18 



Fishery Bulletin 98(1) 



Variation among stocks 



The three sockeye salmon stocks in Barkley Sound 

 were genetically distinct at all six loci examined. All 

 pairwise tests of allele frequencies among stocks were 

 highly significant at all loci iP<0.001). At Omy77, the 

 frequency of the Omy??^"* allele ranged from 0.005 in 

 Henderson Lake sockeye salmon to 0.449 in Sproat 

 Lake fish, and the frequency of Omy77^'^'' ranged from 

 0.216 in Sproat Lake fish to 0.546 in Henderson Lake 

 fish (Table 3). Substantial differentiation in allelic 

 frequencies among stocks was observed at Ots3. For 

 example, the frequency of OtsS'^'^ in Henderson Lake 

 sockeye salmon was 0.114, whereas in Sproat Lake 

 fish it was 0.543. Similarly, the frequency of Ots3^^ 

 was 0.059 in Sproat Lake fish and 0.243 in Hender- 

 son Lake fish. At OtslOO, the frequency of OtslOOi^s 

 ranged from 0.256 in Sproat Lake sockeye salmon to 

 0.504 in Henderson Lake fish (Table 3). Although the 

 three stocks were distinct at OtslOS, the allele fre- 

 quency variation was less marked at that locus. At 

 OtslOT, the combined frequency of four alleles (81, 

 109, 113, 117) was greater than 0.95 in all stocks, but 

 stock differentiation was nonetheless apparent. For 



example, the frequency of Otsl07'^' was 0.135 in Great 

 Central Lake sockeye salmon, but < 0.010 in the other 

 two stocks (Table 3). Variation in allelic frequencies at 

 OtslOS was evident among stocks, with the frequency 

 of OtslOS^" ranging from 0.000 to 0.196. Strong 

 genetic differentiation among these three stocks was 

 evident at all six microsatellite loci. 



Comparison of the relative magnitude of differen- 

 tiation among stocks and among samples from the 

 same stock collected in different years showed that 

 differentiation among stocks always exceeded tempo- 

 ral variation within stocks and was on average 12 

 times greater (Fig. 2; Table 4). At Ots3, the differ- 

 ences among stocks were 235 times greater than the 

 observed annual variability. With data combined over 

 years, individual locus Fg-p estimates ranged from 

 0.013 to 0. 107, with an overall value of 0.056 (Table 4). 

 The loci displaying the greatest differentiation among 

 stocks were Ots3 and Omy77, whereas Otsl03 dis- 

 played the least differentiation. Sproat Lake and Great 

 Central Lake stocks, both in the same river drainage, 

 were genetically the most similar (pairwise F^^ esti- 

 mate over all loci: 0.032). The Great Central Lake and 

 Henderson Laike stocks were more genetically distinct 



