NOTES 



FEEDING ECOLOGY OF WALLEYE, 



STIZ0STED10N VITREUM VITREUM, IN THE 



MID-COLUMBIA RIVER, WITH EMPHASIS ON 



THE INTERACTIONS BETWEEN WALLEYE 



AND JUVENILE ANADROMOUS FISHES 1 



The walleye, Stizostedion vitreum vitreum, is 

 widely distributed in the United States and 

 Canada and has been studied throughout most of 

 its native range (Colby et al. 1979). The walleye is 

 exotic to the Pacific Northwest and its biology here 

 has not been fully investigated. The exact cir- 

 cumstances of walleye introduction into the Co- 

 lumbia River system are not documented; how- 

 ever, this piscivorous, cool-water fish is found 

 throughout the mid-Columbia River (Fig. 1) and 

 downstream of Bonneville Dam (Durbin 2 ). As 

 populations of walleye in the Columbia River have 

 increased and their range extended, interest in 

 them has focused on the potential sport fishery for 

 walleye and on the impact of walleye on native 

 salmonid populations (Carlander et al. 1978; 

 Brege 1981). 



'Technical Paper No. 6722, Oregon Agricultural Experiment 

 Station. Oregon State University. Corvallis, Oreg. 



2 Durbin, K. 1977. News column. Oregon Department of Fish 

 and Wildlife, Portland, Oreg. 



Pacific 

 Ocean 



FIGURE 1. — Map of the lower and mid-Columbia River showing 

 the locations of the major dams and the John Day pool study area 

 where walleye were collected during 1980 and 1981. 



FISHERY BULLETIN: Vol. 82, No. 2, 1984. 



Construction of dams has transformed the Co- 

 lumbia River into a series of low velocity im- 

 poundments with physical characteristics (Table 

 1) that are well suited for walleye (Colby et al. 

 1979). Thus, the Columbia River fits the model for 

 ideal walleye habitat proposed by Kitchell et al. 

 ( 1977 ). This transformation has increased the time 

 required for emigration of juvenile salmonids and 

 increased their mortality partly due to increased 

 predation (Raymond 1979). 



The purpose of this study was to describe the 

 spring and summer feeding ecology of walleye in 

 the John Day pool of the Columbia River. Em- 

 phasis was placed on walleye interaction with 

 juvenile salmonids and young-of-the-year Ameri- 

 can shad, Alosa sapidissima, an anadromous fish 

 that is morphologically and behaviorally similar 

 to outmigrant salmonids and is abundant in the 

 Columbia River in the late summer. We concen- 

 trated on seasonal variation in walleye diets, diel 

 feeding periodicity, and food selection as influ- 

 enced by walleye size. Preliminary findings re- 

 garding the spring diets of these walleye were 

 reported by Maule (1982). 



TABLE 1. — Summary of limnological data for the John Day pool 

 of the Columbia River, from Hjort et al. ( 1981 1. All data collected 

 in August 1979, except for surface temperatures, which were 

 taken in 1981. 



Characteristic 



Range for 

 John Day pool 



Range for 

 study area 



We collected walleye for this study in the first 23 

 km of the John Day pool immediately downstream 

 from McNary Dam on the Columbia River (Fig. 1) 

 from 2 April to 30 September 1980 and from 30 

 March to 30 September 1981. During each month 

 we attempted to collect a minimum of 10 walleye 

 during each of four generalized times of day : dawn, 

 midday, dusk, and night. In 1980 we captured 



411 



