Tucannon River Spring Chinook Salmon Hatchery Evaluation Program: 2009 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 2009 to April 2010.

A total of 1,225 salmon were captured in the TFH trap in 2009 (327 natural adults, 63 natural jacks, 410 hatchery adults, and 425 hatchery jacks). Of these, 177 (89 natural, 88 hatchery) were collected and hauled to LFH for broodstock and the remaining fish were passed upstream. During 2009, two salmon that were collected for broodstock died prior to spawning.

Spawning of supplementation fish occurred between 25 August and 22 September, with a peak eggtake occurring on 8 September. A total of 323,341 eggs were collected from 42 natural and 54 hatchery-origin female Chinook. Egg mortality to eye-up was 7.5% (24,129 eggs), with an additional loss of 6,921 (2.3%) sac-fry. Total fry ponded for 2009 BY production in the rearing ponds was 292,291.

WDFW staff conducted spawning ground surveys in the Tucannon River between 27 August and 1 October, 2009. Two hundred ninety-two redds and 268 carcasses were found above the adult trap and 159 redds and 199 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 2009 was 1,862 spring Chinook (634 natural adults, 116 natural jacks and 605 hatchery-origin adults, 507 hatchery jacks).

Evaluation staff operated a downstream migrant trap to provide juvenile outmigration estimates. During the 2008/2009 emigration, we estimated that 8,529 (7,059-10,592 95% C.I.) natural spring Chinook (BY 2007) smolts emigrated from the Tucannon River. Low estimates may be due to low capture probabilities because of high spring flows during 2009 or low survival. Smolt-to-adult return rates (SAR) for natural origin salmon average about five times higher than for hatchery origin salmon. However, hatchery salmon survive almost three times greater than natural salmon from parent to adult progeny. We came close (1,112 fish) to meeting the mitigation goal of 1,152 hatchery origin salmon during 2009. We are currently conducting an experiment to examine size at release as a possible means to improve SARs of hatchery origin spring Chinook.