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Fishery Bulletin 94(3), 1996 



Figure 2 



Map of the South Island of New Zealand showing the locations of populations 

 of chinook salmon used in the genetic analysis. 



There is a substantial database for pro- 

 tein-coding loci on North American chinook 

 salmon (e.g. Utter et al., 1989, 1992; 

 Bartley and Gall, 1990; Bartley et al., 

 1992), including the Battle Creek popula- 

 tion, and a growing database of mtDNA 

 variation (Nielsen et al., 1994, a and b). 

 These two types of data can be more pow- 

 erful than either alone for studying rela- 

 tively recent colonization events (Wade et 

 al., 1994). The purposes of the present in- 

 vestigation were to use variation at pro- 

 tein-coding loci and mtDNA to investigate 

 1) the nature of the founding population 

 (e.g. fall, winter, or springl, 2) whether NZ 

 fish differ in gene frequencies from the 

 descendants of the source population, 3) 

 whether NZ populations differ from each 

 other, and 4) whether NZ fish differ in the 

 levels of genetic variation from descen- 

 dants of the source population. 



Materials and methods 



History and origins of NZ chinook 

 salmon 



history traits (Quinn and Bloomberg, 1992; Quinn 

 and Unwin, 1993 ), raising the possibility that geneti- 

 cally distinct populations have evolved within about 

 20-25 generations and presenting the opportunity for 

 an in-depth study of salmon population differentiation. 

 Genetic differentiation among populations may 

 arise through selection regimes operating on heri- 

 table traits and through genetic drift at the time of 

 colonization (founder effects) and after colonization. 

 Examination of traits not subject to strong selection 

 can provide insights into the importance of genetic 

 drift. Allelic variation at protein-coding loci detected 

 by protein electrophoresis, and more recently, direct 

 examinations of mitochondrial ( mt) and nuclear DNA 

 have provided valuable sources of largely neutral 

 molecular genetic markers that permit estimates of 

 degrees of divergence among populations (e.g. Utter, 

 1991; Carvalho and Pitcher, 1994). Such techniques 

 have helped identify source populations (Hendry et 

 al., in press) and have shown differences between 

 transplanted populations and their source popula- 

 tion (GharrettandThomason, 1987; Ward etal., 1994) 

 or differences among populations founded by coloniza- 

 tion in the new habitat ( Krueger and May, 1987 ). How- 

 ever, population divergence after transplantation is not 

 always detected (Snowdon and Adam, 1992). 



The first shipment of fertilized chinook 

 eggs to NZ was collected from spring-run adults cap- 

 tured in the McCloud River, a tributary of the upper 

 Sacramento River (Fig. 1), 2-27 Sept. 1875 (United 

 States Commission of Fish and Fisheries, 1874- 

 1901). Subsequent shipments of 100,000-500,000 

 chinook embryos from Baird Station on the McCloud 

 River to the South Island continued to the end of the 

 century, but no self-sustaining populations were es- 

 tablished and records of even isolated individual 

 salmon are subject to doubt (McDowall, 1994). There 

 were apparently five shipments from California in 

 the 1900's, arriving in NZ in January-February 1901 

 (500,000 embryos), 1904 (300,000), 1905 (300,000), 

 1906 (500,000), and 1907 (500,000; McDowall, 1994). 

 McDowall ( 1994) concluded that the shipment which 

 arrived in 1904 produced the first returns to the 

 Hakataramea Hatchery in 1907 and that this and 

 the subsequent shipments founded the NZ runs. 

 These embryos were shipped from Battle Creek, but 

 it is unclear whether they originated from Mill Creek 

 or Battle Creek. 



Collection of samples 



Juvenile salmon (100 per population) were collected 

 from the Waimakariri, Rakaia, and Waitaki rivers 



