System-Wide Significance of Predation on Juvenile Salmonids in Columbia and Snake River Reservoirs : Annual Report 1992.
Northern squawfish (Ptychocheilus oregonensis) predation on juvenile salmonids was characterized during 1992 at ten locations in the Columbia River below Bonneville Dam and at three locations in John Day Reservoir. During the spring and summer, 1,487 northern squawfish were collected in the lower Columbia River and 202 squawfish were sampled in John Day Reservoir. Gut content data, predator weight, and water temperature were used to compute a consumption index (CI) for northern squawfish, and overall diet was also described. In the Columbia River below Bonneville Dam, northern squawfish diet was primarily fish (spring 69%; summer 53%), most of which were salmonids. Salmonids were also the primary diet component in the Bonneville Dam tailrace, John Day Dam forebay, and the McNary Dam tailrace. Crustaceans were the dominant diet item at the John Day mid-reservoir location, although sample sizes were small. About half of the non-salmonid preyfish were sculpins. The consumption index (CI) of northern squawfish was generally higher during summer than during spring. The highest CI`s were observed during summer in the tailrace boat restricted zones of Bonneville Dam (CI = 7.8) and McNary Dam (CI = 4.6). At locations below Bonneville Dam, CI`s were relatively low near Covert`s Landing and Rooster Rock, higher at four locations between Blue Lake and St. Helens, and low again at three downriver sites (Kalama, Ranier, and Jones Beach). Northern squawfish catches and CI`s were noticeably higher throughout the lower Columbia compared to mid-reservoir sites further upriver sampled during 1990--92. Predation may be especially intense in the free-flowing section of the Columbia River below Bonneville Dam. Smallmouth bass (Micropterus dolomieui; N = 198) ate mostly fish -- 25% salmonids, 29% sculpins, and 46% other fish. Highest catches of smallmouth bass were in the John Day Dam forebay.
- Research Organization:
- US Fish and Wildlife Service
- Sponsoring Organization:
- US Bonneville Power Administration
- DOE Contract Number:
- AI79-90BP07096
- OSTI ID:
- 10119290
- Report Number(s):
- DOE/BP-07096-3; ON: DE94006088
- Country of Publication:
- United States
- Language:
- English
Similar Records
System-Wide Significance of Predation on Juvenile Salmonids in Columbia and Snake River Reservoirs : Annual Report of Research 1990.
Feeding Activity, Rate of Consumption, Daily Ration and Prey Selection of Major Predators in John Day Reservoir, 1984 : Annual Report.
System-Wide Significance of Predation on Juvenile Salmonids in the Columbia and Snake River Reservoirs : Annual Report of Research 1991.
Technical Report
·
Thu Feb 28 23:00:00 EST 1991
·
OSTI ID:6058370
Feeding Activity, Rate of Consumption, Daily Ration and Prey Selection of Major Predators in John Day Reservoir, 1984 : Annual Report.
Technical Report
·
Tue Jul 01 00:00:00 EDT 1986
·
OSTI ID:5498471
System-Wide Significance of Predation on Juvenile Salmonids in the Columbia and Snake River Reservoirs : Annual Report of Research 1991.
Technical Report
·
Mon Dec 31 23:00:00 EST 1990
·
OSTI ID:7076789