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Fishery Bulletin 102(1) 



about one half of the nonjacks caught north of Cape Blanco 

 in August were hatchery fish. 



Two factors, however, may have lead to inaccuracies in 

 estimation of hatchery-wild ratios of coho salmon in the 

 GLOBEC study area. First, because of low sample sizes, 

 the data were pooled from both June and August catches 

 for the genetic stock analysis; therefore we do not know the 

 proportional contributions of the different release areas 

 to the catches in either month alone. Second, all the fish 

 released from Klamath River and Trinity River hatcheries 

 had been clipped on the maxillary. We were unaware that 

 the maxillary clip was being used, did not look for it, and 

 consequently may have classified fish with this mark as 

 unmarked. Therefore, the proportion of hatchery fish in 

 the catch of coho salmon during GLOBEC may have been 

 higher than is shown in Table 3. 



Age and growth of juvenile coho salmon 



Forty-three percent (24 of 56) of the juvenile coho salmon 

 caught during the August GLOBEC cruise were preco- 



cious males ("jacks") according to the testes-weight to 

 body-weight criteria of Pearcy and Fisher ( 1988). This is a 

 much higher percentage of jacks than found among juve- 

 nile fish caught in September 2000 in the plume study off 

 Oregon and Washington, where only 4.5% offish (6 of 132) 

 were precocious males or females according to the same 

 criteria. Because the jacks were considerably larger than 

 the nonjacks, average growth rates of the two groups were 

 reported separately. 



Estimated average growth rates in FL between ocean 

 entry and capture were higher for fish caught in the 

 August 2000 GLOBEC cruises (1.56-2.22 mm/d) than 

 for fish caught in any other cruises (Table 3). The fish 

 caught in August 2000 were also larger when they entered 

 the ocean (average 170- 178 mm FL) than fish caught in 

 other cruises (averagel54-160 mm FL). Average growth 

 rate of jacks from north of Cape Blanco (2.22 mm/d), was 

 significantly higher (/-test, P<0.05) than growth rates of 

 nonjacks (1.56-1.67 mm/d). Growth rates of nonjacks north 

 and south of Cape Blanco were not significantly different la- 

 test, P<0.05). The combination of large size at ocean entry 



