Effect of Flow on Performance and Behavior of 

 Chinook Salmon in Fishways^ 



by 



CLARK S. THOMPSON, Fishery Biologist 



Bureau of Commercial Fisheries 

 Biological Laboratory 

 Seattle, Wash. 98102 



ABSTRACT 



Adult fall- run chinook salmon ( Oncorhynchus tshawytscha ) were studied during 

 plunging and streaming conditions of flow in a pool-and-overfall fishway that per- 

 mitted recycling of fish after each completed circuit. Flows were controlled by ad- 

 justment of valves in a lock at the head of the fishway. Individual fish were timed as 

 they ascended a specified number of pools under each condition. 



Combined data on the performance of individual fish and comparisons of com- 

 bined data from all fish tested suggest that plunging and streaming flows may be 

 equally suitable for the passage of chinook salmon in a pool-and-overfall fishway. 

 About 60 percent of the fish ascended slightly faster in the streaming flow, but the 

 average rate of ascent for all fish was slightly higher in a plunging flow. 



Orientation of the fish is described in relation to type and velocity of flow. Most 

 fish preferred to rest in the lower downstream quadrant of the pool in a plunging 

 flow; conversely, the lower upstream quadrant was preferred in a streaming flow. 

 Resting fish always faced the current. 



INTRODUCTION 



Pool-and-overfall fishways may operate un- 

 der two types of flow: (1) a plunging flow in 

 which the directional current reaches the bot- 

 tom of each fishway pool or (2) a stream- 

 ing floW/'vwhich a strong directional current 

 passes along the top of the pools (fig. 1). Pres- 

 ent criteria for pool-and-overfall fishways on 

 the Columbia River stipulate that flows be 

 uniform with a 30.5-cm. to a 38.1 -cm. depth 

 over the weirs. ^ Clay (1961) stated that with 

 a head (depth) on the weir up to 35.6 cm., Pa- 

 cific salmon are able to ascend a fishway 

 where stable streaming flow exists but it is 

 better to limit this head to just under 30.5 cm. 

 or the upper limit of stable plunging flow. The 

 U.S. Army Corps of Engineers (1958) made 

 tests at The Dalles Dam to determine if fish 

 preferred a 45.7-cm. or a 30.5-cm. depth 



■'■ Financed by U.S. Army Corps of Engineers as part 

 of a broad program of fishery-engineering research to 

 provide design criteria for fish-passage facilities at 

 Corps projects on the Columbia River. 



2 Bureau of Commercial Fisheries. 1958. Anadro- 

 mous fish passage at dams In the Pacific Northwest. Bur. 

 Commer. Fish., 811 N.E. Oregon, P.O. Box 4332, Port- 

 land, Oreg. 97208, 10 pp. [Processed.] 



over the weirs. More fish passed the counting 

 station at high, or streaming flows, than at 

 low, on plunging flows. 



White and Nemenyi (1942) studied pool over- 

 falls of more than 10 weir profiles in a model 

 flume with constant flows. In a number of ex- 

 amples they showed how submerged flow (plung- 

 ing) is supplanted by surface flow (streaming) 

 through alterations of the fall between pools, 

 thickness of weirs, and design of the weir 

 crest. 



Streaming flow developed when box culverts 

 were weired, but the flows were unsatisfactory 

 because of shallow depths (McKinleyand Webb, 

 1956). Even at relatively low discharges the 

 water tended to go into a streaming motion. 

 The authors added that a successful pool-and- 

 weir fishway requires complete dissipation of 

 kinetic energy of the water in each pool. SvLf- 

 ficient water is also required for the fish to 

 jump the barriers. 



During a test of fishway capacity, EUing 

 and Raymond (1959) noted how nonuniform 

 fishway flows affected the passage of fish. 

 When unstable flows changed from plunging to 

 streaming, fish delayed their passage for 

 about 5 minutes. After the delay, the migrants 

 apparently became conditioned to the changed 

 flows and continued their ascent. 



