Pacific Harbor Seal (Phoca vitulina richardii, Gray 1864)

Abstract

The Pacific harbor seal, Phoca vitulina richardii (sometimes referred to as P. v. richardsi), occurs along the coast and islands from Japan to Alaska; the west coast of Canada and USA; and to the west-central coast of the Baja California Peninsula, Mexico. There are approximately 348,961 individuals, including 11,967 (95% Credibility Interval: 9,619–16,284) individuals in Mexico. The harbor seal’s diet in Mexico has been documented using fecal analysis of prey hard parts and metagenomic studies and from stable isotope studies which identified habitat use. Genetic studies of seals from five colonies in Mexico indicated that haplotype diversity was two times lower and nucleotide diversity was four to nine times lower than in the rest of the Pacific. A latitudinal cline has been described for the timing of both pupping and molting. There is a delay in the mean pupping date from the southernmost colony, San Roque Island (27 January), to the northern colony on Todos Santos Island (16 February). Molting starts on San Roque on 27 February, while on Todos Santos, it occurs on 18 April. At one coastal colony (Punta Banda Estuary, Baja California), recreational activities affected important events such as nursing and molting. This colony was monitored for six pupping seasons, which showed that pup production was reduced with unfavorable oceanographic conditions, i.e., warm sea surface temperature and low chlorophyll concentration, proxies for food availability. Fishermen at four colonies west of the Baja California Peninsula considered that the harbor seal interferes little with their livelihood. The International Union for the Conservation of Nature (IUCN) Red List has harbor seals listed as Least Concern worldwide and occupy the lowest category (Under Special Protection) in the Mexican List of Species at Risk. New data collected on harbor seals in Mexico indicate that the Mexican listing may be changed to Threatened in the future.