Snake River Sockeye Salmon Captive Broodstock Program; Research Element, 2001 Annual Report.

Abstract

On November 20, 1991, the National Marine Fisheries Service listed Snake River sockeye salmon Oncorhynchus nerka as endangered under the Endangered Species Act of 1973. In 1991, the Shoshone-Bannock Tribes and Idaho Department of Fish and Game initiated the Snake River Sockeye Salmon Sawtooth Valley Project to conserve and rebuild populations in Idaho. Restoration efforts are focusing on Redfish, Pettit, and Alturas lakes within the Sawtooth Valley. The first release of hatchery-produced juvenile sockeye salmon from the captive broodstock program occurred in 1994. The first anadromous adult returns from the captive broodstock program were recorded in 1999, when six jacks and one jill were captured at Idaho Department of Fish and Game's Sawtooth Fish Hatchery. In 2001, progeny from the captive broodstock program were released using four strategies: age-0 presmolts were released to all three lakes in October and to Pettit and Alturas lakes in July; age-1 smolts were released to Redfish Lake Creek, and hatchery-produced adult sockeye salmon were released to Redfish Lake for volitional spawning in September along with anadromous adult sockeye salmon that returned to the Sawtooth basin and were not incorporated into the captive broodstock program. Kokanee population monitoring was conducted on Redfish, Alturas, and Pettit lakes using a midwater trawl in September. Only age-0 and age-1 kokanee were captured on Redfish Lake, resulting in a population estimate of 12,980 kokanee. This was the second lowest kokanee abundance estimated since 1990. On Alturas Lake age-0, age-1, and age-2 kokanee were captured, and the kokanee population was estimated at 70,159. This is a mid range kokanee population estimate for Alturas Lake, which has been sampled yearly since 1990. On Pettit Lake only age-1 kokanee were captured, and the kokanee population estimate was 16,931. This estimate is in the midrange of estimates of the kokanee population in Pettit Lake, which has been sampled yearly since 1992. We continue to have difficulty capturing age-0 kokanee in the midwater trawl on Pettit Lake. Angler surveys were conducted on Redfish and Alturas lakes to estimate kokanee harvest and to estimate return to creel for hatchery rainbow trout planted in Alturas Lake. We failed to encounter any kokanee that had been harvested in 88 angler interviews conducted between May 26 and August 7, resulting in an estimated kokanee harvest of zero. On Alturas Lake, we again failed to encounter any harvested kokanee in 116 angler interviews, resulting in an estimated kokanee harvest of zero. We estimated that anglers harvested 9.5% of the 6,598 rainbow trout planted in Alturas Lake. We estimated that 110 wild/natural and 9,616 hatchery-produced sockeye salmon smolts out-migrated from Redfish Lake in 2001. This was the lowest estimate of unmarked smolt out-migration since monitoring began in 1991. The trap on Redfish Lake Creek was operated from April 22 to June 6, 2001 to estimate out-migration. Mean travel times for PIT-tagged smolts from Redfish Lake Creek Trap to Lower Granite Dam was 10.3 days for wild/natural smolts and 10.6 days for hatchery-produced smolts. Based on cumulative unique PIT tag interrogations from Sawtooth basin traps to mainstem Snake and Columbia river dams, the Redfish Lake wild/natural smolts, Redfish fall direct presmolts group, and Alturas Lake fall direct presmolts recorded the highest detection rates. In 2001, 65 hatchery-raised and 14 anadromous adult sockeye salmon were released to Redfish Lake for natural spawning. We observed 12 to 15 areas of excavation in the lake that were possible redds. We monitored bull trout spawning on Fishhook Creek, a tributary to Redfish Lake, and on Alpine Creek, a tributary to Alturas Lake. This represented the fourth consecutive year that the index reaches have been surveyed on these two streams. Adult counts on Fishhook Creek were similar to previous years as were redd counts. On Alpine Creek, bull trout numbers were also similar to previous years, but the number of redds observed increased over previous years. We noted that redds counted during the first survey could become obscured before the final survey, indicating that the counts were not cumulative. We recommend marking redds during the first survey so that a total count can be obtained.