Table 1. — Number of sockeye salmon tagged at Rock Island 

 Dam and obseried at Zoset Dam in 1933, 1!)S^, 1.962 and 1963 



run. In 1954 and 19G3, tagging was continued for 

 periods of 2 to 4 consecutive days, separated by 

 intervening 3 to 4 day periods of no tagging. Tag- 

 ging was all at the end of the run in 1953 and was 

 confined to the middle portion of the small run in 1 9()L'. 



The method of tagging was standard for these 

 studies. Fish were trapped at Rock Island Dam in 

 either the fish way or forebay (figs. 2 and 3), trans- 

 ported by tank truck to the release sites, tagged, 

 and released. Tagging time seldom exceeded 30 

 seconds per fish. 



Several types and colors of tags were used. 



Petersen plastic disks were used alone in 19G2 and 

 1963, but were used in combination with plastic bars 

 and vinyl streamers in 1953 and 1954. Nickel pins, 

 inserted through the body just below the dorsal fin, 

 provided the attachment. Tags were always ap- 

 plied in pairs, so that the same color and type of 

 tag showed on both sides of the fish. 



STATIONS FOR COUNTING SOCKEYE SALMON 

 AND OBSERVING TAGS 



Zosel Dam, which lies on the Okanogan River at 

 Oroville, Wash., 1 mile below Lake Osoyoos, is the 

 principal upstream location for the observation of 

 tagged lish. The dam, which forms a sawmill pond, 

 is provided with two fishways, each with a trap at its 

 exit for the capture of upstream-migrating fish. 

 Sockeye salmon were counted at Zosel Dam in 

 1935-37, 1944, 1952-57, 1962, and 1963. Since the 

 dam was modified in 1948, however, fish have been 

 able to i)ass upstream at certain water levels without 

 using the fishways. When stream flow exceeds the 



l''i(;uiiK 2. — Fislnv:iy trap, Uock Island Dam. 



134 



U.S. FISH .\ND WILDLIFE .SKUVICK 



