Brodeur et al.: Distribution, growth, condition, origin, and associations of juvenile salmonids 



43 



E 



o 



•Chinook 1 

 Coho 1 .0 

 -Habitat 



12 14 



Water temperature (C) 



10 15 



Chla concentration 



1 



09 

 08 

 07 

 06 

 0.5 

 04 

 03 

 0.2 

 1 





 31.50 



3250 3300 



Salinity (PSU) 



•Chinook 1 

 -Coho 1.0 

 -Habitat 



100 150 200 



Water depth (m) 



Figure 9 



Cumulative distribution curves for salmon and environmental or station variables. Only the August variables that showed at least 

 one significant difference are included. See Table 8 for results of the statistical tests. 



from these rivers are known to primarily migrate north 

 of our study area along the coast (Nicholas and Hankin, 

 1988). By August, fish from these stocks were nearly absent 

 from our samples. Oregon rivers south of Cape Blanco, an 

 area that includes the Rogue, Chetco, and Winchuck riv- 

 ers, produce chinook salmon with a more southerly pattern 

 of ocean migration (Nicholas and Hankin, 1988; Myers et 

 al., 1998). Chinook salmon from these rivers were found 

 throughout the summer and contributed 53% to our largest 

 catches of chinook salmon along transects south of Cape 

 Blanco in August. 



Results from our 2000 GLOBEC cruises identified Cape 

 Blanco as an important breakpoint in salmonid life-his- 

 tory variation. Stock distributions of both juvenile salmon 

 and steelhead indicated that different migration patterns 

 of fish originating from southern and northern rivers are 

 evident during their early marine phase. Our August sur- 

 vey also revealed sharp contrasts in life-history type and 

 freshwater origin between the juvenile chinook salmon 

 population in the marine area north of Cape Blanco and 



that to the south. Chinook salmon captured north of Cape 

 Blanco were nearly all yearlings and largely from the Sac- 

 ramento River drainage. Subyearlings predominated in our 

 catches south of Cape Blanco and included a much larger 

 proportion offish from coastal streams in southern Oregon 

 and northern California. 



Comparisons of our results with similar studies conduct- 

 ed further north show differences in salmonid migrations 

 on a somewhat broader geographic scale. In several years of 

 sampling during the summers of 1981 through 1985 off the 

 central Oregon to northern Washington coast, most juvenile 

 chinook salmon bearing CWTs were from Columbia River 

 hatcheries (Pearcy and Fisher, 1990; Fisher and Pearcy, 

 1995). Only one tagged chinook salmon from a river south 

 of Cape Blanco (Klamath River) was captured. Pearcy and 

 Fisher also found that juvenile coho salmon were largely 

 from the Columbia River and that smaller contributions 

 were from coastal rivers north of Cape Blanco. Their find- 

 ings have been corroborated by more recent surveys in the 

 same region (Emmett and Brodeur, 2000) using genetic 



