Are killer whales the culprit that's causing sea lion trouble in western Alaska?

October 15, 2009 

Alaska's fisheries are once again under the gun as the National Marine Fisheries Service (NMFS) looks at the effects of fishing on the endangered Steller sea lion (SSL). At stake are the multi-billion dollar groundfish fisheries of the Gulf of Alaska and Bering Sea. These fisheries are the economic engine that provides most of the jobs and revenue for coastal communities like Kodiak, Dutch Harbor, and the northern Bering Sea villages that participate in the Community Development Quota program. But new research may shed light on what is happening to Steller sea lions, and this could be good news for Alaska's fishery dependent communities.

According to recently published research out of the Alaska Sea Life Center in Seward, the endangered Steller sea lion may serve as a main course meal to some killer whales. This study seems to support the findings of the National Research Council (NRC) that killer whale predation may play a critical role in SSL recovery. Let's hope the National Marine Fisheries Service, charged with protecting sea lions and managing federal fisheries, takes this important new information into account as it completes it's assessment of current fisheries restrictions in Alaska. Called a Biological Opinion, this assessment is scheduled for release to the public in March and will impact communities throughout Alaska.

As part of a study to look at sea lion mortality, scientists at the Alaska Sea Life Center (ASLC) and Oregon State University (OSU) implanted sensors in 21 SSL in the Prince William Sound region. The transmitters were designed to release body cooling data upon death of the animal. Data recovered from four of five animals indicated rapid temperature drops likely caused by acute death at sea. The researchers concluded this was probably caused by killer whale predation. The study is scheduled for publication in the Endangered Species Journal. Co-author Markus Horning was recently quoted saying. "It could be coincidence or it could mean that predation is a much more important factor than has previously been acknowledged." In other words, killer whales may have been caught in the cookie jar.

The reason this issue is important to Alaskans is that the Endangered Species Act requires that protective action be taken even when the cause of a population decline is unknown. It's important that those protective actions are not misdirected. The endangered western stock of SSL, at more than 45,000 animals, is among the highest of all endangered species. The population has increased overall by about 14% since 2000 but recovery is uneven. Speculation remains about why this is the case, and why the population in the distant western Aleutian Islands may continue to decline. While the NRC and some marine mammal scientists believe that killer whale predation may be a factor affecting SSL trends, the National Marine Fisheries Service (NMFS) has favored a hypothesis that nutritional stress, potentially caused by competition for prey with fishermen, may be impacting sea lion reproductive rates. The Steller Sea Lion Recovery Team rated both hypotheses as potentially high threats to the recovery of Steller sea lions.

Congress allocated over $80 million in research money to help unravel the mystery of the SSL decline and impediments to its recovery. Since that time much work has been produced and, though the question has not yet been answered, this recent study suggests that factors like killer whale predation may be at work. The Endangered Species Act requires that all the scientific evidence be considered. Let's hope the National Marine Fisheries Services takes a hard look at all these factors, not just the potential impact that fishermen might have on sea lions, as they conduct their review. The economic health of our fishery dependent communities depends on it.

Frank Kelty is a 38 year resident and former mayor of the Aleutian Island community of Unalaska. He is currently the President of the Marine Conservation Alliance.

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