An unusually high number of orcas have died this year after getting caught in commercial fishing equipment off the Alaskan coast, according to the National Oceanic and Atmospheric Administration (NOAA). This uptick in deaths, per a trade association representing local fishers, may be connected to a “new behavior” from the animals.

Since the start of this year, nine orcas—also known as killer whales—have died in groundfish trawl fisheries in the Bering Sea near the Aleutian Islands. Another became entangled but was released alive, per NOAA, bringing the total number of “incidentally caught” orcas to ten so far in 2023.

For comparison, just five orcas in the Bering Sea died or became seriously injured after entanglement in fishing gear during the five-year period between 2016 and 2020, according to NOAA statistics.

The federal agency is now investigating the incidents to confirm the cause of death (because it’s possible some orcas were already dead before being caught) and to conduct genetic testing to determine which population they belong to, per the statement. As of now, experts do not believe the animals are part of the Southern Resident population, a critically endangered group off the coast of the Pacific Northwest, writes Insider’s Katie Hawkinson.

This year, some fishers have observed a novel behavior among orcas that might be related to the recent entanglements, according to a statement from Groundfish Forum, a trade association that represents 19 trawl vessels.

“In 2023, our captains have reported an increase in the number of killer whales present near our vessels, where they appear to be feeding in front of the nets while fishing,” per the statement. “This new behavior has not been previously documented and marine mammal scientists are not sure why this change has occurred.”

Orcas are clever, social animals that can learn new behaviors from each other. These crafty creatures have figured out how to exploit human fishing activities, such as by snacking on fish caught on longlines. Once one orca figures out an opportunistic feeding technique, scientists say, others can learn from watching and follow suit, per Live Science’s Sascha Pare.

That may be what’s happening this year near Alaska. To try to get to the bottom of the recent deaths, Groundfish Forum asked Hannah Myers, a marine biologist at the University of Alaska Fairbanks, to spend a week aboard a fishing vessel in May, reports the Anchorage Daily News’ Hal Bernton.

During that time, roughly two dozen orcas arrived when the vessel started fishing operations—and they stuck around.

“Certain pods were targeting the vessel, and I think it’s very lucrative behavior for them, because they are staying with the vessel 24/7,” Myers tells the Anchorage Daily News.

Using an underwater microphone, Myers recorded orcas making clicking sounds that scientists think may be connected to foraging behaviors. Based on the recordings, the mammals seemed to be following the net as the vessel towed it deep underwater; she also observed them at the surface as fishers pulled the nets up from the depths. These behaviors are “high-risk” for the orcas, she tells the publication.

Additionally, Myers noticed orcas hanging out near discharge chutes, where fishers send accidentally caught halibut—a prohibited species—back into the water.

Groundfish Forum, for its part, says it does not release halibut into the water when orcas are nearby. Its members are “committed to finding solutions to this unprecedented challenge,” per its statement. “Vessels are experimenting with gear modifications that may prevent whales from entering the net.”

Entanglement deaths concern scientists because orcas are slow to reproduce, meaning that even a few mortalities could affect population numbers more broadly in the future. However, orcas do appear to ramp up breeding efforts if several of their pod members die, per the Alaska Department of Fish and Game.

“Much remains to be learned about the reproductive behavior of killer whales,” the department writes.

An estimated 50,000 orcas live in oceans around the world, with roughly 2,500 of them living in the eastern North Pacific Ocean, per NOAA.

Under the Marine Mammal Protection Act, enacted in 1972, vessel owners or operators must report to NOAA all deaths or injuries of marine mammals, such as orcas, that take place during their operations.

In addition to the ten orca entanglements in the Bering Sea this year, NOAA is also reviewing a separate incident that occurred on June 7. On that day, an orca became entangled and died during Alaska Fisheries Science Center’s longline survey for sablefish and groundfish on the Central Bering Sea slope.