PASSAGE OF SHAD AT THE BONNEVILLE FISHWAYS 



In the last 50 years the catch of shad ( Alosa sapidissima) on the 

 Atlantic coast has dwindled to less than a fifth of its former size. 

 Because of concern about the shad fishery, the Atlantic States Marine 

 Fisheries Commission sponsored legislation that provided for a 6-year 

 study of this valuable natural resource. The Fish and VJildlife Service, 

 as the primary research agency of the Commission, began this study in 

 1950. 



An evident factor in the decline of the shad was the erection of 

 dams that prevented the fish from ascending streams to reach their natural 

 spawning grounds. Although many of these dams had fish ladders intended 

 to pass fish upstream, the shad generally did not use the ladders. Con- 

 sequently, a part of the investigation of the Atlantic-coast shad has been 

 a search for suitable methods of passing shad over obstructions. At the 

 beginning of the study the only fishvjays we knew of that were utilized by 

 shad were those at Bonneville Dam on the Columbia River in the Pacific 

 Northwest, and a soecial study was raade of the passage of shad by those 

 fishways. This paper is a report of that study. 



In the study, William H. Rees (now with the State of Washington 

 Department of Fisheries) made the observations at Bonneville Da-n and com- 

 piled and analyzed part of the data^* C. J. Burner and K. G, Weber made 

 many helpful suggestions during the progress of the studyj R. A. Fredin 

 and Co H. Walburg helped prepare the statistical analysesj C. E. Atkinson 

 helped plan and carry out the study; and Harlan B. Holmes gave special 

 help in obtaining unpublished records, supplied much of the factual 

 information, and suggested methods of analyzing the data. I am indebted 

 to Ivan Donaldson, resident biologist at Bonneville Dam, for his help and 

 suggestions, and to the Corps of Engineers for the use of unpublished 

 records and for the map and ohotographs. 



Description of Bonneville Fish Ladders 



Bonneville Dam is on the Columbia River lUo miles from the ocean. 

 At this site (figo 1) the river is divided into two channels by Bradford 

 Island. The spillway dam is in the north channel, and the powerhouse, 

 which also functions as a dam, is in the south channel. The normal pool 

 level above the dam is at elevation 72 (feet above mean sea level), but 

 during the flood season in spring and summer (the time of shad migration) 

 the level may reach elevation 82.5. During the first 5 years of operation, 

 the pool w^as never raised above the normal 72-foot level. Tailwater below 

 the dam fluctuates from around elevation 8 to as high as elevation 53 

 during flood stages. The level at the time of peak shad migration, usually 

 varies between elevations l5 and 30. The total head on the dam, that is, 

 the height to vjhich shad must climb in the fishways, ranges from kD to 60 

 feet, but most commonly is about 50 feet. 



