Science Spotlight

Steller sea lions (Eumetopias jubatus) were listed as Threatened under the Endangered Species Act in 1990, following a documented >80% reduction in population size.  Based on genetic differences, Steller sea lions within U.S. waters have been segregated into two stocks: the Eastern and Western distinct population segments.  The geographical separation between these populations occurs at 144° West longitude or Cape Suckling, AK:

While the Eastern stock steadily increased in population size through the 1990s, the Western stock continued to decline and was subsequently reclassified as Endangered in 1997 [United States Federal Register 62:30772-30773].  In 2013, the Eastern stock of Steller sea lions was delisted (removed from the List of Endangered and Threatened Wildlife). 

Today, the Western stock appears to be stable or slightly increasing as a whole but strong regional differences have be reported across rookeries and haul-outs.  Despite greater than twenty years of research investigating the Western stock's population trends, the drivers behind the failure to return to historical population size estimates remains unclear. Hence, the Western stock of Steller sea lions remains listed as an Endangered Species. 


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