Tucannon River Spring Chinook Salmon Hatchery Evaluation Program 2021 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 Tucannon River spring Chinook caused by hydroelectric projects on the Snake River. 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 2021 to April 2022.

A total of 140 salmon were captured in the TFH trap in 2021 (75 natural adults, 8 natural jacks, 35 hatchery adults, and 22 hatchery jacks). Of these, 115 fish (83 natural, 32 hatchery) were collected for broodstock and 25 adipose clipped strays were killed outright. During 2021, three (2.6%) salmon collected for broodstock died prior to spawning.

Spawning of supplementation fish occurred once a week between 31 August and 28 September, with peak eggtake occurring on 14 September. A total of 166,237 eggs were collected from 38 natural and 9 hatchery-origin female Chinook. Egg mortality to eye-up was 11.9% (19,883 eggs) which left 146,354 live eggs. An additional 0.4% (647) loss of sac-fry left 145,707 BY 2021 fish for production.

Weekly spawning ground surveys began 26 August and were completed by 1 October 2021. A total of 35 redds and 15 carcasses (5 natural, 10 hatchery) were found. Four redds (11% of the total) were counted above the adult trap, even though fish were not intentionally passed upstream. All hatchery origin fish recovered during spawning ground surveys were strays and strays accounted for 41.4% of the run after expansions. Based on redd counts, carcasses recovered, and broodstock collection, the estimated return to the river for 2021 was 215 spring Chinook (101 natural adults, 7 natural jacks and 85 hatchery-origin adults, 22 hatchery jacks).

A total of 42,046 BY20 smolts were direct stream released at TFH on 11 April and 19,974 BY20 smolts were released at the mouth of the Tucannon River on 22 April for a total of 62,020 BY20 smolts released.

Evaluation staff operated a downstream migrant trap to provide juvenile outmigration estimates. During the 2020/2021 emigration, we estimated that 174 natural spring Chinook (BY 2019) smolts emigrated from 1 October 2020 to 6 July 2021 from the Tucannon River.

Smolt-to-adult return rates (SAR) for natural origin salmon are eight times higher on average (based on geometric means) than hatchery origin salmon. However, hatchery salmon survive three times greater than natural salmon from parent to adult progeny over the length of the project. Managers are currently discussing alternative hatchery rearing and release strategies (e.g., hatchery releases below Bonneville Dam, barge transportation, captive broodstock, etc.) in an attempt to increase hatchery fish survival and preserve this stock.