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Marine Ecology Progress Series

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MEPS 457:251-264 (2012)  -  DOI:

Effects of solar ultraviolet radiation exposure on early ocean survival and fry-to-smolt growth of juvenile salmon

Michael C. Melnychuk1,4,*, Carl J. Walters1, Villy Christensen1, Max L. Bothwell2, David W. Welch3

1Department of Zoology and Fisheries Centre, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
2National Water Research Institute, Environment Canada, Pacific Biological Station, Nanaimo, British Columbia V9T 6N7, Canada
3Kintama Research Services, Nanaimo, British Columbia V9S 3B3, Canada
4Present address: School of Aquatic & Fishery Sciences, University of Washington, Seattle, Washington 98195-5020, USA

ABSTRACT: Marine survival rates of many juvenile salmon populations have declined in recent decades. Although several potential causes have been proposed, there has been little conclusive evidence for which factors are responsible or not responsible for these declines. We experimentally addressed the hypothesis that exposure of coho salmon Oncorhynchus kisutch or sockeye salmon O. nerka to solar ultraviolet-B radiation (UVB) during freshwater rearing of fry and parr life-history stages increases mortality at the time of smoltification and ocean entry. Juvenile coho and sockeye salmon were reared in outdoor hatchery tanks either exposed to full spectrum sunlight or shielded from UVB radiation by plastic screens for up to 9 mo prior to release. Smolts were tagged with acoustic transmitters and detected with hydrophone receivers during their downriver and early ocean migration. Survival of treatment groups was compared using Cormack-Jolly-Seber and Burnham mark-recapture models. While exposure to UVB resulted in decreased growth of juvenile coho salmon, survivorship during the early marine period was unaffected by the UVB treatment for both populations. This first attempt to experimentally address the hypothesis of impaired survival resulting from solar UVB radiation has shown that other factors are more likely responsible for observed declines in salmon marine survival rates.

KEY WORDS: Mortality · Salmonid · Sunlight exposure · Metabolic impairment · Migratory fish · Capture-recapture · Biotelemetry · Mobile tracking

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Cite this article as: Melnychuk MC, Walters CJ, Christensen V, Bothwell ML, Welch DW (2012) Effects of solar ultraviolet radiation exposure on early ocean survival and fry-to-smolt growth of juvenile salmon. Mar Ecol Prog Ser 457:251-264.

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