Tucannon River Spring Chinook Salmon Hatchery Evaluation Program: 2011 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 5,760 (1,152 above the project area and 4,608 below the project area for harvest) Tucannon River spring Chinook 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 2011 to April 2012.

A total of 783 salmon were captured in the TFH trap in 2011 (340 natural adults, 60 natural jacks, 157 hatchery adults, and 226 hatchery jacks). Of these, 166 (89 natural, 77 hatchery) were collected and hauled to LFH for broodstock and the remaining fish were passed upstream. During 2011, none of the salmon that were collected for broodstock died prior to spawning.

Spawning of supplementation fish occurred between 30 August and 20 September, with peak eggtake occurring on 6 September. A total of 325,701 eggs were collected from 45 natural and 41 hatchery-origin female Chinook. Egg mortality to eye-up was 4.5% (14,551 eggs), with an additional loss of 5,935 (1.9%) sac-fry. Total fry ponded for 2011 BY production in the rearing ponds was 305,215.

WDFW staff conducted spawning ground surveys in the Tucannon River between 29 August and 30 September, 2011. One hundred sixty-five redds and 109 carcasses were found above the adult trap and 132 redds and 83 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 2011 was 1,300 spring Chinook (671 natural adults, 85 natural jacks and 263 hatchery-origin adults, 281 hatchery jacks).

Evaluation staff operated a downstream migrant trap to provide juvenile outmigration estimates. During the 2010/2011 emigration, we estimated that 45,538 (41,083-51,349 95% C.I.) natural spring Chinook (BY 2009) 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. Based on density-dependent effects we have observed, the mitigation goal may be higher than the habitat can support under current habitat conditions.