Friedland et al.: Post-smolt growth, maturation, and survival of two stocks of Atlantic salmon 



659 



Penobscot 

 Connecticut 



1977 



1980 



1983 

 Smolt year 



1986 



1989 



Figure 4 



Return rates for 2SW salmon to the Penobscot and Con- 

 necticut rivers (A). Normalized or Z-transformed re- 

 turn rates for 2SW salmon to the Penobscot and Con- 

 necticut rivers (B). 



the Penobscot and Connecticut stocks, whereas the 

 winter indices averaged less than 0.044 mm. The 

 spring and winter index means were nearly identi- 

 cal for the two stocks, whereas the summer index 

 mean was greater in the Penobscot. The mean num- 

 ber of circuli deposited in the post-smolt growth zone 

 averaged 25 for the Penobscot stock and 22 for the 

 Connecticut stock (Table 2). Post-smolt growth-zone 

 length indices ranged from 0.913 to 1.577 mm and 

 averaged 1.425 mm for the Penobscot stock and 1.204 

 for the Connecticut stock (Fig. 5E). Differences in 

 the annual seasonal spacing indices and circuli 

 counts were also reflected in the pattern of mean cir- 

 culi spacings for all years: the Penobscot stock had 

 wider circuli spacing in the summer zone and a 

 greater number of circuli deposited prior to the win- 

 ter zone (Fig. 3). 



Comparison of post-smolt growth 



The analyses of variance suggest that post-smolt 

 growth was greater in the Penobscot stock, especially 

 during the summer season. Spring growth indices 



1 2- 

 1.0- 



065 

 0.060 

 055- 



E 0.07 



E 



0.04 

 1.6 



1.2 



J x i~_l^-.— Penobscot j { 



Connecticut 



B 



/W ( ^ 



♦' 



L,i 



p*-' K->* 



i 



V 



77 



79 



81 



— i — 

 83 



-I 1 — 



85 87 



89 



Smolt year 



Figure 5 



Mean and 95% confidence interval of the following pa- 

 rameters by smolt year: (A) freshwater zone length; (B) 

 spring growth-zone circuli spacing; (C I summer growth- 

 zone circuli spacing; (D) winter growth-zone circuli 

 spacing; and (E) post-smolt growth-zone length. All 

 measurements are in mm. 



ranged from 0.053 to 0.065 mm for both Penobscot 

 and Connecticut origin fish ( Fig. 5B ). Significant dif- 

 ferences between Penobscot and Connecticut spring 

 growth-zone means were found for 10 of the 14 smolt 

 classes, and of those 10 years there were equal num- 

 bers of years with greater means for the Penobscot 

 and Connecticut stocks (Table 3). Summer growth 

 indices ranged from 0.057 to 0.069 mm for both 

 Penobscot and Connecticut origin fish (Fig. 5C). Sig- 

 nificant differences between Penobscot and Connecti- 

 cut summer-growth-zone means were found for 11 

 smolt classes, and of those 11 years, 9 were years in 

 which the Penobscot stock had the greater mean 

 (Table 3). Winter growth indices ranged from 0.039 

 to 0.051 mm for fish of both Penobscot and Connecti- 

 cut origin (Fig. 5D). Significant differences between 

 Penobscot and Connecticut winter growth-zone 

 means were found for only for 8 of the 14 smolt 

 classes, and of those 8 years, there were equal num- 

 bers of years with greater means for Penobscot and 

 Connecticut stocks (Table 3). 



