HJORTand SCHRECK: PHENOTYPIC DIFFERENCES AMONG COHO SALMON 



TABLE 1.— Means, standard errors (in parentheses), and ranges for the morphological characters of the 1976 

 brood year hatchery samples of juvenile coho salmon and the hatchery water incubation temperatures for the 

 first month of incubation. Sample sizes were 15. The data are listed in north to south order of the sampling 

 locations. 



(Table 4), the agreement between brood years 

 was not particularly high, especially for scale 

 rows and branchiostegal ray counts. 



Although meristic counts and water temper- 

 atures during the incubation period of the eggs 

 are usually correlated (Barlow 1961), we found 

 that lateral series scale counts provided the only 

 meristic character significantly (a = 0.05) cor- 

 related with the temperature of the hatchery 

 water during incubation. Under the extant en- 

 vironmental conditions, incubation tempera- 

 tures may have little effect in determining the 

 morphological characters of our stocks. 



Among all possible statistically significant 



correlations between morphological characters 

 and the stream characteristics in Table 5, only 

 vertebral number and estuary length, and verte- 

 bral number and spawning distance, had corre- 

 lation coefficients >r = 0.50 (Table 6). All 

 other correlations each accounted for <25% of 

 the variation observed. Possibly we overlooked 

 some important environmental gradients, or 

 possibly the selective forces occur during peri- 

 odic environmental extremes or pulses that were 

 not accounted for in our environmental data. 

 Each of the counts significantly correlated with 

 at least two of the characters of the stream sys- 

 tems, suggesting that, if these characters are the 



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