Tucannon River Spring Chinook Salmon Hatchery Evaluation Program: 2010 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. With co-manager agreement, the conventional supplementation production goal was increased in 2006 from 132,000 to 225,000 fish for release as yearlings at a size of 30 g/fish (15 fish per pound). 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 May 2010 to April 2011.

A total of 1,570 salmon were captured in the TFH trap in 2010 (752 natural adults, 22 natural jacks, 731 hatchery adults, and 65 hatchery jacks). Of these, 173 (86 natural, 87 hatchery) were collected and hauled to LFH for broodstock and the remaining fish were passed upstream. During 2010, none of the salmon that were collected for broodstock died prior to spawning.

Spawning of supplementation fish occurred between 1 September and 14 September, with peak eggtake occurring on 1 September. A total of 279,969 eggs were collected from 39 natural and 44 hatchery-origin female Chinook. Egg mortality to eye-up was 11.6% (32,517 eggs), with an additional loss of 9,591 (3.9%) sac-fry. Total fry ponded for 2010 BY production in the rearing ponds was 237,861.

WDFW staff conducted spawning ground surveys in the Tucannon River between 30 August and 1 October, 2010. Two hundred ninety-seven redds and 244 carcasses were found above the adult trap and 184 redds and 140 carcasses were found below the trap. Based on redd counts, broodstock collection, and in-river pre-spawning mortalities, the estimated return to the river for 2010 was 2,525 spring Chinook (1,403 natural adults, 41 natural jacks and 1,003 hatchery-origin adults, 78 hatchery jacks).

Evaluation staff operated a downstream migrant trap to provide juvenile outmigration estimates. During the 2009/2010 emigration, we estimated that 14,778 (12,767-17,978 95% C.I.) natural spring Chinook (BY 2008) smolts emigrated from the Tucannon River.

Smolt-to-adult return rates (SAR) for natural origin salmon were over five times higher on average than hatchery origin salmon. However, hatchery salmon survive almost three times greater than natural salmon from parent to adult progeny. We came close (1,081 fish) to meeting the mitigation goal of 1,152 hatchery origin salmon during 2010. We are currently conducting an experiment to examine size at release as a possible means to improve SARs of hatchery origin spring Chinook.