Estimated loss of juvenile salmonids to predation by northern squawfish, walleyes, and smallmouth bass in John Day Reservoir, Columbia River. [Oncorhynchus spp. ; Ptychocheilus oregonensis; Stizostedion vitreum; Micropterus dolomieu; O. tshawytscha]
- Oregon Dept. of Fish and Wildlife, Clackamas (United States)
- Fish and Wildlife Service, Cook, WA (United States)
The authors estimated the loss of juvenile salmonids Oncorhynchus spp. to predation by northern squawfish Ptychocheilus oregonensis, walleyes Stizostedion vitreum, and smallmouth bass Micropterus dolomieu in John Day Reservoir during 1983-1986. Their estimates were based on measures of daily prey consumption, predator numbers, and numbers of juvenile salmonids entering the reservoir during the April-August period of migration. They estimated the mean annual loss was 2.7 million juvenile salmonids. Northern squawfish were responsible for 78% of the total loss; walleyes accounted for 13% and smallmouth bass for 9%. Twenty-one percent of the loss occurred in a small area immediately below McNary Dam at the head of John Day Reservoir. The authors estimated that the three predator species consumed 14% of all juvenile salmonids that entered the reservoir. Mortality changed by month and increased late in the migration season. Monthly mortality estimates ranged from 7% in June and 61% in August. Mortality from predation was highest for chinook salmon O. tshawytscha, which migrated in July and August. Despite uncertainties in the estimates, it is clear that predation by resident fish predators can easily account for previously explained mortality of out-migrating juvenile salmonids. Alteration of the Columbia River by dams and a decline in the number of salmonids could have increased the fraction of mortality caused by predation over what is was in the past.
- OSTI ID:
- 5756085
- Journal Information:
- Transactions of the American Fisheries Society; (United States), Vol. 120:4; ISSN 0002-8487
- Country of Publication:
- United States
- Language:
- English
Similar Records
Abundance and distribution of northern squawfish, walleyes, and smallmouth bass in John Day Reservoir, Columbia river. [Ptychocheilus oregonensis; Micropterus dolomieu; Stizostedion vitreum]
Abundance and Distribution of Walleye, Northern Squawfish and Smallmouth Bass in John Day Reservoir and Tailrace, 1984 Annual Report.
Related Subjects
13 HYDRO ENERGY
COLUMBIA RIVER
PREDATOR-PREY INTERACTIONS
DAMS
ENVIRONMENTAL IMPACTS
ANADROMOUS FISHES
ECOLOGY
FEEDING
MORTALITY
POPULATION DYNAMICS
WATER RESERVOIRS
ANIMALS
AQUATIC ORGANISMS
FISHES
RIVERS
STREAMS
SURFACE WATERS
VERTEBRATES
540310* - Environment
Aquatic- Basic Studies- (1990-)
130600 - Hydro Energy- Environmental Aspects