An Evaluation of the Influence of Stock Origin and Out-migration History on the Disease Susceptibility and Survival of Juvenile Chinook Salmon

Abstract

Various methods have been developed to mitigate the adverse effects of the Federal Columbia River Power System on juvenile Pacific salmon out-migrating through the Columbia River basin. In this study, we found that hatchery-reared spring Chinook salmon Oncorhynchus tshawytscha in the river are in varying degrees of health, which may affect delayed mortality and the assessment of the effectiveness of management actions to recover listed stocks (e.g., barging fish downstream versus leaving fish in the river). A laboratory disease challenge with Listonella anguillarum was completed on fish from Rapid River Hatchery and Dworshak National Fish Hatchery (NFH) with different out-migration histories: (1) transported by barge, (2) removed from the river before barging, or (3) left to travel in-river. Barged fish from Rapid River Hatchery experienced less mortality than fish from Dworshak NFH. No statistical differences were found between the hatcheries with fish that had in-river out-migration histories. We suggest that the stressors and low survival associated with out-migration through the hydropower system eliminated any differences that could have been present. However, 18–25% of the fish that were barged or collected before barging died in the laboratory before the disease challenge, compared with less than 2% of those that traveled in-river. Owing to disproportionate prechallenge mortality, the disease-challenged populations may have been biased; thus, they were also considered together with the prechallenge mortalities. The synthesis of prechallenge and disease-challenged mortalities and health characteristics evaluated during out-migration indicated that the benefit of barging was not consistent between the hatcheries. This finding agrees with adult survival and delayed mortality estimates for the individual hatcheries determined from adult returns. The results suggest that the health status of fish and their history before entering the hydropower system (hatchery of origin and out-migration path) are critical variables affecting the conclusions drawn from studies that evaluate mitigation strategies.

Received November 18, 2009; accepted January 6, 2011

ACKNOWLEDGMENTS

Funding for this study was provided, in part, by the Anadromous Fish Evaluation Program of the U.S. Army Corps of Engineers (USACE) and NOAA Fisheries Service. Hatchery fish were tagged by Biomark (Scott McCutcheon, Boise, Idaho) and provided by Idaho Fish and Game (IDFG; Sharon Keifer and Ralph Steiner) and U.S. Fish and Wildlife Service (USFWS; Ralph Roseburg). Programming of the PIT tag separation-by-code functions was provided by Dave Marvin, Pacific States Marine Fisheries Commission. The transport tank and assistance were provided by Scott Davidson (NOAA). Assistance in collection and facilities were provided, in part, by Kent Blevins (USACE), Mike Halter (USACE), Doug Marsh (NOAA), Fred Mensik (Smolt Monitoring Program), and Neil Paasch (NOAA) at Lower Granite Dam; Dean Ballinger (Pacific States Marine Fisheries Commission), Jonathan Rerecich (USACE), Timothy Darland (USACE), and Lyle Gilbreath (NOAA) at Bonneville Dam; and Miro Zyndol (USACE) and Terry Hurd (USACE) at the Dalles Dam. Assistance in pathology review was provided by Doug Munson (IDFG), Leslie Lindsay, John Kaufman, and Tony Amandi (Fish Health Section, ODFW), and Kathy Clemens (USFWS). We appreciate the lipid analyses conducted by Daryle Boyd, Karen Tilbury, and Gladys Yanagida from the Northwest Fisheries Science Center. Special thanks are extended to the tugboat captains and crew for their assistance in transferring fish on and off the vessels, as well as Samantha Bund, Nancy Raskauskas, and Amber Roegner at NOAA Fisheries Service and University of California Davis for their assistance in fish transport and care. Finally, we appreciate the many insightful comments provided by Lyndal Johnson, John Ferguson, and Gene Matthews (NOAA).