat electrofishing, trammel netting, and hoop netting that resulted in contact with a total of 31,122 fish representing at least 22 species and including 654 razorback sucker encounters; 2.1% of the total catch. These encounters represent 592 individual fish, all of which are thought to have been repatriated. Five hundred fish were PIT tagged by ASU during the study period and 92 were tagged prior to the study period or prior to stocking. Mean total length was 37.7 cm (range 27.6 54.0). Sex ratios were 100 female, 169 male, 277 juvenile, and 46 unknown. Razorback sucker recapture occurrences have been sufficient for mark-recapture analysis and population estimation for three lower Colorado River backwaters.