Snake River Sockeye Salmon Captive Broodstock Program; Research Element, 2003 Annual Report.

Abstract

On November 20, 1991, the National Oceanic Atmospheric Administration listed Snake River sockeye salmon Oncorhynchus nerka as endangered under the Endangered Species Act of 1973. In 1991, the Shoshone-Bannock Tribes (SBT) and Idaho Department of Fish and Game (IDFG) initiated the Snake River Sockeye Salmon Captive Broodstock Program to conserve and rebuild populations in Idaho. Restoration efforts are focused on Redfish, Pettit, and Alturas lakes within the Sawtooth Valley. The first release of hatchery-produced adults occurred in 1993. The first release of juvenile sockeye salmon from the captive broodstock program occurred in 1994. In 1999, the first anadromous adult returns from the captive broodstock program were recorded when six jacks and one jill were captured at the IDFG Sawtooth Fish Hatchery. In 2003, progeny from the captive broodstock program were released using three strategies: eyed-eggs were planted in Pettit and Alturas lakes in November and December, age-0 presmolts were released to Alturas, Pettit, and Redfish lakes in October, and hatchery-produced adult sockeye salmon were released to Redfish Lake for volitional spawning in September. Oncorhynchus nerka population monitoring was conducted on Redfish, Alturas, and Pettit lakes using a midwater trawl in September 2003. Age-0 through age-4 O. nerka were captured inmore » Redfish Lake, and population abundance was estimated at 81,727 fish. Age-0 through age-3 O. nerka were captured in Alturas Lake, and population abundance was estimated at 46,234 fish. Age-0 through age-3 O. nerka were captured in Pettit Lake, and population abundance was estimated at 11,961 fish. Angler surveys were conducted from May 25 through August 7, 2003 on Redfish Lake to estimate kokanee harvest. On Redfish Lake, we interviewed 179 anglers and estimated that 424 kokanee were harvested. The calculated kokanee catch rate was 0.09 fish/hour. The juvenile out-migrant trap on Redfish Lake Creek was operated from April 15 to May 29, 2003. We estimated that 4,637 wild/natural and 12,226 hatchery-produced sockeye salmon smolts out-migrated from Redfish Lake in 2003. The hatchery-produced component included an estimated 5,352 out-migrants produced from a summer direct-release made to Redfish Lake in 2002 and 6,874 out-migrants produced from a fall direct-release made in 2002. The juvenile out-migrant traps on Alturas Lake Creek and Pettit Lake Creek were operated by the SBT from April 23 to June 5, 2003 and April 25 to June 4, 2003, respectively. The SBT enumerated 28 wild/natural and 13,329 hatchery-produced sockeye salmon smolts that outmigrated from Pettit Lake and estimated 286 wild/natural and 553 hatchery-produced sockeye salmon smolts out-migrated from Alturas Lake in 2003. The hatchery-produced component of sockeye salmon out-migrants originated from presmolt releases made directly to Pettit and Alturas lakes in 2002. Median travel times for passive integrated transponder (PIT) tagged smolts from the Redfish Lake Creek trap site to Lower Granite Dam were estimated for wild/natural smolts and hatchery-produced smolts. Median travel times for smolts originating from the Redfish Lake Creek trap were 10.6 d for wild/natural smolts, 6.2 d for summer direct-released smolts, and 7.1 d for fall direct-released smolts. Median travel times for PIT-tagged smolts from the Pettit Lake Creek trap site to Lower Granite Dam were estimated for hatchery-produced smolts. Median travel times for smolts originating from the Pettit Lake Creek trap were 14.1 d for fall direct released smolts and 13.6 d for fall direct released smolts. Cumulative unique PIT tag interrogations from Sawtooth Valley juvenile out-migrant traps to mainstem Snake and Columbia river dams were utilized to estimate detection rates for out-migrating sockeye salmon smolts. Detection rate comparisons were made between smolts originating from Redfish, Alturas, and Pettit lakes and the various release strategies. Pettit Lake fall direct released smolts recorded the highest detection rate of 37.14%. In 2003, 312 hatchery-produced adult sockeye salmon were released to Redfish Lake for natural spawning. We observed 42 areas of excavation in the lake from spawning events. Suspected redds were approximately 3 m x 3 m in size and were constructed by multiple pairs of adults. We monitored bull trout spawning in Fishhook Creek, a tributary to Redfish Lake, and in Alpine Creek, a tributary to Alturas Lake. This represented the sixth consecutive year that the index reaches have been surveyed on these two streams. Adult counts (40 adults) and redd counts (17 redds) in Fishhook Creek were similar to counts conducted since monitoring began in 1998. Bull trout numbers (27 adults) and the number of redds observed (14 redds) have gradually increased in Alpine Creek compared to counts from initial monitoring.« less