Steelhead Trout, Salmo gairdneri 



The 1962 steelhead trout count of 7,591 was 

 almost two and one-half times greater than 

 the 29-year mean of 3,189 (table 1). The count 

 of 15 steelhead on May 1, 1962, was slightly 

 more than one-third the count of 44 on the 

 same day in 1961. 



The greatest monthly number of steelhead 

 passing through the fishways in 1962 occurred 

 in September when 3,429 fish were recorded. 

 Peak monthly movement of these fish in 1961 

 also occurred in September when 3,508 fish 

 were counted. 



Island Dam. Species of fish included are: 

 largescale sucker, Catostomus macrocheilus 

 Girard: longnose sucker, Catostomus catostomus 

 (Forster); squawfish, Ptychocheilus oregonense 

 (Richardson); Rocky Mountain whitefish, 

 Prosopium williamsoni (Girard); Columbia River 

 chub, Mylocheilus caurinus (Richardson); chisel- 

 mouth, Acrocheilus alutaceus Agassiz and 

 Pickering; carp, Cyprinus carpio, Linnaeus; 

 lamprey, Entosphenus tridentatus (Gairdner); 

 shad, Alosa sapidissima (Wilson); Dolly Varden 

 trout, Salvelinus malma (Walbaum); and rain- 

 bow trout, Salmo gairdneri (Richardson). The 

 number of miscellaneous species of fish pass- 

 ing through the fishways was 2.3 times the 

 total salmon and steelhead trout recorded. 



Of the steelhead passing Rock Island Dam 

 in 1962, 70.7 percent utilized the left ladder, 

 while 12.1 and 17.2 percent ascended the 

 middle and right ladders, respectively. 



Additional data pertaining to the movement 

 of steelhead trout at Rock Island Dam are 

 contained in tables 8-14. 



Maximum day's count in 1962 was 284 on 

 September 28 (table 3). In 1961, maximum 

 day's count of 269 occurred on September 19. 



Table 8 shows semimonthly totals of the 

 number and percentage of steelhead trout 

 counted over each fish ladder. 



Miscellaneous Fish 



WEATHER AND RIVER DISCHARGE 

 DATA 



Headwater and tailwater elevations are 

 plotted on figures 1 and 2, respectively. Air 

 temperatures were taken twice daily by pocket 

 thermometer. Water temperatures were taken 

 at the middle fish ladder by recording thermo- 

 graph. Daily records of weather conditions 

 and stream flows are shown on tables 9-14. 

 Daily river discharge data are plotted on 

 figure 3. Maximum daily discharge of 326,900 

 c.f.s. on June 5, 1962, was slightly less than 

 two-thirds the flow of 488,500 c.f.s. on the 

 same day in 1961. Maximum daily discharge 

 of 526,900 c.f.s. in 1961 occurred on June 12. 

 Maximum water temperature in 1962 of 65 

 degrees occurred on July 28 and 29. Maximum 

 water temperature in 1961 of 67 degrees 

 occurred on August 21. 



In 1962, enumeration was made of species 

 of fish other than salmon and steelhead trout 

 passing Rock Island Dam (tables 15-20). No 

 claims are made as to complete accuracy of 

 identification of these fish. It is felt, however, 

 that the degree of accuracy is consistent with 

 that maintained at other dams on the Columbia 

 River and as such may be used as a rough 

 index of abundance of these fish. In 1962, 

 approximately 165,000 fish other than 

 salmon and steelhead trout passed Rock 



ACTIVITIES AND OBSERVATIONS 



As in past years of counting at Rock Island 

 Dam, some fish were observed with cuts or 

 abrasions on the body. Of 71,735 salmon and 

 steelhead observed as they passed over the 

 counting boards, 364, or approximately 0.5 

 percent, had injuries of some sort either on 

 the body or about the head. Of 40,764 salmon 

 and steelhead observed in 1961, 1.0 percent 

 had injuries about the head or body. Since in 



