Tucannon River Spring Chinook Salmon Hatchery Evaluation Program: 2007 Annual Report

Lyons Ferry Hatchery (LFH) and Tucannon Fish Hatchery (TFH) were built/modified under the Lower Snake River Fish and Wildlife Compensation Plan. One objective of the Plan is to compensate for the estimated annual loss of 1,152-spring Chinook (Tucannon River stock) caused by hydroelectric projects on the Snake River. The conventional supplementation production goal was revised in 2006 to 225,000 fish for release as yearlings at 30 g/fish (15 fish per pound). The captive brood production goal is 150,000 yearlings at 30 g/fish. This report summarizes activities of the Washington Department of Fish and Wildlife Lower Snake River Hatchery Evaluation Program for Tucannon River spring Chinook for the period April 2007 to April 2008.

Two hundred twenty-four salmon were captured in the TFH trap in 2007 (98 natural adults, 14 natural jacks, 53 hatchery adults, and 59 hatchery jacks); 88 were collected and hauled to LFH for broodstock and the remaining fish were passed upstream. During 2007, five salmon that were collected for broodstock died prior to spawning.

Spawning of supplementation fish in 2007 at LFH occurred between 28 August and 18 September, with a peak eggtake occurring on 18 September. A total of 124,543 eggs were collected from 27 natural and 9 hatchery-origin fish. Egg mortality to eye-up was 3.9% (4,953 eggs), with an additional loss of 2,408 (2.0%) sac-fry. Total fry ponded for production in the rearing ponds was 117,182.

WDFW staff conducted spawning ground surveys in the Tucannon River between 29 August and 27 September, 2007. Thirty-two redds and 14 carcasses were found above the adult trap and 49 redds and 44 carcasses were found below the trap. Based on redd counts, broodstock collection, and in-river pre-spawning mortalities, the estimated escapement for 2007 was 344 fish (190 natural adults, 8 natural jacks and 113 hatchery-origin adults, 33 hatchery jacks).

Evaluation staff operated a downstream migrant trap to provide juvenile outmigration estimates. During the 2006/2007 emigration, we estimated that 17,579 (BY 2005) natural spring Chinook smolts emigrated from the Tucannon River.

Monitoring survival rate differences between natural and hatchery-reared salmon continues. Smolt-to-adult return rates (SAR) for natural salmon consistently average about five times higher than for hatchery salmon. However, hatchery salmon survive about three times greater than natural salmon from parent to adult progeny. Due to the low SAR for hatchery fish, the mitigation goal of 1,152 salmon of Tucannon River stock was not achieved as only 146 hatcheryorigin fish returned in 2007. Beginning with the 2006 brood year, the annual smolt goal was increased from 132,000 to 225,000 to help offset the higher mortality of hatchery-origin fish after they leave the hatchery. In conjunction with this we are also conducting an experiment to examine size at release as a possible means to improve SAR of hatchery fish.