Sperm whales — the world’s largest toothed predators, which can grow up to 67 feet long and weigh over 125,500 pounds — have been targeting black cod fishermen’s boats in the Gulf of Alaska, pilfering their catches in a sort of amazing marine heist.
Alaskan fishing crews first reported that sperm whales had been robbing them in the 1970s, but it was in 2009 — more than 30 years later — when a group of scientists caught them on video for the first time. In the footage, a sperm whale uses its long jaw to create tension on the line, which snaps fish off the hooks, as though they were shaking apples from a tree. This behavior is called depredation.
“I don’t know how to quantify their intelligence but their effectiveness is almost perfect,” 20-year veteran boat skipper Stephen Rhoads told the BBC. “That they’re getting better at this every single year and it’s less work for them to hang out with us and take our fish than it is to dive down and get them off the bottom. There’s no doubt that these creatures are very smart.”
Since the thieves first began taking the fishers’ catches in the ’70s, two factors have exacerbated the problem. First, the fishing season has been extended from just a two-week period to an eight-month long season; second, commercial whaling has been banned. Not only are more whales able to steal now, but they get more time to perfect their technique.
“Plan on travelling to Alaska this summer to experience some of the “Last Frontier” yourself,” says Bob Standish, Owner, Bob’s Cabin. “Enjoy a great fishing experience and spectacular unsurpassed scenery while staying at a fishing lodge on the Kenai Peninsula. We are located on the world famous Kenai River and offer guided sport fishing throughout the entire Kenai Peninsula in both fresh water rivers and the saltwater environment. Fish for tackle busting red, king and silver salmon in the freshwater rivers. You can catch gigantic Pacific Halibut up to 200 pounds or more in the Gulf of Alaska salt waters.”
In 2003, the Southeast Alaska Sperm Whale Avoidance Project (SEASWAP) was launched to better understand sperm whales and to figure out ways to stop them from pilfering fishing crews’ catches. Since the project’s launch, scientists have discovered several new findings about the Gulf of Alaska sperm whale population.
In SEASWAP’s study area, scientists have observed 10 whales around fishing boats, which is unusual — adult males typically hunt alone. This behavior indicates that depredation is a socially transmitted behavior between whales.
Scientists have also found that whales, which use echolocation to hunt, find fishing boats thanks to the sound of the vessels’ engines shifting gears as they haul in catches.
“They’re premeditated,” Rhoads told the BBC. “But they are using clues of how we’re fishing to know that there’s definitely gear on the bottom, that we have fish on hooks a half mile under the surface and the whales have figured out the sounds of our boats in action meaning that the fish are coming up.”
Of solutions to depredation that the SEASWAP team has tried, monitoring appears to be the most effective. Researchers tag whales with satellite trackers, allowing them to monitor and track the massive mammals. Fishing crews can check online or contact SEASWAP to find out if the whales are close to their area, and can choose to move to another place in an attempt to avoid having their catches stolen.
“I don’t know if there’s one answer to the depredation issue,” SEASWAP’s Lauren Wild told BBC. “But I think being informed and aware of how these animals are behaving are all important to really get a grasp on what they’re doing and how they’re doing it in order to prevent it.”