Genetic variation of microsatellite and mitochondrial DNA markers in broad whitefish (Coregonus nasus) in the Colville and Sagavanirktok rivers in northern Alaska

There has been concern that a causeway leading to oil production facilities in the Alaskan Beaufort Sea could affect the extent of emigration from, and immigration into, a population of broad whitefish (Coregonus nasus) in the Sagavanirktok River. To assess this, we analyzed the genetic relationships of the broad whitefish populations in the Sagavanirktok River, and the nearest adjacent population, in the Colville River. Three microsatellite loci from the nuclear genome, and the NADH-I gene of mitochondrial DNA (mtDNA), were analyzed. Diploid genotypes were determined with PCR amplification of the microsatellite loci, and mtDNA genotypes were identified with PCR amplification followed by sequencing of 798 nucleotides. Several alleles were identified at each locus and both populations had high levels of genetic variation. There is significant differentiation of the Sagavanirktok River and Colville River broad whitefish stocks for the three microsatellite loci (F-ST = 0.031) but not mtDNA (F-ST < 0.001). Possible explanations for the lower level of differentiation of mtDNA than microsatellites include female-mediated gene flow between populations, skewed sex ratios, natural selection, or mutation. The results indicate that there is limited gene flow between the Colville and Sagavanirktok rivers, which represent semi-isolated spawning populations.