Genetic variability in four hatchery strains of coho salmon, Oncorhynchus kisutch (Walbaum), in Chile

Coho salmon, Oncorhynchus kisutch (Walbaum), is intensively cultured in Chi le. An increasing proportion of the eggs necessary to sustain the culture a re locally produced by some hatcheries. However, there is no information ab out the origin or the genetic variability in these strains. The present stu dy analysed allozymic variability and its distribution within and between s ome commercial strains of coho salmon in southern Chile. The genetic variab ility was estimated using horizontal starch gel electrophoresis, Samples of coho salmon were obtained randomly from four Chilean hatcheries. Twenty-fi ve enzymatic systems were examined, representing 51 enzymatic loci, Eight l oci showed variability in at least one strain, which represented a total po lymorphism (P) of 15.7%. Only the PGM-1* locus was variable in all strains. The remaining loci were fixed in at least one strain. Total heterozygosity (HT) and within population heterozygosity (Hs) were 0.35% and 0.36% respec tively. The index of genetic diversity (GST) was 1.5%. The results confirm previous reports of low genetic variability in cultured strains of coho sal mon in Chile, below that observed in their native range, which suggests los s of the genetic variability caused by genetic drift or other causes in the se strains.