August was the end of an unusual summer for Bristol Bay, which saw record temperatures, low water levels, and fires. Another phenomenon took place as well.
“All summer we’ve been noticing a lot of animal die-offs. A lot of birds, seals and whales,” said John Christensen, the tribal president of Port Heiden.
In August, he heard about an unusual stranding near the village – a salmon shark on the beach near second cape. So he went to see for himself.
“It was a probably five-foot-long shark that looked fairly fresh,” he said.
Christensen said this isn’t the first salmon shark to get stranded near the village. But it was the largest he’d ever seen. He left the carcass on the beach, where he said scavengers got to it, and reported the stranding to the local environmental observation network. That network, where local observers can track environmental occurrences, only lists two other recorded instances of sharks washing up on Alaskan shores.
Like many unsolved mysteries from this unusual summer, the reason for the stranding is unknown. Cindy Tribuzio, a research fish biologist in Juneau, at the Auke Bay Laboratories with the National Marine Fisheries Service, said there are a few types of sharks that aren’t strangers to Alaska’s waters – the salmon sharks are among them.
“They’re surface feeders, they feed at depth, they’re highly migratory. But they also stick around all year. So they do a little bit of everything,” she explained.
It’s not uncommon to find sleeper sharks on shore – usually after they get caught in commercial fishing nets. But salmon sharks, like the one in Port Heiden, don’t end up in this situation as often.
“They’re tough. And they do get wrapped up in gillnets and that has happened. And I’ve seen a few reports of gillnetters catching them in Bristol Bay this year,” she said, adding that salmon sharks are more likely to rip a hole in the net than get caught in it.
As far as the possible reason for the stranding, she doesn’t think it has anything to do with warmer waters. Salmon sharks are good at maintaining their body temperature and they can be found as far south as Hawai’i.
“The sharks at the higher latitudes are generally a little more tolerant to the temperature swings,” Tribuzio said. “But that has a lot more to do with the reproductive strategy. Most sharks are pretty generalist feeders, so food resources aren’t really a problem. And, you know, they’re such capable swimmers that they can move with the temperature as needed.”
Tribuzio says that off the west coast, smaller sharks have been stranded due to bacterial meningitis in their brains, which could be affected by warming water. But that’s probably not the case with this shark.
Still, it’s one more creature in a growing number of animals found dead across Bristol Bay. Along with significant seabird die-offs, near Port Heiden, there have been reports of small whales and porpoises, walrus and sea otters washed up on shore.
If you see a stranded marine animal, you can contact NOAA’s 24-hour statewide stranding hotline at 877-925-7773.
Contact the author at isabelle@kdlg.org or 907-842-2200.
