Beacham et aL: Population identification of Oncorhynchus tshawytscha by variation at microsatellite loci 



251 



particularly prior to June. For the fishery samples from 

 1997 to 1999 collected in April of each year, chinook salmon 

 from the Chilcotin River and Nicola River drainage were 

 important contributors to the fishery, as they, combined, 

 comprised approximately 50% of the samples from the 

 net fishery prior to 19 April (Appendix Table 1). By late 

 April, the Chilcotin River population constituted on aver- 

 age approximately 20% of the fishery samples, and the 

 Nicola drainage populations about 10%. The Birkenhead 

 River population was also identified as contributing S'/f to 

 10%^^ of the catch in the early lower river fishery but was 

 virtually absent from the fishery after 3 May. The Stuart 

 and Nechako river drainage populations were identifed as 

 contributing significantly to the early catches, with esti- 

 mates as high as 20% in some weeks in some years. Upper 

 Fraser River populations contributed more to the fishery in 

 May, and the significant populations were from the Holmes 

 River, the Fraser River mainstem at Tete Jaune, the Salmon 

 River, and the McGregor River (Appendix Table 1). 



On a regional basis, mid Fraser River populations were 

 the dominant group of chinook salmon in the catch in 

 April, and comprised at least 30% of the catch until late 

 May (Fig. 2). Upper Fraser River populations did not oc- 

 cur in any significant proportions in the fishery until the 

 last week of April. By late May, they were the dominant 

 contributors to the lower river fishery and by June could 

 comprise approximately 70%^^ of the weekly catch. South 

 Thompson River and North Thompson River populations 

 comprised only trace proportions of the fishery samples 

 from April through to the end of June. In fact, the con- 

 tributions of populations in the entire Thompson River 

 drainage were dominated by the tributary Nicola River 



Table 6 



Percentage composition of a sample of 83 coded-wire 

 tagged (CWT) Fraser River chinook salmon obtained from 

 fisheries in British Columbia in 1997 and estimated using 

 13 microsatellite loci with a 50-population Fraser River 

 baseline. Because all fish in the sample were marked with 

 CWTs, the actual composition of the sample is known. 

 Standard deviations are shown in parentheses. 



Population and 

 sum for region 



Dome Creek 



Sum for Upper Fraser region 



Nechako-Stuart 



Quesnel 



Sum for Mid Fraser region 



Chilliwack 



Harrison-Stave 

 Sum for Lower Fraser region 

 Sum for Birkenhead region 

 Sum for North Thompson region 



Lower Shuswap-Upper Adams 



Middle Shuswap 



Sum for South Thompson region 

 Sum for Lower Thompson region 



drainage populations, and these populations were pres- 

 ent from the beginning of sampling in early April to the 

 end of sampling in late June. Lower Fraser River popula- 



