In the standard pools id.th fixed weirs in the Bonneville ladders 

 there is a "plunging" type of flow as the water pours over each weir to 

 the pool below. In the plunging type of flow the water is regulated so 

 that it flows over the weir and carries deeply into the ladder pool. This 

 results in a backroll or reverse current on the major portion of the sur- 

 face of the poolo In other words, the direction of flow on most of the 

 surface of the pools is upstream rather than downstream. 



In the plunging type of flow the shad that were seen during the 

 19^0 observations exhibited swimming actions entirely different from those 

 found in most species. In the surface layer they swam into the current, 

 that is, faced downstream, and slowly worked their way backwards toward 

 the head of the pool. When they reached the head of the pool they made a 

 quick turn and swam up over the weir into the next higher pool where the 

 whole operation was repeated,. During the whole operation they exhibited 

 their characteristic behavior of swimming back and forth across the pool, 

 but always faced downstream. 



Later observations by the resident biologist (personal corres- 

 pondence) has shown that many of the shad, in passing from one pool to 

 the next higher pool, rise from the depths of the pool and swim over the 

 weir in a manner similar to other fishes. Those seen on the surface of 

 the pools faced downstream as was previously reported. 



The relative merits of plunging versus streaming flow, so far 

 as shad passage is concerned, cannot be decided at this time. From the 

 experience in passing shad above the counting gate before they were moved 

 to the head of the ladder, it might appear that the streaming type of 

 flow is m.ore suitable for .shad than the plunging type; but since the fish 

 that reach the counting gate have already climbed UO or 5o feet above 

 tailwater through the standard pools where plunging flow prevails, no 

 conclusions are possible. More experimentation on the reactions of shad 

 to various hydraulic conditions is needed to determine the best design 

 and method of operation for this species. 



A watertight chamber equipped ;d.th ;d.ndows for underwater obser- 

 vations was placed in the pool below the Bradford counting station during 

 the shad run of 1950. It was hoped to determine whether shad utilized 

 the submerged openings in the weirs, but the water was too high and turbid 

 to permit observations. 



Other Fishways Ascended by Shad 



Review of the literature has brought to our attention an Atlantic 

 fishway, no longer in operation, that helped many shad over a dam. The 

 report of the Pennsylvania State Commissioners of Fisheries for the years 

 l892-9h (Pennsylvania If 95) has the follomng statement: 



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