Gangs of killer whales have been stealing catch from Alaskan fishermen in the Bering Sea. The orcas are even attempting to drive the fishers out of their fishing areas, targeting and following specific boats for days.

After years of friendly coexistence with Alaskan fishermen, the killer whales are appearing in greater numbers and with more aggression, clearing entire lines of cod and halibut. Sometimes, the orcas even force the fishermen back to port.

“We’ve been chased out of the Bering Sea,” Paul Clampitt, Washington state-based co-owner of the fishing vessel “Augustine,” told the National Post.

Jay Hebert, who has been fishing in the Bering Sea for nearly 40 years, told the Alaska Dispatch News that the whales are completely undeterred by the sonar technology used to keep them away.

Herbert said the past five years have been particularly grueling. Fishermen in the Bering Sea can catch 20,000 to 30,000 pounds of fish individually per day, and some fishers have reported losing their entire daily catch to the whales.

“It’s gotten completely out of control,” Herbert said.

Robert Hanson, captain of the FV Oracle, told Alaska Dispatch News he thinks the mother orcas are teaching their young to target the halibut and cod the fishermen are attempting to catch.

Hanson was followed by a group of killer whales in April. He lost 12,000 pounds of halibut to the aggressive whales and 4,000 gallons of fuel trying to escape them.

Studies show nearly 1,500 whales live in the Western Alaskan waters today.

NOAA fisheries biologist John Moran told the Alaska Dispatch News that killer whales are skilled hunters. The orcas are able to learn the sounds of different boats and the hydraulic systems used to lower fishing gear into the water, letting them target specific boats.

“Grabbing a fish off a line is nothing,” he said.