ANNUAL FISH PASSAGE REPORT - 



ROCK ISLAND DAM 



COLUMBIA RIVER, WASHINGTON, 1959 



by 



Paul D. Zimmer, Clifton C. Davidson 



and Floyd S. Anders 



Fishery Biologists (Management) 



ABSTRACT 



Important runs of salmon and steelhead pass Rock Island Dam on 

 the Columbia River. Annual records of fish movement past the dam 

 are available from 1933. 



Count of 23,352 chinook salmon in 1959 was less than half the peak 

 year of 1957. Sockeye count of 72,351 exceeded the 26-year mean of 

 52,073. Only 118 coho salmon were recorded. Greatest count of coho, 

 229, occurred in 1947. Numbers of steelhead passing Rock Island 

 Dam increased in 1959. The 26-year mean of 2,900 steelhead was 

 less than 1959 count of 4,138. 



INTRODUCTION 



Rock Island Dam, located on the 

 Columbia River approximately 1 2 miles 

 downstream from the city of Wenatchee, 

 Wash., has been in operation since 1933. 

 The plant is ow^ned and operated by 

 Chelan County Public Utility District. 



This report on passage of fish at 

 Rock Island Dam during 1959 provides 

 information on operation of fishways 

 and numbers of salmon and steelhead 

 utilizing upstream fish passage facil- 



Note.--Paul D. Zimmer and Clifton C. Davidson (de- 

 ceased), Bureau of Commercial Fisheries Columbia River 

 Portland Program Office, U.S. Fish and Wildlife Service, 

 Portland, Oregon; and Floyd S. Anders, Bureau of Com- 

 mercial Fisheries Branch of Resource Management, U.S. 

 Fish and Wildlife Service, Washington, D. C. 



ities. Fish other than salmon and steel- 

 head were not enumerated during the 

 period of "spot counting", hence data 

 pertaining to their numbers are not 

 included m this report. 



Rock Island Dam is now equipped 

 with three fishways: one located on the 

 right bank, another on the left bank, 

 and the third approximately in the 

 center of the dam. Two of the fish 

 ladders were placed in operation in 

 1933, and the third (middle ladder) was 

 constructed in 1935-36. All three lad- 

 ders have undergone significant modi- 

 fications since initial construction. 



Included in this report are comments 

 covering various investigations carried 

 on at Rock Island during 1959. 



