Migration Timing and Survival to Bonneville Dam of Juvenile Spring Chinook Salmon in the Deschutes Basin. Report for Migration Year 2010 (Brood Year 2008)

摘要

A total of 14,907 Warm Springs NFH and 7,454 Round Butte hatchery brood year 2008 spring Chinook salmon juveniles were PIT tagged as part of a Deschutes basin spring Chinook salmon monitoring and evaluation program. At Warm Springs NFH, PIT tags were split into two raceways, raceway 21 which had a volitional release of juveniles between March 24 and April 21 of 2010, and raceway 29 which had an abbreviated volitional release between March 24 and March 29 of 2010. Round Butte juveniles were volitionally released between April 13 and June 3 of 2010. PIT tag antenna arrays were constructed to monitor the release of juveniles from each facility. The majority of Round Butte juveniles left their holding facility in the first three days of the volitional release, while the Warm Springs juveniles migrated out in a more variable pattern. Round Butte juveniles migrated downstream to Bonneville Dam the fastest, with a median migration time of 12.5 days, compared to 25 days for Warm Springs NFH raceway 21 juveniles and 33 days for Warm Springs NFH raceway 29 juveniles. Median day of passage of PIT tagged juveniles over Bonneville Dam was April 26 for Round Butte juveniles, May 2 for Warm Springs NFH juveniles from raceway 21, and May 4 for Warm Springs NFH juveniles from raceway 29. Estimated survival from release to Bonneville Dam was similar for juveniles from each raceway at Warm Springs NFH, with a combined survival estimate of 57% (95% C.I. of 48%-66%). Estimated survival of Round Butte juveniles was 73% (95% C.I. of 58% to 84%). No statistical difference in survival between the Warm Springs NFH and Round Butte hatchery stocks was observed. Of the PIT tagged juveniles detected leaving each facility, 352 Warm Springs NFH tags and 239 Round Butte hatchery tags were recovered on the bird colonies on East Sand Island in the lower Columbia River in 2010. Differences in size at release and release timing may have influenced the migration characteristics and survival of juveniles from the two hatcheries. Size at release differed between the two hatcheries, with Warm Springs NFH releasing fish at approximately 20 fish/lb and Round Butte releasing fish at 9.5 fish/lb. At Warm Springs NFH, juveniles that were released the earliest (raceway 29) had the slowest migration time to Bonneville Dam, while Round Butte juveniles had the fastest migration time. Mini-jacking rates differed between the two hatchery stocks, with 32 PIT tagged Round Butte mini-jacks detected at Bonneville Dam compared to three Warm Springs NFH mini-jacks. Adult age structure and return rates will be monitored for each stock.