A federal fishery agency reported last week that 10 killer whales were caught in the gear of trawl net vessels fishing this year in the Bering Sea and North Pacific waters off the Aleutian Islands.
Only one was released alive, according to a brief Alaska NOAA Fisheries statement posted online. A team is analyzing data collected about the other nine whales to determine the cause of injury or death, and also to determine which stocks these whales belonged to through reviewing genetic information.
Killer whales, also known as orcas, have been entangled in trawl gear off Alaska in years past, but the numbers reported in 2023 are higher. .
“The agency is working quickly to evaluate these incidents and will share findings as soon as possible, after all required analyses are completed,” the statement said.
The agency reported that another killer whale was entangled with longline gear set out by a vessel that a private vessel contracted to conduct a federal fishery survey in the Central Bering Sea. On June 7, a dead whale was observed caught up in gear, the statement said. NOAA Fisheries scientists were on board the survey vessel, which was designed to provide an assessment of black cod — also known as sablefish — populations, and that incident is also under review.
Bering Sea killer whales fall under the Marine Mammal Protection Act, which includes requirements for vessel owners or operators to report injuries or deaths.
All of the trawl vessels involved in the whale deaths this year were required to carry two federally contracted observers that collect information about the catch. Their observations about the killer whale have been submitted to the NOAA Fisheries team reviewing the incidents.
The whale encounters with trawl gear have been discussed on social media. Alaska NOAA Fisheries posted a statement Thursday headlined “Response to Recent Reports of Killer Whale Incidental Catches in Alaska.” The statement did not provide additional details about the incidents, including what types of trawlers encountered the whales, and an agency spokesperson didn’t respond to requests Friday afternoon for more information.
In a written statement, the Groundfish Forum, a Seattle-based trawl fishery group, confirmed that member vessels were involved in at least some of the whale deaths as well as the one released alive.
Groundfish Forum members operate 19 vessels that net and process yellowfin sole, Pacific Ocean perch and other bottom-dwelling species.
“Our fleet is committed to finding solutions to this unprecedented challenge. We have invested in research activities to better understand the change in killer whale behavior and how to avoid them,” the statement said. “Vessels are experimenting with gear modifications that may prevent whales from entering the net.”
For decades, killer whales have been drawn to fishing boats off Alaska. Longliners, which drop lines of baited hooks, have generated many of these encounter reports. The whales eat black cod, stripping them off hooks, as they’re brought to the surface.
Sablefish longliners have tried many tactics to fend them off, including blasting heavy metal music from the decks. Some have switched to fishing with baited pots to keep them away.
Trawlers also have had encounters with killer whales, including two — a male and female that died in 2020 died after being caught in Bering Sea flatfish trawl gear, according to a NOAA Fisheries document.
From 2014 to 2020, seven killer whales died or suffered serious injury due to encounters with all types of fishing gear, according to a federal study cited by the Groundfish Forum in the statement.
In recent years, Groundfish Forum trawler crews have encountered killer whales more frequently, and those contacts appear to have intensified this year.
“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,” said the statement from the Groundfish Forum, which called this “new behavior.”
Megan Williams, a fishery scientist with the Ocean Conservancy, said killer whales are incredibly intelligent animals, and that “conflicts arising with trawl fisheries need to be addressed,” along with larger concerns about how to manage the Bering Sea more holistically.
“This may represent a conservation concern for killer whales,” said Williams, who studied killer whale interactions with Bering Sea fisheries for years and noted that there are three broad ecotypes — fish-eaters, those that focus on marine mammal prey and a third group of which less is known.
In the North Pacific, adult killer whales are long-lived and reproduce slowly. The males can reach an age of at least 50 years and the females as old as 80, according to an Alaska Department of Fish and Game species profile posted online.
The fish-eaters feed on a wide variety of species, and large groups are often involved in hunting their prey. Typical dives last three to five minutes, but a lot is unknown about their diving behavior, according to the Department of Fish and Game document.
The NOAA and Groundfish Forum statements do not offer information on how the whales got caught in the nets. So, it is unclear whether they may have been low in the water column, or got entangled as the net was drawn to the surface.
Groundfish Forum trawler operators are still trying to understand why they are encountering more killer whales.
For the GroundFish Forum fleet, one area of concern has been halibut that they incidentally bring up as bycatch as they target other species.
Longline fishermen report that whales have taken halibut from hooks.
The trawl-caught halibut appear to be an attractant to the killer whales because they are designated as a prohibited species and must be discarded after they are brought on board.
To try to improve halibut survival rates, crews sort some halibut on deck and toss them back to the sea. The Groundfish Forum statement said that is not done when killer whales are present. Instead, they are sorted out below deck, and discarded through chutes.
“Killer whales were observed feeding on discarded halibut by Hannah Myers, a University of Alaska Fairbanks marine biology graduate student and researcher with the non-profit North Gulf Oceanic Society, which was contracted by the Alaska Seafood Cooperative to study killer whale behavior. Myers spent a week on a trawler in May to learn more about their interactions with the vessel and its gear.
“Basically every halibut I saw go out of the whole fish discharge chute — the whales were on it,” said Myers, who is finishing her doctorate degree and has focused her research on killer whales.
Myers said that she was far less concerned about the risk to the whales from feeding near boats than other behavior.
During her week aboard the vessel, Myers was able to track some 30 tows with a hydrophone that acts like an underwater recording microphone and was attached to a headrope of a net. Those recordings indicated that the whales were deep underwater as the net was being towed, and making clicking sounds associated with foraging. She said one possibility was that the whales were pursuing fish in front of the net, or possibly eating fish from the outer mesh or even chasing fish into the net.
“This is something that would be high-risk behavior for them,” Myers said.
Whales also were spotted around the nets as they came to the surface and brought to the boat, according to Myers, who said that activity also posed risks.
Since 2020, Myers said, killer whale deaths from the trawl fleet have been on the rise, though lower than in 2023. This year, she said, the majority of the dead whales were found inside the nets.
It is unclear why some killer whales have been focusing on the trawl nets. Myers said it could be due to a loss of other sources of prey that prompted a shift to more reliance on foraging around the trawlers.
During her week at sea, Myers estimated about two dozen whales were around the boat. They showed up when the boat started fishing and never left.
“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.
Correction: An earlier version of this story incorrectly reported the organization that paid for killer whale research on a catcher-processor vessel earlier this year by University of Alaska Fairbanks student Hannah Myers. She worked with the non-profit North Gulf Oceanic Society, which was contracted by Alaska Seafood Cooperative, an industry group.
Journalist Hal Bernton has covered Alaska fisheries issues extensively. He was a longtime reporter for The Seattle Times, and previously reported for the Anchorage Daily News and The Oregonian. Reach him at firstname.lastname@example.org.