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11-08-2010, 02:52 PM #1
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The effects of the 1983 El Nino on Oregon's Coho (Oncorhynchus kisutch) and Chinook (
By Steven L. Johnson
Fisheries Research, Volume 6, Issue 2, January 1988, Pages 105-123, ISSN 0165-7836, DOI: 10.1016/0165-7836(88)90031-8.
The 1983 El Nino event off the Pacific Coast of North America resulted in increased adult mortality and decreased average size for Oregon's coho and chinook salmon. Actual return of adult coho salmon to the Oregon Production Area in 1983 was only 42% of the pre-season prediction. Coho smolts entering the ocean in the spring of 1983 also survived poorly, resulting in low adult returns again in 1984. Abundance of chinook stocks in southern Oregon was also reduced, as was abundance of Columbia River chinook stocks that show localized ocean distribution. Northerly migrating chinook stocks from the Columbia River showed little or no decline in abundance. The average weight of coho and chinook salmon landed in 1983 by Oregon's commercial troll fishery was the lowest recorded since statistics were first recorded in 1952. Comparison of the length-weight relationship for these fish indicated coho and chinook were in poorer condition in 1983 than in non-El Nino years. Because adult coho salmon returned to hatcheries at a smaller size, the fecundity (eggs per female) in 1983 was reduced from the 1978-1982 average by 24% at coastal hatcheries and by 27% at Columbia River hatcheries. The fecundity of chinook salmon was unchanged at most hatcheries.