362 



Fishery Bulletin 103(2) 



Odd year smolts 



Even year smolts 



~i i i i i i i i i i r 



7 10131619 22 3 6 9 121518 1 4 



Circuli pair 



Figure 5 



Seasonal scale growth of Kvichak and Egegik ocean age- 

 2 sockeye salmon (O. nerka) that entered the ocean as 



smolts during odd- ( ) and even- ( ) numbered 



years, 1952-2000. Growth of salmon spending one (age 

 1.2) and two years (age 2.2) in freshwater are shown 

 separately. Circuli pair ordering restarts at the begin- 

 ning of each new growing season (SW1, SW2, SWPLl. 

 95% CIs are shown at each measurement. Age 1.2 = 1 

 year in freshwater and 2 years in saltwater. 



1 4 7 10 13 16 19 22 3 6 9 12 15 18 1 4 



Circuli pair 



Figure 6 



Percent change in scale growth between ocean age-2 

 sockeye salmon (O. nerka) entering the ocean during 

 even years and those entering during odd-numbered 

 years. Growth patterns represent ocean rearing periods 



prior to 1977 ( ) and after 1976 ( ). Even-year 



smolts encountered odd-year pink salmon (O. gorbuscha I 

 during the second year at sea (SW2). 



growth during SW2 diverged two or three circuli af- 

 ter the peak (Fig. 2). Late season growth of even-year 

 smolts during SW3 was greater than late season growth 

 during SW1 and SW2, whereas growth of odd-year 

 smolts during SW3 was intermediate to SW1 and SW2 

 growth. These relatively large, older fish experienced a 

 longer growing season, especially during even-numbered 

 years, when few pink salmon were present. 



Growth during homeward migration (SWPL) of ocean 

 age-3 sockeye salmon 



The peak return of sockeye salmon to Bristol Bay occurs 

 near 3 July. Scale growth during the homeward migra- 

 tion peaked at circuli 3 and 4, then declined (Fig. 2). 

 Peak growth was less than that of SW1, but greater 

 than SW2 and SW3 growth. No growth difference was 

 detected between odd- and even-year migrants during 



the period of homeward migration. Spring growth after 

 1976 was 5-10% greater than that during the earlier 

 time period (Fig. 4). 



First year ocean (SW1) growth of ocean 

 age-2 sockeye salmon 



Scale growth patterns of ocean age-2 Kvichak and 

 Egegik sockeye salmon were remarkably similar to that 

 of ocean age-3 sockeye, especially among those having 

 the same freshwater age (Fig. 5 1. Sockeye salmon that 

 had spent two winters in freshwater had significantly 

 greater SW1 peak growth compared with those spending 

 one winter in freshwater (Kvichak stock: df=85, ^=6.772, 

 P<0.001). Growth of age-2. smolts during the first eight 

 circuli averaged 9% higher compared to age-1. smolts. 

 However, as with ocean age-3 salmon, postpeak growth 

 of age-2 smolts averaged 3.5% less than that of age-1. 



