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

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.