Snake River Sockeye Salmon Captive Broodstock; Research Element, 1993 Annual Report.

Abstract

In 1991, the National Marine Fisheries Service listed Snake River sockeye salmon Oncorhynchus nerka as endangered under the Endangered Species Act of 1973. Initial steps to recover the species include the establishment of captive broodstocks at the Eagle Fish Hatchery in Eagle, Idaho. Research and recovery activities for sockeye conducted by the Idaho Department of Fish and Game during the period of April 1993 to April 1994 are covered by this report. Eight anadromous adults (two female and six male) returned to the Redfish Lake Creek trap this year and were spawned at the Sawtooth Hatchery near Stanley, Idaho. Fecundity was 3160 for each female. The mean fertilization rate was 52% for female {open_quotes}A{close_quotes} and 65% for female {open_quotes}B.{close_quotes} Captive broodstock also spawned as well as residual sockeye captured in a Merwin trap in Redfish Lake. Spawning data from 72 fish spawned during this period is included in this report. Captive broodstock also matured later than normal (winter and spring 1994). Fish were spawned and samples were taken to investigate reasons for poor fertilization rates. Twenty-four out migrants of 1991 were selected for return to Redfish Lake for volitional spawning. Releases were made in August of 1993. All fish were implanted with sonic tags and tracking of this group began soon after the release to identify spawning-related activities. A research project is being conducted on captive broodstock diets. The project will investigate the effect of diet modification on spawn timing, gamete quality, and fertilization rates. A second project used ultrasound to examine fish for sexual maturity. The goal was to obtain a group a fish to be released f or volitional spawning. A total of 44 fish were found to be mature. The performance of all captive groups held at Eagle are included in this report.