MAJOR and PAILIK: ENCROACHMENT OK WANAPl M D.VM RESERVOIR 



25r 



LEFT-BANK 

 RELEASE AREA 



— • 1954 

 — O 1955 



* » 1964 



A A 1965 



RIGHT- BANK 

 RELEASE AREA 



I II III IV V 



RELEASE PERIOD 



M III IV 



RELEASE PERIOD 



Figure 5. — Time required for tagged sockeye salmon 

 to move over the Rock Island Dam fish ladders from 

 the tagging areas below the dam, 1954, 1955, 1964, 

 and 1965. 



SUMMARY AND CONCLUSIONS 



The lower portions of the fish ladders at Rock 

 Island Dam were flooded by the reservoir of 

 Wanapum Dam. At the direction of the Federal 

 Power Commission, the fish ladders were mod- 

 ified to maintain or enhance fish passage and a 

 study was developed to evaluate the adequacy 

 of the modifications. 



In 1964 and 1965 over 2,000 spring- chinook 

 and sockeye salmon were tagged and released 

 below Rock Island Dam; their subsequent move- 

 ment over the fish ladders w^as noted. Three 



features — travel time, the percentage of tagged 

 fish observed, and the distribution of tagged fish 

 by ladder — were compared with data obtained 

 in a similar tagging study in 1954 and 1955. 



Results clearly indicate that the fish passage 

 over Rock Island Dam was better in 1964 and 

 1965 than in 1954 and 1955. Travel times were 

 significantly shorter and higher percentages of 

 tagged fish were sighted passing over the ladders 

 under postencroachment conditions. 



LITERATURE CITED 



Dunn, 0. J. 



1961. Multiple comparison among means. J. Am. 

 Stat. Assoc. 56(293) : 52-64. 

 Fisn, F. F., AND M. G. Hanavan. 



1948. A report upon the Grand Coulee fish-mainte- 

 nance project 1939-1947. U.S. Fish Wildl. Serv., 

 Spec. Sci. Rep. 55, 63 p. 

 French, R. R., and R. J. Wahle. 



1966. Study of loss and delay of salmon passing 

 Rock Island Dam, Columbia River, 1954-56. U.S. 

 Fish Wildl. Serv., Fish. Bull. 65: 339-368. 



Koo, T. S. Y., AND A. Isarankura. 



1967. Objective studies of scales of Columbia River 

 chinook sa.\rtwn, Oncorhynchus tshawytsclia (Wal- 

 baum). U.S. Fish Wildl. Serv., Fish. Bull. 66: 

 165-180. 



LEMAN, B., AND G. J. Paulik. 



1966. Spill pattern manipulation to guide migrant 

 salmon upstream. Trans. Am. P^ish. Soc. 95 : 

 397-407. 

 Thompson, W. F. 



1945. Effect of the obstruction at Hell's Gate on 

 the sockeye salmon of the Fraser River. Int. 

 Pac. Salmon Fish. Comm., Bull. 1, 175 p. 



140 



