Index of Predation on Juvenile Salmonids by Northern Squawfish in the Lower and Middle Columbia River and in the Lower Snake River

Report on the Predation Index, Predator Control Fisheries, and Program Evaluation for the Columbia River Basin Experimental Northern Pikeminnow Management Program, 2008 Annual Report.

“…In addition, walleye scales collected during tagging operations in 2008 were used to supplement those collected during the indexing season. From fish ≥200 mm FL we measured total body weight (g), collected and preserved digestive tracts from northern pikeminnow, and recovered the digestive tract contents from smallmouth bass and walleye using methods described by Ward et al (1995). We noted sex (male, female, or undetermined) and maturity (undetermined, immature, developing, ripe, or spent) while collecting northern pikeminnow digestive tracts.…”

“…Details of laboratory methods are given in Ward et al (1995). Standard methods of determining ages from scales were used (DeVries and Frie 1996).…”

Post-Release Attributes and Survival of Hatchery and Natural Fall Chinook Salmon in the Snake River; 2000-2001 Annual Report.

“…Most predation studies in the Columbia River basin have been focused on reservoirs, as well as passage-related problems at hydroelectric projects Ward et al 1995;Naughton 1998). The need to examine predation in other areas of the basin has been noted, especially in salmonid rearing areas (Gray and Rondorf 1986;Tabor et al 1993).…”

Post-Release Attributes and Survival of Hatchery and Natural Fall Chinook Salmon in the Snake River : Annual Report 1999.

“…in several parts of the Columbia River Basin has been examined Ward et al 1995). Predation studies in the Columbia River in the 1980's implicated the northern pikeminnow Ptychocheilus oregonensis, smallmouth bass Micropterus dolomieu, walleye Stizostedion vitreum, and channel catfish Ictalurus punctatus as aquatic predators of emigrating juvenile salmon Rieman et al 1991).…”