sively to the area of release, similar to fish in pre- 

 vious studies (Rounsefell and Kelez 1938; Taft 

 and Shapovalov 1938; Donaldson and Allen 1957; 

 Ellis 1968 1 ; Jensen and Duncan 1971; Mahnken 

 and Joyner 1973; Vreeland et al. 1975; Scholz et 

 al. 1976). No Willard Hatchery release fish were 

 caught in the Youngs Bay fishery, but 199 

 Youngs Bay release fish were caught in the fish- 

 ery. Only two Youngs Bay releases were seen in 

 hatchery returns, one at Klaskanine Hatchery 

 and the other at Little White Salmon Hatchery 

 (Table 2). Hatchery personnel observed only 26 

 Willard releases at Little White Salmon Hatch- 

 ery. Construction in 1974 of a new barrier dam 

 and fish ladder at the hatchery may have pre- 

 vented some coho salmon from entering the 

 hatchery ponds. However, the hatchery biologist 

 at Little White Salmon Hatchery believed most 

 fish entered the adult holding ponds prior to the 

 ladder closure. 2 



The specificity of the homing we observed is 

 apparently linked to the physiological stage of 

 parr-smolt transformation. Work by Hasler 

 (1966) and Carlin(1968) indicated the imprinting 

 process occurs rapidly at the time of parr-smolt 

 transformation. With steelhead trout, Salmo 

 gairdneri, Wagner (1969) hypothesized the hom- 

 ing imprint is acquired rapidly before and/or 

 during downstream migration. Mighell (1975) 3 

 found fish exposed to a new water source for as 

 little as 4 h will imprint on the new source. Coho 

 salmon released in a Lake Michigan tributary 

 strayed extensively (Peck 1970). Hasler et al. 

 (1978) postulated that this was due to releasing 

 the fish after smolting had taken place. Jensen 

 and Duncan (1971) described accurate homing 

 with coho salmon released afsmolt size." Cooper 

 et al. (1976) found a 2-d exposure to morpholine 

 at the onset of smolting imprinted fish to the 

 chemical as well as did a 30-d exposure. W. S. 

 Zaugg (1975), 4 who has attempted to define more 



Table 2.— Number of 1971-brood Youngs Bay and Willard 

 Hatchery release coho salmon recovered at five Columbia 

 River hatcheries. 1973 and 1974. Ad-RV = adipose right ven- 

 tral; Ad-LV = adipose left ventral. 



'Ellis, C. H. 1968. A return of adult coho salmon demon- 

 strating a high degree of selectivity in homing, In Proceed- 

 ings of the Northwest Fish Culture Conference, December 4-6, 

 1968, Boise, Idaho, p. 40-42. Unpubl. manuscr. Wash. Dep. 

 Fish., 115 Gen. Admin. Bldg., Olympia, WA 98504. 



2 S. L. Leek, U.S. Fish and Wildlife Service, Little White 

 Salmon National Fish Hatchery, Willard, WA 98605, pers. 

 commun., September 1978. 



3 Mighell, J. 1975. Some observations on imprinting of ju- 

 venile salmon in fresh and saltwater. In Summary notes from 

 papers presented at homing workshop. Unpubl. manuscr., 

 p. 11-12. Northwest and Alaska Fish. Cent., Natl. Mar. Fish. 

 Serv., NOAA, 2725 Montlake Blvd. E.. Seattle, WA 98112. 



4 W. S. Zaugg, Northwest and Alaska Fisheries Center, Na- 

 tional Marine Fisheries Service, NOAA, 2725 Montlake Blvd. 

 E., Seattle, WA 98112, pers. commun., November 1975. 



closely the onset of the parr-smolt transforma- 

 tion, feels the imprinting will not occur until a 

 certain stage of the transformation is reached. 

 Unfortunately, none of the authors (nor do we) in- 

 dicate a stage of the parr-smolt transformation 

 at time of release. Time of smolting and imprint- 

 ing has yet to be defined closely enough to predict 

 the homing location of fish released in different 

 areas. Until more is learned, we expect varying 

 results could occur with homing studies depend- 

 ing on when the fish are released. 



Fishery Contribution 



We examined ocean and Columbia River 

 catches of coho salmon to determine the contri- 

 bution of both release groups to the Pacific coast 

 fisheries. Fishery samplers saw 350 Youngs Bay 

 releases and 78 Willard releases in 1973 and 1974 

 (Table 3). No coho salmon from either release 

 were observed in the catches of Alaska commer- 

 cial fisheries. Fisheries samplers in Canada did 

 not examine coho salmon for multiple fin marks; 

 however, on the average, Canadian fishermen 

 land only 6% of all Columbia River hatchery coho 

 salmon (Wahle et al. 1974). Catches of the two 

 marked groups occurred primarily in the Wash- 

 ington, Oregon, and California marine fisheries 

 and the Columbia River gill net fishery. 



Total estimated catches for 1973 and 1974 of 

 Youngs Bay and Willard release groups are 2,455 

 and 598, respectively. Catches in the Oregon and 

 California troll fisheries contained over 50% of 

 both marked groups (55% Ad-RV, Youngs Bay 

 and 61% Ad-LV, Willard releases). Washington 

 marine recoveries occurred primarily near the 

 Columbia River, except for catches of Willard re- 

 lease coho salmon at LaPush on the north Wash- 

 ington coast. Landings of Willard release fish at 

 LaPush comprised nearly one-half of the release 

 caught in the Washington troll fisheries. 



145 



