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Ocean Tracking Project Garners Data on
Salmon Survival Downstream of Hydrosystem

by Staff
Columbia Basin Bulletin, July 10, 2009

A first-ever sampling of juvenile salmon survival during the initial leg of their ocean journey would indicate they do not suffer negative after-effects from their journey down through the Columbia-Snake river hydro projects, according to a research paper published in the peer-reviewed Canadian Journal of Fisheries and Aquatic Sciences.

"It is not correct to conclude that the dams currently play no role in affecting survival, simply that any contributory effect appears to be small," the paper concludes.

Data collected in 2006 as part of the long-term study showed that yearling hatchery spring chinook that traveled through eight dams survived as well to southeast Washington's Willapa Bay as did young fish that only had to hurdle four dams.

The paper, "Experimental measurement of hydrosystem-induced delayed mortality in juvenile Snake River spring Chinook salmon (Oncorhynchus tshawytscha) using a large-scale acoustic array," was produced by Erin L. Rechisky, David W. Welch, Aswea D. Porter, Melinda C. Jacobs and Adrian Ladouceur.

The research paper can be found here.

Lead author Erin Rechisky is doctoral candidate at the Fisheries Centre, University of British Columbia. Welch is president of Kintama Research, the chief architect of the design for the current "POST" array and principal investigator on the research program reported in the paper. Porter, Jacobs, and Ladouceur were all Kintama Research employees at the time of the study.

POST, the Pacific Ocean Shelf Tracking project, is a tool for tracking the movements of marine animals along the west coast of North America using acoustic transmitters implanted in a variety of species and a series of receivers in lines across the continental shelf.

The telemetry receiver arrays implemented and operated by Kintama that were used in this study are part of Kintama's contribution to the POST array and through POST to the Census of Marine Life. Kintama's contribution to the west coast POST array currently spans more then 2,500 kilometers of the Pacific Northwest, from the Snake River to southeast Alaska.

The paper says that "survival from out-migration until adult return is substantially lower for wild and hatchery Snake River spring chinook salmon relative to some mainstem Columbia River populations" so it has been hypothesized that the cause is cumulative stress from dam passage. To test the theory, the authors say, survival data must be measured downstream of the hydrosystem and in the ocean. Until recently, the technology was not available to collect that data.

As exciting as the results themselves is the fact that, with new technology, "we can actually measure survival in the ocean," Rechisky said.

"Our study is the first to estimate survival in the coastal ocean and demonstrates the utility of a large-scale array in testing previously intractable hypothese," the paper says.

For the study, 800 young spring chinook were outfitted with acoustic and PIT tags. Half of the fish were produced at Dworshak National Fish Hatchery in the Clearwater River drainage in central Idaho and half were produced at the Cle Elum supplementation and Research Facility on the Yakima River, a tributary to the Columbia River. The Clearwater feeds into the Snake River and then the Columbia.

The Snake River fish pass through four lower Snake River dams and four lower Columbia River dams on the way to the Pacific Ocean. The Yakima salmon only have to negotiate the lower Columbia River dams.

Willapa Bay is located on the south Washington coast north of the Columbia's mouth. The first ocean detection line there is about five days swim (for the juvenile salmon), or 274 kilometers from the lowest dam in the Columbia system, Bonneville.

"There was no detectable difference in survivorship from release to Willapa Bay between populations, and the mean time for smolts to reach this line after passing Bonneville dam was five days for both," the paper says. "Therefore, delayed mortality was not evident after several days in the coastal ocean at a point located 274 km beyond the hydrosystem." The researchers estimated that 29 percent of the tagged Snake River fish and 28 percent of the Yakima fish survived to Willapa Bay.

The 2006 data indicates that 40 percent of the Snake River releases and 36 percent of the Yakima fish survived from their release to a point just below Bonneville Dam.

"Our results imply that if delayed mortality causes the disparity in adult return rates of hatchery-origin Snake River spring chinook salmon, it is at a time and place more distant from the Columbia River; however it is plausible that delayed mortality may operate on smaller fish that were not tested here." The study employed fish that were 140 millimeters long or longer.

Ocean Tracking Project Garners Data on Salmon Survival Downstream of Hydrosystem
Columbia Basin Bulletin, July 10, 2009

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