Pods of killer whales are reportedly stalking Alaskan fishermen and driving them out of fishing areas while robbing them of their catch.

The National Post reports that black cod and halibut fishers are being surrounded by orcas acting like “motorcycle gangs” and “chased out” of their areas of operation in the north Pacific.

Paul Clampitt, who co-owns the fishing vessel Augustine, told the publication: “We’ve been chased out of the Bering Sea.”

He said he installed electronic noisemakers on the vessel in an attempt to ward off the pods of orcas, but claimed the mammals adjusted to the deterrent to the point where “it became a dinner bell”.

John McHenry, who owns fishing vessel Seymour, told National Post the orcas are acting like a “motorcycle gang”.

“You’d see two of them show up, and that’s the end of the trip. Pretty soon all 40 of them would be around you.”

The killer whales’ tactics are causing significant damage to the fishermen’s businesses, Alaska Dispatch News reported.

Speaking to the news outlet, Bering Sea longliner Jay Hebert said that on a normal day, fishermen can collect between 20,000 and 30,000 pounds of halibut, but if a pod of killer whales sees their boat the mammals will strip its fishing lines of any catch, sometimes leaving just the “lips” of halibut stuck to the hooks.

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Mr Hebert said the killer whales have become increasingly aggressive over the years and the situation has now got “completely out of control”.

One fishing boat captain described how he had been “harassed non-stop” on a fishing trip in April, when pods of orcas cost his crew 12,000 pounds of halibut and 4,000 gallons of fuel in an attempt to outrun the mammals.