CONTRIBUTION OF WILD AND HATCHERY-REARED COHO SALMON, 

 ONCORHYNCHUS KISUTCH, TO THE OREGON OCEAN SPORT FISHERY 



Dennis L. Scarnecchia' and Harry H. Wagner^ 



ABSTRACT 



Eight scale characters of known hatchery and wild coho salmon. Oncorhynchus kisutch, were com- 

 pared, and a 1 inear discrimmant function was used to determine whether hatchery and wild adult coho 

 salmon could be reliably separated on the basis of scale characteristics. Attempted separation was 

 based upon known differences in rearing environments of hatchery and wildjuvenile coho salmon and 

 upon hatchery smolts being larger than wild smolts. Identifications were correct for 82'7t of the 

 hatchery fish and 89<7r of the wild fish. Based on analysis of scales from adult coho salmon of unknown 

 origin (hatchery or wildl and the estimated catch of marked, hatchery-reared coho salmon taken by the 

 Oregon sport fishery . we concluded that TSVr of the fish caught in the ocean along the Oregon coast from 

 mid-June to mid-September 1977 had been released as smolts from hatcheries. Percentages of hatchery 

 fish in the catch ranged from 85 near the mouth of the Columbia River to 61 at Winchester Bay on the 

 central Oregon coast , Fisheries along the south and central Oregon coast may have had access to higher 

 percentages of wild coho salmon after mid-August than prior to this time, probably because wild fish 

 from coastal streams remained near these ports, whereas most fish destined for Columbia River 

 hatcheries had already migrated northward. 



The coho salmon, Oncorhynchus kisutch. is the 

 most abundant species of salmon contributing to 

 Oregon's commercial troll and ocean recreational 

 fisheries (Oregon Department of Fish and 

 Wildlife^). Numbers of this species caught com- 

 mercially in Oregon have historically fluctuated 

 widely. Catches from 1952 to 1962 averaged 

 292.000 fish and ranged from 551,000 in 1957 to 

 112,000 in 1960, Numbers of coho salmon caught 

 increased generally in 1963-77 and averaged 

 860,000 fish/yr while ranging from 1,827,000 in 

 1976 to 450,000 in 1977. Catches by the 

 Washington and California troll fisheries have 

 also increased in recent years (Wright 1976; 

 Pacific Fishery Management Council 1978), This 

 rise in catch has been attributed to increased pro- 

 duction by Federal and state hatcheries of larger 

 and healthier smolts (Pacific Fishery Manage- 

 ment Council 1978; Reed"). 



'Oregon Cooperative Fishery Research Unit (cooperators are 

 the Oregon Department of Fish and Wildlife. U,S, Fish and 

 Wildlife Service, and Oregon State University). Oregon State 

 University. Corvallis. Oreg,; present address: Colorado Coopera- 

 tive Fishery Research Unit. Colorado State University. Fort 

 Collins. CO 80523, 



K)regon Department of Fish and Wildlife, Corvallis. OR 

 97331, 



^Oregon Department of Fish and Wildlife, 1977 unpubl, stat, of 

 troll salmon investigations group. Marine Science Drive. Bldg 

 #3. Newport. OR 97365, 



•■Reed. P, H, 1976. A history and current status of Oregon 

 ocean salmon fisheries-troll salmon investigations, Oregon 



This increased abundance of coho salmon has 

 coincided with, and partly led to, the development 

 of a substantial sport fishery in the ocean off Ore- 

 gon, Washington, and California, The number of 

 coho salmon caught in the ocean by sport fisher- 

 men has been fairly stable in Oregon since 1964 

 but has increased rapidly in Washington since the 

 early 1960"s (Phinney and Miller 1977; Pacific 

 Fishery Management Council 1978), 



Although both total releases of coho salmon 

 smolts from public hatcheries and catch have in- 

 creased, indices of escapement of wild fish indicate 

 that the numbers of wild coho salmon spawning 

 have decreased (Cummings-'^). In an analysis of 

 counts of spawning salmon from selected areas of 

 eight Oregon coastal streams from 1964 to 1974, 

 we found that counts of adult salmon have de- 

 clined significantly in the Nestucca (P-O.Ol), 

 Alsea (P<0.01), Yaquina (P<0.05), and Coquille 

 (P<0.005) Rivers and Beaver Creek (P<0.05), but 

 no significant trends were observed in the 

 Nehalem, Wilson, and Coos Rivers. For all spawn- 

 ing areas combined, the conclusion is that overall 

 escapements are declining (P- 0.01) on coastal 



Manuscript accepted M.irch 1979 



FISHERY BULLETIN: VOL, 77, NO, 3. 1980, 



Department of Fish and Wildlife. Marine Science Drive. Bldg, 

 #3, Newport. OR 97365, 



^Cummings. E 1977, Spawning coho and chinook salmon 

 surveys in coastal watersheds of Oregon, 1976, Oregon De- 

 partment of Fish and Wildlife. 17330 SE Evelyn Street, Clac- 

 kamas. OR 97015. 



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