FISHERY BULLETIN: VOL. 87, NO. 3, 1989 



1971) than smaller prey, such as harpacticoid 

 copepods. Volk et al. (1984) reported that food 

 conversion efficiency was much higher for juven- 

 ile chum salmon fed harpacticoid copepods than 

 larger amphipods. All these factors could affect 

 growth. Furthermore, pelagic calanoid cope- 

 pods, hyperiid amphipods, and larvaceans, 

 known to be important prey for large (>45 mm) 

 juvenile chum salmon as they move to open 

 neritic waters (Simenstad and Salo 1980), were 

 not abundant in Netarts Bay, perhaps further 

 constraining growth and production in this small 

 estuary. 



A possible strategy to circumvent the need for 

 estuarine rearing where habitat quality limits 

 production is to release juvenile chum salmon at 

 a large size. Healey (1980a, 1982a) observed that 

 seaward movement of juvenile chum salmon is 

 size-dependent, with large fish moving offshore 

 first. Juvenile chum salmon entering estuaries 

 late in the spring also emigrate after a short time 

 (Sibert et al. 1977; loka 1978). In Japan, juvenile 

 chum salmon reared in salt water (Kobayashi 

 1980) migrate to the open sea within a week after 

 release and chum salmon reared to a large size (8 

 g) return to hatcheries at a high rate (loka 

 unpubl. data). 



Our experimental releases of different sizes of 

 fry indicate that large juvenile chum salmon do 

 not utilize Netarts Bay as a nursery area. The 

 large (6.5 g) chum we released in 1986 appar- 

 ently migrated immediately to the ocean. When 

 these fish returned to Whiskey Creek as adults 

 in 1988 (presumably at age 3, based on the age 

 structure of previous runs (Lannan 1983; J. 

 Fisher unpubl. data)), the ratio offish with miss- 

 ing left: right ventral fins was 2:1 (W. McNeil, 

 pers. commun."*). This ratio was 0.6:1 in the 

 juvenile chum salmon released in 1986 (Table 1). 

 This suggests that these large (6.5 g) juvenile 

 chum salmon that were not dependent on the 

 estuary survived at rates that were 3-4 times 

 higher than the smaller (1.(^2.2 g) fish released 

 that year. More experiments are needed to con- 

 firm these results. Rearing chum salmon fry to a 

 large size may be a useful method to enhance 

 hatchery runs into estuaries, especially if size- 

 selective predation is intensified by retarded 

 growth owing to high temperatures or low avail- 

 ability of prey. Furthermore, large hatchery fish 



■"W. McNeil, Oregon State University, Hatfield Marine 

 Science Center, Newport, OR 97.365, pers. commun., 5 De- 

 cember 1988. 



released late in the spring may have minimal 

 adverse impacts on wild stocks. 



ACKNOWLEDGMENTS 



This research was supported by the Oregon 

 State University (OSU) Sea Grant College Pro- 

 gram (Grant No. NA 85-AA-D-SG 095, Project 

 R/EM-13), the Northwest Alaska Fisheries Cen- 

 ter (Contract 84-ABC-0009 and NA-85-ABN- 

 00025), and Oregon Aqua-Foods, Inc. We thank 

 M. Wilson, M. Bauwman, F. Ratti, R. Brodeur, 

 B. Burkle, A. Chapman, R. Chitwood, M. Duffy, 

 J. Fisher, L. Jang, K. Krefft, P. Lamberson, L. 

 Mahn, and E. Rexstad for their invaluable assis- 

 tance in the field; D. Miller (Oregon Department 

 of Fish and WildHfe (ODFW)), for the use of a 

 boat; H. Frolander and P. Kalk (OSU College of 

 Oceanogi'aphy), R. Tubb (OSU Department of 

 Fisheries and Wildlife (DFW)), R. Irish 

 (ODFW), and R. Swartz (U.S. Environmental 

 Protection Agency (USEPA), Hatfield Marine 

 Science Center (HMSC)) for the loan of boats and 

 motors; Hiram Li (OSU, DFW) for the use of a 

 tow net; R. Chitwood and L. Poole (Oregon 

 Aqua-Foods, Inc.) for the loan of net pens and 

 for rearing large chum fry. Marilyn Guin 

 (HMSC) provided extensive help on biblio- 

 graphic references, Lavern Weber (HMSC) pro- 

 vided laboratory space and facilities at HMSC, 

 and J. Lannan (HMSC) and K. Hopkins (OSU, 

 DFW) provided space at the Whiskey Creek 

 Hatchery necessary to conduct this research. 

 Bryan Coleman (USEPA, HMSC) provided 

 assistance with computers. S. Philhps (OSU, 

 DFW) helped both at the hatchery and in the 

 field. We also thank A. Schoener, M. Healey, W. 

 McNeil, C. Simenstad, and two anonymous 

 reviewers for comments on the manuscript. 



LITERATURE CITED 



Bailey, J. E., B. L. Wing, and C. R. Mattson. 



1975. Zooplankton and abundance and feeding habits 

 of fry of pink salmon, Oncorhi/tichus gorbuscha, and 

 chum salmon. Oncorhynchus keta, in Traitors Cove, 

 Alaska, with speculations on the carrying capacity of 

 the area. Fish. Bull., U.S. 73:846-«61. 

 Bax, N. J. 



1982. Seasonal and annual variations in the movement 

 of juvenile chum salmon through Hood Canal, Wash- 

 ington. In E. L. Brannon and E. 0. Salo (editors), 

 Salmon and trout migratory behavior symposium, p. 

 208-218. Univ. Wash., Seattle. 



1983. Early marine mortality of marked juvenile chum 

 salmon (Oncorhynchus keta) released into Hood Canal, 

 Puget Sound, Washington, in 1980. Can. J. Fish, 



566 



