Fisher and Pearcy: Seasonal changes in growth of Oncorhynchus kisutch off Oregon and Washington 



43 



Late April-Early May release — July recovery 



060 - 



0.055 - 



0.050 



0.045 H 



0.040 



0.035 



0.030 



0.5 



2.0 



060 

 0.055 

 0.050 

 0.045 

 0.040 - 

 0.035 - 

 030 



84-85. n = 27 



85-86, n = 54 



0.0 



0.5 



— I — 

 1.0 



2.0 



2.5 



0060 

 0.055 

 0.050 

 0.045 

 0.040 

 0.035 

 0.030 



1 1 1 1 1 



00 05 1.0 1.5 20 25 



Mean scale radius (mm, OE = 0) 



Figure 5 



Profiles of changing average circulus spacing (±2 SE) versus 

 average scale radius at 50 intervals along the axis of mea- 

 surement (see "Methods and Materials" section) for matur- 

 ing coho salmon (O. kisutch) caught in the ocean fisheries 

 and (A) released as smolts from hatcheries in late April 

 or early May and caught in July, (B) released in March, 

 (C) released in late May or early June and caught late 

 June to late July, (D) unmarked maturing fish caught in 

 research nets in June 2000 and September 2001, and (E) 

 juvenile fish caught September 1999-2002. For clarity, 

 error bars for the average scale radius at each interval 

 are not shown. 



decrease in spacing of circuli at the scale margin in 

 September. 



Among maturing fish, average spacing of the last two 

 circulus pairs at the scale margin decreased greatly 

 between the spring through early summer period and 

 early fall (Fig. 7B). The decrease in circulus spacing at 

 the scale margin during the summer occurred for both 

 maturing fish of mixed stocks caught in research nets 

 (gray and white symbols) and for CWT fish of known 

 stocks caught in the ocean sport and troll fisheries 

 (black symbols). The decrease also was very consis- 

 tent among year classes; 11 of the 12 year-class groups 



(grouped by release period and pooled across hatcher- 

 ies) of Table 2 showed significant negative correlations 

 between spacing at the margin and date of capture 

 (P<0.05, r=-0.40 to -0.59). In September the aver- 

 age circulus spacing at the scale margin was about as 

 low as the average circulus spacing in the annual ring 

 (about 0.035 mm). 



The decrease in spacing of circuli at the scale margin 

 over the summer mirrors a similar decrease over the 

 summer in apparent growth rates in FL of maturing 

 fish caught in research nets (Fig. 7C). The apparent 

 growth rates of maturing coho salmon were usually 



