NOTES 



HOMING AND FISHERIES CONTRIBUTION 



OF MARKED COHO SALMON, 



ONCORHYNCHUS KISUTCH, RELEASED AT 



TWO COLUMBIA RIVER LOCATIONS 



In 1970 we conducted an experiment to deter- 

 mine if coho salmon, Oiieorhynchus kisutch, re- 

 leased away from the rearing site would return 

 to the release area and contribute to the fisheries 

 there (Vreeland et al. 1975). We found the coho 

 salmon returned almost exclusively to the re- 

 lease area and contributed to the fisheries near 

 the release site. However, because the single fin 

 marks applied were duplicated by other experi- 

 menters on the Pacific coast, we could not evalu- 

 ate the contribution of the two groups to the ocean 

 fisheries. We also surmised a possible detrimen- 

 tal effect of transportation on the survival of the 

 group released downstream from the hatchery. 

 In 1972 we initiated a study with 1971-brood 

 coho salmon to 1) confirm the homing results of 

 the previous study, 2) eliminate possible differ- 

 ences in survival due to transportation, and 3) 

 determine the contribution of the release groups 

 to the Pacific coast fisheries. 



Methods 



We chose coho salmon originally from Klaska- 

 nine Hatchery in Oregon, the same fish stock 

 used in the previous study. Hatchery personnel 

 collected adults and took eggs at Little White 

 Salmon National Fish Hatchery, located near 

 Cook, Wash., on the Little White Salmon River 

 about 1.5 km (1 mi) upstream from its confluence 

 with the Columbia River and 242 km (150 mi) 

 from the Pacific Ocean (Fig. 1). Coho salmon 

 were reared at Willard National Fish Hatchery, 

 4.5 km (3 mi) up the Little White Salmon River 

 from Little White Salmon Hatchery. 



The two groups offish were hatched and raised 

 under uniform conditions in hatchery ponds. Fin 

 clipping took place in September 1972 at Wil- 

 lard Hatchery. We applied two marks to the fish: 

 adipose right ventral (Ad-RV) and adipose left 

 ventral (Ad-LV). 



Youngs Bay (Fig. 1) was selected as the release 

 site, situated about 19 km (12 mi) upstream from 

 the mouth of the Columbia River and fed by four 

 small rivers: Lewis and Clark, Walluski, Youngs, 



and Klaskanine Rivers. We transported the Ad- 

 RV marked coho salmon 253 km (157 mi) in about 

 4 h to Youngs Bay on 14 and 15 May 1973, where 

 they were released at a public launch ramp. We 

 transported the fish in two tank trucks, each 

 3,785 1 (1,000-gal) capacity. Each truck was 

 loaded with 462 kg (1,018 lb) of fish at 57.8 fish/ 

 kg (26.2 fish/lb) or about 26,700 fish. During the 

 2 d, we transported 106,852 Ad-RV marked coho 

 salmon weighing 1,847 kg (4,072 lb) from Willard 

 Hatchery to Youngs Bay (Table 1). 



To maintain similar handling procedures and 

 equalize any possible effects of transportation on 

 survival, we transported the Willard Hatchery 

 release for a time and distance similar to the 

 Youngs Bay release. On 16 and 17 May 1973, we 

 hauled 107,707 Ad-LV marked coho salmon 

 weighing 1,835 kg (4,045 lb) in the same two tank 

 trucks used for the Youngs Bay release. The fish 

 were transported about 161 km (100 mi) for 3 h 

 and 35 min on 16 May and 182 km (113 mi) for 3 h 

 and 50 min on 17 May. Each truck contained 

 about 458 kg ( 1,010 lb) of coho salmon. The hatch- 

 ery crew released all the coho salmon from Wil- 

 lard Hatchery into the Little White Salmon 

 River on 17 May. 



We used catches of marked coho salmon in the 

 fisheries and hatchery return data to determine 

 the effect of release site on contribution and hom- 

 ing. Sampling for fin-marked coho salmon took 

 place in 1973 and 1974 in the major Pacific coast 

 salmon fisheries of Alaska, Washington, Oregon, 

 and California, the Columbia River fisheries, 

 and at potential hatchery return sites on the 

 Columbia River. State fishery personnel sampled 

 the Alaska troll fishery, the California, Oregon, 

 and Washington ocean sport and troll fisheries, 

 and the Columbia River gill net fishery. Person- 

 nel from National Marine Fisheries Service sam- 

 pled catches from the Youngs Bay gill net fishery 

 at two fish processing plants. 



Table 1.— Numbers of marked coho salmon released in the 

 Columbia River for the homing experiment. Ad-RV = adipose 

 right ventral; Ad-LV = adipose left ventral. 



FISHERY BULLETIN: VOL. 81. NO. 1. 1983. 



143 



