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



47 



LOCR Oregon 4/24 - 5/20 release 



LOCR Oregon 5/21 • 6/14 release 



LOCR Wash. 4/24 - 5/20 release 



LOCR Wash. 5/21 -6/14 release 



NOOR 3/01 - 3/31 release 



NOOR 4/10- 5/10 release 



Ape 30 May 20 Jun 9 Jun 29 Jul 19 Aug 8 Aug 28 Sep 17 Oct 7 Oct 27 Nov 16 



B 



T3 



E 

 E 



1 * v 



* S . 2 9 '  ' 



r * - 



-  '  to 



T n a □ 



□ 



O  D 



Apr 30 May 20 Jun 9 Jun 29 Jul 19 Aug 8 Aug 28 Sep 17 Oct 7 Oct 27 Nov 16 



Date 



Figure 8 



(A) Grand-mean FLs (±2 SE) by 10-day intervals over the years 

 1975-2002 of CWT lower Columbia River (LOCR) Oregon and 

 Washington stocks and northern coastal Oregon stocks (NOOR) 

 of maturing coho salmon (O. kisutch). Only intervals with five 

 or more years of data are shown. (B) The corresponding aver- 

 age apparent growth rates between each 10-day interval. Note 

 the apparent decrease in growth rate between early and late 

 summer. 



rate. However, the large seasonal changes in growth rate 

 of coho salmon in the ocean are readily detectable from 

 the changes in circulus spacing on the scale. 



In June 2001, 2002, and 2003 average spacing of the 

 last two circulus pairs at the scale margin was positive- 

 ly correlated (P<0.01) with plasma IGF-I (insulin-like 

 growth factor-I) concentrations from juvenile fish caught 

 in the ocean in research nets (n=119, 163, and 206 and 



r=0.52, 0.52, and 0.59 in 2001, 2002, and 2003, respec- 

 tively) (Beckman 2 and Fisher, unpubl. data). Because 

 plasma IGF-I levels have been shown to be positively 



2 Beckman, B. 2004. Unpubl. data. Integrative Fish Biol- 

 ogy Program, Northwest Fisheries Science Center, National 

 Marine Fisheries Service, 2725 Montlake Boulevard East, 

 Seattle, Washington 98112. 



