Electrophoretic Variability in Dall's Porpoise (Phocoenoides dalli) in the North Pacific Ocean and Bering Sea

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Abstract
We describe electrophoretic variability at 26 loci in 360 specimens of Dall's porpoise (Phocoenoides dalli, Cetacea, Phocoenidae) collected from three locations in the Bering Sea and North Pacific Ocean. Nine of the 11 variable loci were polymorphic at the P = 0.99 level. Average heterozygosity for these specimens was 0.058, an above average value for a mammal. This may reflect a large, stable population size. Although genotypic proportions from each location generally agreed with Hardy-Weinberg expectations, significant heterozygote deficiencies were detected at two loci in a sample from the North Pacific Ocean. The result of subdividing this sample and rechecking the Hardy-Weinberg proportions suggested that a region of mixing is present at 50°N to 52°N. A pooled sample of Bering Sea and North Pacific Ocean specimens resulted in larger chi-square values—one-third of the loci were statistically significant—than with the individual treatments of the two samples. We, therefore, rejected the hypothesis that the two samples represent one interbreeding population.