PEARCY and FISHER: MIGRATIONS OF COHO SALMON 



Table 4. — The percent of coho salmon jacks and males, by length groups, in the total catch, 



Augjst 1981 and September 1982-84. 



'Jack Is defined as a male whose testes wt. /total body wt. x 100 > 0.3% in August and >2.0% in Septem- 

 ber. 



Movements of Marked Fish 



Direct evidence of movements of juvenile coho 

 salmon was obtained from capture of marked fish 

 containing coded wire tags or marked with fluo- 

 rescent pigment. The generalized pattern of 

 movements that emerges for 1981-85 is an initial 

 movement of most juvenile coho salmon to the 

 south soon after ocean entry in May and June and 

 then a reversal of movement with most fish mi- 

 grating to the north by August and September 

 (Figs. 4-8). These trends are discussed for fish 

 originating from the Columbia River, Oregon 

 coastal, Washington coastal, and private hatch- 

 eries. 



Columbia River 



Juvenile coho salmon originating from hatch- 

 eries on the Columbia River were usually recov- 

 ered south of the Columbia River in May. This 

 trend was especially obvious in May 1982 when 

 all 22 marked fish which were recovered moved 

 south, some as far as 175 km (Fig. 5). In May 

 1981, all but one of 14 marked Columbia River 

 fish were caught to the south, three as far as 180 



and 204 km (Fig. 4). In May 1983, all four fish 

 were taken south of the mouth of the Columbia 

 River (Fig. 6). 



During June and July of all years, marked Co- 

 lumbia River coho salmon were recovered in 

 nearly equal proportions both north and south of 

 the river mouth, except in June 1982 when 15 of 

 17 fish were found to the south (Figs. 4—8). By 

 September, all marked Columbia River coho 

 salmon were captured north of the river, includ- 

 ing fish captured off the Quinault River in Sep- 

 tember 1982 and off Cape Flattery in September 

 1984. Fish were also caught close to the mouth of 

 the Columbia River in July, August, and Septem- 

 ber, indicating that some marked juvenile coho 

 salmon did not undertake extensive migrations at 

 sea. 



In two sets on the Wecoma Beach Transect on 1 

 June 1982 we caught 17 marked juvenile coho 

 salmon released between 30 April and 6 May 

 from six hatcheries on the Columbia River. Based 

 on downstream migration rates for these groups 

 to Jones Beach (Dawley et al. 1985) and assuming 

 similar rates from Jones Beach to the ocean, these 

 fish had probably been in the ocean for <10 days 

 before recapture. This indicates that some juve- 



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