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Migratory Patterns of Wild Chinook Salmon Oncorhynchus tshawytscha Returning to a Large, Free-Flowing River Basin

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Title Migratory Patterns of Wild Chinook Salmon Oncorhynchus tshawytscha Returning to a Large, Free-Flowing River Basin
Names Eiler, John H. (creator)
Evans, Allison N. (creator)
Schreck, Carl B. (creator)
Date Issued 2015-04-28 (iso8601)
Note To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article was published by the Public Library of Science and is in the public domain. The published article can be found at: http://www.plosone.org/.
Abstract Upriver movements were determined for Chinook salmon Oncorhynchus tshawytscha returning
to the Yukon River, a large, virtually pristine river basin. These returns have declined
dramatically since the late 1990s, and information is needed to better manage the run and
facilitate conservation efforts. A total of 2,860 fish were radio tagged during 2002–2004.
Most (97.5%) of the fish tracked upriver to spawning areas displayed continual upriver
movements and strong fidelity to the terminal tributaries entered. Movement rates were substantially
slower for fish spawning in lower river tributaries (28–40 km d⁻¹) compared to
upper basin stocks (52–62 km d⁻¹). Three distinct migratory patterns were observed, including
a gradual decline, pronounced decline, and substantial increase in movement rate as
the fish moved upriver. Stocks destined for the same region exhibited similar migratory patterns.
Individual fish within a stock showed substantial variation, but tended to reflect the regional
pattern. Differences between consistently faster and slower fish explained 74% of
the within-stock variation, whereas relative shifts in sequential movement rates between
“hares” (faster fish becoming slower) and “tortoises” (slow but steady fish) explained 22% of
the variation. Pulses of fish moving upriver were not cohesive. Fish tagged over a 4-day period
took 16 days to pass a site 872 km upriver. Movement rates were substantially faster
and the percentage of atypical movements considerably less than reported in more southerly
drainages, but may reflect the pristine conditions within the Yukon River, wild origins of
the fish, and discrete run timing of the returns. Movement data can provide numerous insights
into the status and management of salmon returns, particularly in large river drainages
with widely scattered fisheries where management actions in the lower river
potentially impact harvests and escapement farther upstream. However, the substantial
variation exhibited among individual fish within a stock can complicate these efforts.
Genre Article
Access Condition http://creativecommons.org/publicdomain/zero/1.0/
Identifier Eiler, J. H., Evans, A. N., & Schreck, C. B. (2015). Migratory Patterns of Wild Chinook Salmon Oncorhynchus tshawytscha Returning to a Large, Free-Flowing River Basin. PLoS ONE, 10(4), e0123127. doi:10.1371/journal.pone.0123127

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