ECOLOGY: Early Life Experiences

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Science  31 Oct 2008:
Vol. 322, Issue 5902, pp. 651c
DOI: 10.1126/science.322.5902.651c

The decline of Columbia River salmon may be one sign of the human impact on fisheries, and it has been argued that some of the Columbia River dams should be removed in order to reduce the hazards encountered by salmon smolts as they make their way from the spawning grounds to the sea. In order to assess migration losses in the Thompson-Fraser (which is not dammed) and the Snake-Columbia (which is) river systems in North America, Welch et al. measured the survival rate of Chinook and steelhead smolts with implanted acoustic tags. Surprisingly, their data suggest that the survival rates of juvenile fish making these journeys are comparable; in fact, they are somewhat higher in the hydroelectric power-generating portion of the Columbia. Two corollaries to be examined are (i) whether the Fraser River imposes an unidentified toll on juvenile survival, and (ii) whether the transit through the systems of dams exacts a later cost in terms of ocean mortality. — LMZ

PLoS Biol. 6, e265 (2008).

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