Something new is happening in the cold waters of northern and western Alaska. Unusual injuries such as bite marks and flipper amputations are showing up on seals in the Bering Strait, Chukchi Sea and Beaufort Sea regions.
Ice-associated seals and Steller sea lions in particular appear to be in contact with a predator not typically observed in these waters, according to a group of scientists, hunters and subsistence managers who are watching the trend.
Who do they think is the likely culprit? Sharks.
Several species are known to visit the western and northern coasts of Alaska, including the sleeper shark, dogfish shark, Greenland shark and salmon shark. A variety of northern shark species seem to be following the movements of prey species venturing farther north due to warmer ocean temperatures.
That’s according to a group of scientists and observers from Alaska Sea Grant, the North Slope Borough Department of Wildlife Management, Kawerak Inc. and Ocean Associates Inc. who have been recording injuries and attacks on pinnipeds through stranding data, aerial survey sightings, marine mammal hunter observations and bycatch.
“People are providing information on harvested seals with amputated flippers because they don’t normally see that. These are not the marks of a killer whale. Killer whales have pegged teeth—the injury pattern would be different and community members are noting these are novel injuries,” said Gay Sheffield, the Alaska Sea Grant Marine Advisory agent based in Nome.
Sheffield and others presented a scientific poster about shark–pinniped interactions at the Alaska Marine Science Symposium in Anchorage last January.
The poster, titled “Sharks and shark predation on ice seals and sea lions: Preliminary results from the Bering Strait and the North Slope regions, Alaska,” has a table that lists shark sightings, strandings and bycatch dating back to 1950. It shows increased reports from 2010 onward.
