Dam. In the recent capacity experiments it 

 was not possible to obtain a series of aver- 

 age weights of species passed. To have done 

 so would have entailed considerable handling 

 of the fish, a situation we particularly 

 sought to avoid. 



Therefore, in the absence of actual 

 field measurements applicable to these tests, 

 estimated weights were assigned to each spe- 

 cies with respect to season, based in part 

 on the information contained in the fore- 

 going reports. For the tests conducted on 

 July 13 and September 7, the average weight 

 per fish (all species) was estimated at 3 

 and 13 pounds respectively. 



In addition to salmonoids considerable 

 numbers of miscellaneous species pass Bonne- 

 ville Dam each year. The term "scrap" fish 

 has come to be applied locally to the non- 

 salmonoid fishes which have limited or no 

 commercial value. They are generally in 

 peak abundance during early summer, as a 

 rule, shortly after the high water run off. 

 Among those most frequently observed in the 

 fishways at Bonneville Dam are the Columbia 

 River sucker ( Catostomus microcheilus ) , 

 common carp ( Cyprinus carpio ) , squawfish 

 ( Ptyocheilus oregonenis ) and chiselmouth 

 chub ( Achrocheilus alutaceus ). Also present, 

 in addition to the so-called scrap fish, are 

 the shad ( Alosa sapidissima ) , Oregon white- 

 fish ( Prosopium oregonium ) , white sturgeon 

 ( Ancipenser transmontanus ) , asid a fish-like 

 vertebrate, the lamprey ( Entosphenus triden - 

 tatus ) . 



Scrap fish were estimated to range in 

 weight from several ounces (small suckers 

 and squawfish) to over 10 pounds (carp). 

 The majority, however, probably averaged 

 less than 1 pound. As a group they may 

 occasionally be as abundant or more so than 

 the salmonoids. In this regard their pre- 

 sence must not be overlooked since they are 

 in competition with the salmonoids for space 

 in the fishway. 



Species Identification 



As a wide variety of fish could have 

 been present for a given test, it was impor- 

 tant to develop a simple and yet effective 

 method by which to identify the various 

 species. Since all fish generally were 

 visible only momentarily as they passed a 

 weir crest, identification was necessarily 

 confined to a rapid sight recognition of a 



salient feature. Use of the conventional 

 fish identification key was, therefore, of 

 little value under these circumstances, 

 while body conformation and color were occa- 

 sionally useful, we eventually found that 

 dorsal markings provided the most reliable 

 means for rapid field identification of the 

 Salmonoids. For instance, markings on the 

 Chinook salmon were generally large (5 to 

 10 mm.), oblong, blotch-like and numerous. 

 Steelhead dorsal marks were much smaller 

 (2 to 3 mm.), ovoid or nearly so, and numer- 

 ous to very few. On the blueback salmon, 

 dorsal markings were generally absent or 

 extremely rare. The silver salmon more 

 closely resembles the steelhead than any of 

 the other species. Its markings, however, 

 were more rectangular than ovoid, about 3 

 to 4 mm. long and generally quite numerous. 

 The above descriptions apply to the Columbia 

 River salmonoids as we observed them at 

 Bonneville Dam and are not necessary appli- 

 cable to other watersheds frequented by the 

 Pacific salmon and steelhead. Fish other 

 than salmonoids were summarily listed as 

 scrap fish. 



During several initial capacity trials, 

 attempts were made to identify the species 

 composition at each weir. This was soon 

 found to be impracticable as water turbu- 

 lence in the downstream sections of the 

 fishway either prevented or limited the pos- 

 sibility of accurate identification. The 

 crest of the last weir in the fishway was 

 eventually chosen as the site at which to 

 identify the various species. Here rela- 

 tively smooth water flows allowed a more 

 accurate identification. Two observers were 

 always stationed at the final weir, one to 

 record total count and the other to tally 

 species. Total count by minutes was trans- 

 mitted to the operations recorder while 

 species counts were kept manually on a 

 multiple hand-tally array. 



Test Duration 



Following the release of fish from the 

 collection pool, observations at the fishway 

 weirs were generally continued for a period 

 of 60 minutes. The length of the testing 

 period was again arbitrary and as the exper- 

 iments progressed, we occasionally deviated 

 from the assigned one hour test period. 

 However, in general, the 60-minute observa- 

 tion period was established as a standard 

 for comparative purposes. 



10 



