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



33 



45.0 



44.5 



44.0 



43.5 



43.0 



42.5 



42.0 



41.5 



Newport 



Oregon 

 r California 



45.0 



44.5 



44.0 



43.5 



43.0 



42.5 



42.0 



41.5 



125.5 



125.0 



124.5 



124,0 



123.5 125.5 

 Longitude (W) 



125.0 



124.5 



124.0 



123.5 



Figure 3 



Catch distribution for juvenile coho (Oncorhynchus kisutch) and chinook salmon (O. tshawytscha) 

 for the (A) June and (B) August cruise overlaid on surface temperature contours. Plus signs are 

 stations sampled where no salmon were caught. 



and favorable conditions for growth in the ocean probably 

 contributed to the very high percentage of jack coho salmon 

 in August 2000 in the GLOBEC study area. 



Estimated average growth rates between ocean entry and 

 capture of juvenile coho salmon were higher in the GLOBEC 

 area than in the plume study area U-tests, P<0.05). For fish 

 caught in June, average growth rate was 1.06 mm/d and 0.63 

 mm/d in the GLOBEC and plume study areas, respectively. 

 For fish caught in August or September, average growth 

 rate was 1.57-2.22 mm/d in the GLOBEC study area and 

 1.17 mm/d plume in the study area (Table 3). The higher 

 growth rates of coho salmon caught in the GLOBEC study 

 area suggests that in 2000 conditions for growth were bet- 

 ter there than those in the plume study area farther north 

 off Oregon and Washington. Average instantaneous growth 

 rates in weight were also higher (/-tests, P<0.05) for the 

 fish caught in the June and August 2000 GLOBEC cruises 

 (2.0 and 2.1-2.8% body wt/d, respectively) than for the fish 

 caught in the June and September 2000 plume study cruises 

 (1.2 and 1.7 % body wt/d, respectively; Table 4A). 



In addition, the average condition index (CI) of juve- 

 nile coho salmon in June was significantly higher (/-test, 



P=0.03) in the GLOBEC study area (1.12, n=32, SD=0.087) 

 than in the plume study area (1.07, n=245, SD=0.117). 

 Similarly, the average CI of nonjack juvenile coho salmon 

 was higher (/-test, P=0.002) in August in the GLOBEC 

 study area (1.24, n=32, SD=0.096) than in September in 

 the plume study area (1.18, n=132, SD=0.100). Both the 

 high instantaneous growth rates in weight and the high 

 CI of juvenile coho salmon caught in the GLOBEC study 

 area suggest that conditions for growth of coho salmon in 

 this area were very good in 2000. Growth rates estimated 

 from the few CWT fish caught during these cruises (Table 

 4B) were similar to, and help validate, the growth rates 

 estimated from scales (Table 4A). 



Average weights at time of ocean entry back-calculated 

 from scales for coho salmon caught in June in the GLOBEC 

 area and in all months in the plume study area (Table 4A) 

 were slightly higher than the average weights of hatchery 

 coho salmon at time of release (Appendix Table 1). For ex- 

 ample, in the plume study area, average back calculated 

 weights at ocean entry ranged from 37.5 g to 42.4 g (Table 

 4A) — slightly higher than the expected average weights 

 at release of about 32-33 g based on the stock composi- 



