Spawning Migration of Adult Chinook Salmon (Oncorhynchus tshawytscha) Carrying External and Internal Radio Transmitters

Abstract

Upstream movements of radio-tagged and control adult chinook salmon (Oncorhynchus tshawytscha) were monitored during the spring and fall 1976 and spring 1977 in the lower Snake River, southeastern Washington. Travel time from point of fish release and percent return to upstream tracking facilities were compared for experimental and control fish. Experimental fish carried anchor tags, and either internal or external radio transmitters. Control fish carried anchor tags only. Chinook salmon that lost external transmitters moved upriver more slowly than control fish although percent returns to upriver trapping facilities were similar. Travel times and percent returns of chinook salmon that retained external transmitters did not differ significantly from control fish. Although some salmon tagged with internal transmitters moved upriver, all failed to cross Little Goose Dam 6.5 km from the release site. Most internally tagged salmon eventually travelled downstream.