Genetic variability and population decline in Steller sea lions from the Gulf of Alaska

The western stock of the Steller sea lion (Eumetopias jubatus) was listed as endangered in 1997 due to its decline in numbers since the 1960s. We examined haplotypic diversity using nucleotide-sequence analysis of the control region of the mitochondrial DNA (mtDNA) from animals collected in 1976-1978 from the western and central Gulf of Alaska and compared results to previously published data from animals collected in the 1990s from the same geographic areas. No significant differences were found in frequencies of haplotypes between the two time periods, and genotypic diversity was high for all populations and time periods studied. It is concluded that, despite reduction in numbers, populations in the Gulf of Alaska have not lost appreciable genetic diversity, and if populations are allowed to recover, no long-term change in fitness is expected.