adjustments will be limited if stocks experienc- 

 ing one environmental condition are continually 

 mixed with stocks undergoing different en- 

 vironmental factors. FOr this reason, it may 

 be desirable to release reared fingerlings only 

 at Spring Creek Hatchery and find a different 

 location for the release of fry. At a station 

 for releasing fry, it might be desirable to have 

 a constant temperature water source near 

 45 F., with pumped Columbia River water 

 available for gradually acclimating the fry 

 before release. Returning adults would require 

 trapping facilities that would minimize stray- 

 ing. Whether or not transfers from Spring 

 Creek Hatchery should be as eggs or as fry 

 needs to be studied, Carson DefX)t Springs 

 located on the Washington shore of the Columbia 

 River a few miles above Bonneville Dam is at 

 present being developed by the U.S. Fish and 

 Wildlife Service and should satisfy the require- 

 ments reasonably well. As an experimental 

 station, Carson Depot Springs might be of 

 value in the study and development of pro- 

 cedures best suited for the release of fry, 



Brett (1952) has shown that juvenile chinook 

 salmon will consistently orient themselves with 

 respect to temperature. Brett (1956, p, 85) 

 further states that "sensitivity to small gradi- 

 ents of temperature may act as a directive 

 factor." If migrating juvenile salmon pass 

 through a temperature gradient in entering a 

 large river like the Columbia River from a 

 relatively small tributary it is not unlikely 

 that some time will be spent in a relatively 

 small portion of the area containing this 

 temperature gradient. Large concentrations of 

 fry could collect in such areas even in tribu- 

 taries with natural spawning, but particularly 

 in hatchery streams where large releases are 

 made. Probable effects of predation are self 

 evident. We suggest that a study be made of 

 streams with natural runs as well as hatchery 

 streams to observe the time and manner in 

 vv'nch try pass through such areas of tempera- 

 ture gradient. Possible effects of predation 

 should be investigated. 



ACKNOWLEDGMENTS 



In a study of this nature the cooperation and 

 assistance of many organizations and individ- 



uals are required. The authors are indebted to 

 these organizations and individuals who helped 

 to make this report possible through their kind 

 aid and assistance; U.S. Fish and Wildlife 

 Service, with a special acknowledgment to 

 Clyde Adams, Floyd Anders, Irvin Brock, 

 Harlan Johnson, Alphonse Kemmerick, 

 L. E. Perry, A. J. Ross, Edna Wood, and Paul 

 Zimmer; Oregon Fish Commission; Wash- 

 ington State Department of Fisheries, with 

 special consideration to Richard Noble; Allyn 

 Seymour of the University of Washington; 

 Fisheries Research Institute, particularly to 

 R. L. Burgner, M. B. Dell, Ted S. Y. Koo, 

 J. F. Roos, and W. F. Royce. 



LITERATURE CITED 



BRETT, J. R. 



1941. Tempering versus acclimation in the 

 planting of speckled trout. Trans- 

 actions of the American Fisheries 

 Society, vol. 70, p. 397-403. 



1952. Temperature tolerance in young 

 Pacfic salmon, genus Oncorhynchus. 

 Journal of the Fisheries Research 

 Board of Canada, vol. 9, no. 6, 

 p. 265-323. 



1956, Some principles in the thermal re- 

 quirements of fishes. The Quarterly 

 Review of Biology, vol. 31, no. 2, 

 p. 75-87. 



BURROWS, ROGER E., DAVID D. PALMER, 



H. WILLIAM NEWMAN, and ROBERT L. 



AZEVEDO, 



1952. Tests of hatchery foods for salmon 



1951. U.S. Fish and Wildlife Service, 



Special Scientific Report — Fisheries 



No, 86. 24 p. 



ROBINSON, LESLIE A., DAVID D. PALMER, 



and ROGER E. BURROWS. 



1951. Tests of hatchery foods for blueback 



salmon 1949, U.S. Fish and Wildlife 



Service, Special Scientific Report — 



Fisheries No. 60, 21 p. 



20 



