Steller sea lions most likely victims of human-caused marine mammal deaths in Alaska

a sea lion on rocks
A Steller sea lion, viewed in 2009 by the crew of the NOAA ship Fairweather, rests on a rock on an Alaska shore. Steller sea lions were the marine mammals most likely to be killed by entanglements in fishing gear or marine debris, according to NOAA’s latest five-year report. Steller sea lions in the western part of Alaska are listed as endangered, while the population in eastern Alaska was previously protected as threatened but became healthy enough to be delisted in 2013. (NOAA)

Over a five-year period, 867 Alaska sea lions, seals, whales and small cetaceans like dolphins died or were gravely injured from interactions with humans, according to a report newly released by the National Oceanic and Atmospheric Administration.

The report, required by the Marine Mammal Protection Act, lists documented cases of human-inflicted harm from 2016 to 2020 to mammal species managed by NOAA’s National Marine Fisheries Service.

The vast majority of cases involve entanglements in fishing gear or marine debris, and Steller sea lions made up the vast majority of the animals that fell victim, said the report, which was released by the NMFS Alaska Fisheries Science Center.

Steller sea lions have been protected since 1990 under the Endangered Species Act. The Western segment of the population, which ranges from the Prince William Sound area to the Aleutian Islands, has declined precipitously and is listed as endangered. The Eastern segment of the population is now considered recovered and healthy; it had been listed as threatened but was delisted in 2013.

The bulk of the mortality and serious injury cases in the report involved Steller sea lions from the plentiful Eastern population segment. Among those animals, entanglements in fishing gear were the leading causes of death, followed by hookings in salmon-fishing gear. Sea lions can be attracted to lures intended for salmon, the report noted. “Steller sea lions that have ingested gear are found with flashers hanging from the edge of their mouth connected to monofilament line that is attached to a swallowed hook,” it said.

While the fishing-related deaths of Eastern population segment sea lions generally involved the salmon harvests, the 146 documented deaths of or grave injuries to Steller sea lions in the Western population segment generally involved the groundfish trawl harvests, the report said.

Seal deaths listed in the report were also dominated by entanglements, in many cases with fishing gear or debris encircling the animals’ necks. For large whales, for which there were over 50 deaths or grave injuries during the five-year period, the largest number of cases involved entanglement in gear, followed by ship strikes.

The numbers and patterns in the current report are similar to those documented in NMFS’ previous five-year report, which listed 922 human-caused deaths or serious injuries to marine mammals from 2013 to 2017.

Cases in the report do not include traditional Indigenous subsistence harvests, which are allowed under the Marine Mammal Protection Act. The report does not include Alaska marine mammals that are managed by the U.S. Fish and Wildlife Service – walruses, polar bears and sea otters.

Alaska Beacon is part of States Newsroom, a network of news bureaus supported by grants and a coalition of donors as a 501c(3) public charity. Alaska Beacon maintains editorial independence. Contact Editor Andrew Kitchenman for questions: info@alaskabeacon.com. Follow Alaska Beacon on Facebook and Twitter.

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