Differential predation by northern squawfish Ptychocheilus oregonensis on live and dead juvenile salmonids in the Bonneville Dam tailrace (Columbia River)

Canadian Journal of Fisheries and Aquatic Sciences
By: , and 

Links

Abstract

Juvenile salmonids (Oncorhynchus spp.) that have been killed or injured during dam passage may be highly vulnerable or preferred prey of predators that aggregate below dams. Salmonid loss due to predation will be overestimated using gut content analysis if some prey were dead or moribund when consumed. To examine this issue, field experiments were conducted in the Bonneville Dam tailrace (Columbia River) to compare rates of capture of live and dead juvenile salmonids by northern squawfish (Ptychocheilus oregonensis). Known numbers of coded-wire-tagged live and dead chinook salmon (O. tshawytscha) were released into the tailrace on six nights. Northern squawfish were collected after each release and their gut contents were examined for tags. When 50% of salmon released were dead, northern squawfish consumed 62% dead salmon. When 10% of salmon released were dead, comparable with dam passage mortality, 22% of the tags found in northern squawfish digestive tracts were from dead salmon. These results indicate that predator feeding behavior and prey condition are important considerations when estimating the impact of predation on a prey population.

Study Area

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Differential predation by northern squawfish Ptychocheilus oregonensis on live and dead juvenile salmonids in the Bonneville Dam tailrace (Columbia River)
Series title Canadian Journal of Fisheries and Aquatic Sciences
DOI 10.1139/f94-119
Volume 51
Issue 5
Year Published 1994
Language English
Publisher NRC Research Press
Contributing office(s) Western Fisheries Research Center
Description 8 p.
First page 1197
Last page 1204
Country United States
State Oregon, Washington
Other Geospatial Bonneville Dam