Behavior and movement of formerly landlocked juvenile coho salmon after release into the free-flowing Cowlitz River, Washington

Northwestern Naturalist
By: , and 

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Abstract

Formerly landlocked Coho Salmon (Oncorhynchus kisutch) juveniles (age 2) were monitored following release into the free-flowing Cowlitz River to determine if they remained in the river or resumed seaward migration. Juvenile Coho Salmon were tagged with a radio transmitter (30 fish) or Floy tag (1050 fish) and their behavior was monitored in the lower Cowlitz River. We found that 97% of the radio-tagged fish remained in the Cowlitz River beyond the juvenile outmigration period, and the number of fish dispersing downstream decreased with increasing distance from the release site. None of the tagged fish returned as spawning adults in the 2 y following release. We suspect that fish in our study failed to migrate because they exceeded a threshold in size, age, or physiological status. Tagged fish in our study primarily remained in the Cowlitz River, thus it is possible that these fish presented challenges to juvenile salmon migrating through the system either directly by predation or indirectly by competition for food or habitat. Given these findings, returning formerly landlocked Coho Salmon juveniles to the free-flowing river apparently provided no benefit to the anadromous population. These findings have management implications in locations where landlocked salmon have the potential to interact with anadromous species of concern.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Behavior and movement of formerly landlocked juvenile coho salmon after release into the free-flowing Cowlitz River, Washington
Series title Northwestern Naturalist
DOI 10.1898/11-07.1
Volume 92
Issue 3
Year Published 2011
Language English
Publisher Society for Northwestern Vertebrate Biology
Publisher location Bethesda, MD
Contributing office(s) Western Fisheries Research Center
Description 8 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Northwestern Naturalist
First page 167
Last page 174
Country United States
State Washington
Other Geospatial Cowlitz River