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Do Dams Make A Difference? Similar Survival Rates For Pacific Salmon In Fraser And Columbia Rivers

Date:
October 30, 2008
Source:
University of British Columbia
Summary:
Canadian and US researchers have made a surprising discovery that some endangered Pacific salmon stocks are surviving in rivers with hydroelectric dams as well as or better than in rivers without dams.

New tagging and tracking technologies showed the surprising result that the survival of juvenile salmon in two major west coast rivers was similar, despite the presence of an extensive network of dams in one river system.
Credit: Welch DW, Rechisky EL, Melnychuk MC, Porter AD, Walters CJ, et al., doi:10.1371/journal.pbio.0060265

Canadian and U.S. researchers have made a surprising discovery that some endangered Pacific salmon stocks are surviving in rivers with hydroelectric dams as well as or better than in rivers without dams.

This is the first study of its kind and is carried out by an international team of scientists that includes researchers from the University of British Columbia.

The team compared the survival rates of out-migrating, juvenile spring Chinook and steelhead salmon from two river basins: the heavily dammed Snake and Columbia Rivers and the free-flowing Thompson and Fraser Rivers – both critical spawning grounds for numerous salmon species.

Using technology that has only recently been available, the team electronically tagged juvenile salmon (smolts) and monitored their journey from freshwater into the ocean via a large-scale acoustic telemetry system called the Pacific Ocean Shelf Tracking (POST) array.

"It came as quite a surprise to us that the Fraser River salmon populations studied have lower survival than the Columbia River study populations," says Erin Rechisky, one of the study authors and a PhD Candidate in the UBC Dept. of Zoology.

Rechisky stresses that there is not yet sufficient evidence to reach any conclusions. "Clearly dams are not good for salmon. What is unclear is whether the Fraser River has a problem that cuts salmon survival to that of a heavily dammed river, or whether factors other than dams play a larger, unsuspected role in salmon survival."

Only in recent years have acoustic tags become small enough for scientists to implant them into juvenile salmon and track them as they migrate downstream. These innovations enabled the team to gather data on salmon smolts in the Fraser River. Before that, it was only possible to measure juvenile survival where salmon gathered in dam bypasses like those in the Columbia and Snake Rivers.

The lower Columbia and lower Snake Rivers currently have eight major hydroelectric dams combined. During the late 1930s when the first dams began to go up, salmon survival rates began to plummet, hitting mortality highs during the 1960s and 1970s due to a combination of warmer waters, fish-grinding turbines and new predators. Since then, the U.S. government has invested in major restoration measures to improve salmon survival rates.

Current conservation efforts have focused on helping smolts pass through the hydropower system. However, the scientific team aims to clarify with future studies using POST technology whether dam passage in itself has long-term detrimental effects that impact salmon's ocean survival.

The researchers note that threats beyond the rivers are taking a heavy toll on salmon. These include habitat destruction, competition with hatchery fish, harvesting and large-scale changes in ocean climate.

The study's lead author is David Welch, Kintama Research Corp., based in Nanaimo, B.C. Along with Rechisky, co-authors are: Michael Melnychuk, UBC Zoology PhD student; Prof. Carl Walters, UBC Fisheries Centre; Prof. Scott McKinley, UBC Land and Food Systems and Canada Research Chair, Aquaculture and the Environment; Aswea Porter, Kintama Research; Oregon State University and the U.S. Geological Survey's Shaun Clements, Benjamin Clemens, and Prof. Carl Schreck.


Story Source:

The above story is based on materials provided by University of British Columbia. Note: Materials may be edited for content and length.


Journal Reference:

  1. Welch DW, Rechisky EL, Melnychuk MC, Porter AD, Walters CJ, et al. Survival of migrating salmon smolts in large rivers with and without dams. PLoS Biol, 6(10):e265 DOI: 10.1371/journal.pbio.0060265

Cite This Page:

University of British Columbia. "Do Dams Make A Difference? Similar Survival Rates For Pacific Salmon In Fraser And Columbia Rivers." ScienceDaily. ScienceDaily, 30 October 2008. <www.sciencedaily.com/releases/2008/10/081028074430.htm>.
University of British Columbia. (2008, October 30). Do Dams Make A Difference? Similar Survival Rates For Pacific Salmon In Fraser And Columbia Rivers. ScienceDaily. Retrieved September 18, 2014 from www.sciencedaily.com/releases/2008/10/081028074430.htm
University of British Columbia. "Do Dams Make A Difference? Similar Survival Rates For Pacific Salmon In Fraser And Columbia Rivers." ScienceDaily. www.sciencedaily.com/releases/2008/10/081028074430.htm (accessed September 18, 2014).

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