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Microsatellite diversity in rainbow trout (Oncorhynchus mykiss) inroduced to Western Australia

Ward, R.D., Jorstad, K.E., Maguire, G.B.
Aquaculture 2003 v.219 no.1-4 pp. 169-179
Oncorhynchus mykiss, introduced species, microsatellite repeats, loci, genetic polymorphism, fish hatcheries, alleles, heterozygosity, genetic drift, Western Australia
Rainbow trout (Oncorhynchus mykiss) is endemic to the Pacific coast of North America and westward to the Kamchatka peninsula and Okhutsk Basin of Russia. Australian populations are derived from imports from New Zealand, the latter largely derived from Californian imports in 1883. We examined variation in 10 microsatellite loci in four populations of rainbow trout from Western Australia (WA). Three populations were from Pemberton hatchery stocks, and one was from a self-sustaining introduced wild population. All loci were polymorphic in all populations. There was substantial genetic differentiation among populations, with an average FST value of 0.19. The four populations averaged 3.80-4.10 alleles per locus, with average heterozygosities of around 0.47-0.58. Two hatchery populations, independent of each other since 1971, were no less variable than the self-sustaining population that has been independent of these hatchery populations since 1961. These populations were substantially less variable than North American populations. For six loci studied in common in Western Australia and North America, average heterozygosities were 0.56 and 0.75, and average numbers of alleles per locus were 3.8 and 10.5, respectively, despite larger sample sizes in the former. This loss of variation is attributable to about 100 years of isolation and genetic drift.