center ladder, 11.6 percent; and right ladder, 

 14.7 percent. 



This report describes tagging details and the 

 results of experiments at Rock Island Dam to 

 determine whether the dam caused loss or delay 

 to these runs, and whether loss or delay was 

 associated with the failure of fish to find and use 

 the dam's right bank fishway. 



Table 1. — Chinook and sockeye salmon and steelhead 

 trout counted at Rock Island Dam, 1933-56 ' 



i Silver salmon (O. kisulch) averaged about 60 fish per year during this 

 period. 



' Grand Coulee Dam blocked upriver migration commencing this year. 



METHOD OF TAGGING 



Preliminary experiments on tagging and meth- 

 ods of catching salmon were performed in 1953 

 followed by full-scale experiments in 1954 through 

 1956 on chinook {Oncorhynchus tshawytscha) and 

 sockeye salmon (O. nerlca). We planned to tag 

 steelhead trout (Salmo gairdneri) but too few 

 (17 to 32 each year) were captured and tagged for 

 subsequent analysis. 



Salmon were trapped at the upstream edge of 

 the counting boards within the left and right 

 fishways and at the upstream outlet of the left 

 ladder. (Earlier attempts to catch quantities of 

 fish for tagging below the dam were unsuccessful.) 

 The trapped fish were transferred to tank trucks 

 and hauled to the tagging sites located approxi- 

 mately 1,000 feet below the dam on each side of 

 the river in 1954 and 1955. In 1956, tagged sal- 

 mon were released off the downstream face of the 

 dam close to the left or right ladder. The fish 



Grond Coulee Dam 



Leavenworth 

 Hatchery 



Rock Island 

 Dam 



Figure 1. — Columbia River watershead between Rock 

 Island and Grand Coulee Dams. 



were lowered to water level in canvas bags filled 

 with water (fig. 4). Forebay tag releases were 

 from a trap located at the left ladder exit, and at 

 sites on both sides of the river about 1 mile above 

 the dam. 



Various tag colors or shapes were used for the 

 experiments at Rock Island Dam (fig. 5). Tags 

 applied in the forebay differed from those used 

 below the dam. Serially numbered plastic disks 

 in combination with plastic bars formed one series 

 of combinations, and serially numbered plastic 

 disks with vinyl tubing and vinyl-coated nylon 

 formed another series used below the dam. These 

 were attached to each fish by nickel pins inserted 

 through the body just below the dorsal fin. All 

 tags were applied in pairs so that the same color 

 or kind of tag showed on both sides of the fish. 

 During 1954-55, the salmon were tagged while 

 held in canvas-lined, cradle-type boxes. In 1956, 

 the boxes were filled with water and the salmon 

 were held under water during tagging. 



Fish counters at the dam identified and recorded 

 the tags as tagged fish crossed the counting boards. 

 Display boards containing all tag samples were 



340 



U.S. FISH AND WILDLIFE SERVICE 



