Tucannon River Spring Chinook Salmon Captive Broodstock Program: Final Project Completion Report

This report summarizes the objectives and accomplishments of the Tucannon River Spring Chinook Salmon Captive Broodstock Program. The WDFW initiated a captive program in 1997. The captive program collected sac fry from the hatchery supplementation program from five (1997-2001) brood years (BY) with additional sac fry collected from the 2002 BY in order to have extra captive males on hand to spawn. The overall goal of the Tucannon River captive program was for the short-term rebuilding of the Tucannon River spring Chinook salmon population, with the hope that natural production would sustain the population in the future. The project goal was to rear captive salmon selected from the supplementation program to adults, spawn them, rear their progeny, and release approximately 150,000 smolts annually into the Tucannon River between 2003-2007. This was expected to provide a return of about 300 adult fish to the Tucannon River of captive origin per year between 2005-2010. These smolts, in combination with the current conventional hatchery supplementation program and natural production, were expected to produce 600-700 returning adult spring Chinook to the Tucannon River each year from 2005-2010.

Selecting fry from parents based on Bacterial Kidney Disease (BKD) screening appeared to have benefited the program, as BKD was not an issue with the Tucannon captive broodstock as it has been with other Chinook salmon captive brood programs. Overall survival and health of captive brood adults was good throughout the duration of the program.

Adult spawners from the captive program were significantly smaller than conventional hatchery and natural origin fish. The captive broodstock produced significantly larger eggs, but egg quality was poor, with high egg mortality. The large eggs in small adults resulted in significantly lower fecundity, relative fecundity, and reproductive mass in captive females compared to conventional hatchery and natural origin females of the same age.

During 2002, adult captive broodstock determined to be in excess of broodstock needs were outplanted into the upper Tucannon River in order to stay within the approved release goal of 150,000 smolts. Due to the low frequency of natural spawning by released fish, high mortality due to evidence suggesting predation and illegal harvest, and high egg mortality in the hatchery during 2002, the priority for excess fish in the future was changed. The co-managers agreed to spawn excess adults, and release their progeny as parr.

The captive program did provide additional smolts for release that otherwise would not have occurred had the program not been in place. Downstream survival rates of smolts based on PIT tagging revealed that survival tended to be higher every year for conventional hatchery fish compared to captive progeny. However, with the exception of the 2006 brood year, differences were not significant.

As anticipated, due to their protection in the hatchery environment, egg-to-parr, parr-to-smolt, and egg-to-smolt survivals of captive progeny and conventional hatchery fish were higher than natural origin fish. However, egg-to-parr and egg-to-smolt survivals were higher for conventional hatchery fish than captive progeny. Smolt-to-adult return (SAR) survival has effectively been < 0.02% for the first five years of the captive program compared to SARs of 0.13% and 1.07% for conventional hatchery and natural origin fish, respectively. Captive progeny size at release was increased from 30 g/fish to 50 g/fish for the 2005 and 2006 brood years. We are cautiously optimistic this change will increase SAR survival.

Based on adult returns from the 2000-2005 brood years, captive program produced only 0.17 adults for every spawner which is considerably lower than naturally reared salmon that produced 0.67 adults for every spawner. Conventional hatchery reared fish produced 1.66 adults per spawner and was usually the only group to return adults above replacement levels. It is unknown whether hatchery domestication effects or other unknown factors have played a role in the poor returns, as the captive progeny and conventional hatchery fish are reared and released in the same manner. Based on the results to date, the Tucannon River spring Chinook captive broodstock program has been unsuccessful in achieving its adult return goals.

The WDFW LSRCP evaluation program will continue to document returning adults from the captive program and compare their survival to survivals from the conventional hatchery supplementation program and natural origin fish. A final assessment of the captive program will be submitted for publication in a peer-reviewed journal after the final adults return in 2011.