Adult returns indicate a definite benefit is 

 achieved from transporting juvenile chinook salm- 

 on and steelhead trout from a collector dam (Ice 

 Harbor) to a release site below Bonneville Dam. 

 Transport benefits were lower than reported from 

 releases made in 1968, but a benefit of 27-47% was 

 still indicated. No steelhead trout were released at 

 Bonneville Dam in 1969, but a 47% benefit was 

 realized from transportation of juveniles to that 

 site in 1970. 



Data from returning adults indicate that in 

 general the John Day release site was a poor one. 

 In 1969, however, returns from juvenile steelhead 

 trout releases there were 174% greater than con- 

 trols. The reduced transport benefit for our John 

 Day release can probably be best explained by the 

 fact that juveniles must still pass over The Dalles 

 and Bonneville dams before entering the ocean. 

 These further stresses probably nullify any initial 

 transport benefit. 



The rate of adult return from those juvenile fish 

 transported in 1969 was better than the adult re- 

 turns from those transported in 1970. Data sug- 

 gest that stresses to juveniles encountered prior 

 to collection at Ice Harbor and the changed 

 handling procedures in 1970 were a factor. 



Literature Cited 



Bentley, W. W., and H. L. Raymond. 



1969. Passage of juvenile fish through orifices in gatewells 

 of turbine intakes at McNary Dam. Trans. Am. Fish. See. 

 98:723-727. 

 DuRKiN, J. T., W. J. Ebel, and J. R. Smith. 



1969. A device to detect magnetized wire tags in migrating 

 adult coho salmon. J. Fish. Res. Board Can. 26:3083-3088. 

 Ebel, W. .J., D. L. Park, and R. C. .Johnsen. 



1973. Effects of transportation on survival and homing of 

 Snake River chinook salmon and steelhead trout. Fish. 

 Bull., U.S. 71:.549-.563. 

 Jefferts, K. B., p. K. Bergman, and H. F. Fiscus. 



1963. A coded wire identification system for macro-or- 

 ganisms. Nature (Lond.) 198:460-462. 

 MiGHELL, J. L. 



1969. Rapid cold-branding of salmon and trout with liquid 

 nitrogen. J. Fish. Res. Board Can. 26:2765-2769. 

 Park, D. L., and W. E. Farr. 



1972. Collection of juvenile salmon and steelhead trout 

 passing through orifices in gatewells of turbine intakes at 

 Ice Harbor Dam. Trans. Am. Fish. Soc. 101:.381-384. 



Emil Slatick 



Donn L. Park 



VFesley J. Ebel 



Northiret^t Fisheries Center 



National Marine Fisheries Service, NOAA 



2725 Montlake Bouleva rd East 



Seattle. WAD8112 



COMPARATIVE VULNERABILITY OF FRY OF 



PACIFIC SALMON AND STEELHEAD TROUT 



TO PREDATION BY TORRENT SCULPIN 



IN STREAM AQUARIA 



Predation on fry of salmon and trout by sculpin, 

 Cottuii spp., is intense in certain situations 

 (Hunter 1959; Sheridan and Meehan 1962; Patten 

 1962, 1971a, 1972) or of little consequence in others 

 (Ricker 1941; Patten 1971a, 1972). Variation in in- 

 tensity may be related to such important causes as 

 the environment or to specific differences of the 

 predators or prey. 



In this paper I report the comparative ability of 

 steelhead trout, Salmo gairdneri, and of five 

 species of Pacific salmon, Oncorhynchus spp., to 

 avoid predation by torrent sculpin, C. rhofheus, in 

 a fixed environment-stream aquaria. The 

 vulnerability of a species of salmon or steelhead 

 trout, as determined from this study, is related to 

 known information on the duration of residency 

 and behavior of a species in streams. These results 

 help in the assessment of natural causes of mor- 

 tality that affect the productivity of salmon and 

 steelhead trout. The study was conducted in 

 stream aquaria adjacent to Cedar River near 

 Ravensdale, Wash., in 1966. 



Facilities and Procedures 



The facilities consisted of two stream aquaria 

 and eight holding aquaria that received water 

 from the Cedar River (more fully described by 

 Patten 1971b). Two stream aquaria used for tests 

 of predation were 2.4 m long and 0.6 m wide and 

 high; water depth ranged from 2 to 18 cm depend- 

 ing on bottom contour. The eight holding aquaria 

 used in the study (to incubate the eggs and main- 

 tain the young fish before tests) were 34 cm wide 

 by 41 cm long by 36 cm high; water depth was 18 

 cm. 



Water from the Cedar River was taken at a low 

 dam and supplied by gravity flow to the head box 

 and then to the stream aquaria. Each aquarium 

 had a continuous flow. The water was usually clear, 

 and temperatures recorded at 0800 ranged from 5° 

 to 10°C during the course of the study. 



The experimental procedure exposed salmon or 

 trout fry to predation by torrent sculpin under 

 pseudo-natural but controlled conditions. Torrent 

 sculpin were collected by electrofishing in Soos 

 Creek, Wash.; the salmon and steelhead trout fry 

 were reared from eggs to insure that they had no 

 previous experience with predators. 



931 



