SITKA, ALASKA Sperm whales, it seems, have gotten into the habit of picking fish off commercial longlining gear. It’s called “depredation.” Scientists think the whales are responding to the sound of boats being put into gear.
“It’s kind of like a dinner bell, and they can hear that from 10 miles away and come running right over to your vessel,” said Tory O’Connell, operations manager at the Sitka Sound Science Center.
She says the grant money will establish a bioacoustics lab in Sitka, where scientists will study the distinct noises sperm whales make when they’re munching on someone’s catch. She calls it a “creak-pause.”
“When whales are actually about to take a fish off a longline, they make a noise that’s called a creak,” she said. “It sounds like a door creaking open in a horror movie. And if that’s followed by a pause, there’s evidence that that is a depredation event. They’ve stopped doing all that noise because they’re now going after a fish.”
Researchers are going to count the creak-pauses they hear, and figure out how often the sperm whales are picking fish off the lines. And once they know that, the scientists and the commercial fishermen can begin coming up with ways to prevent it from happening.
“We’re not trying to scare them off completely, we’re just trying to discourage them from interacting with our gear,” said Dan Falvey, a commercial longliner for more than 30 years. “What you do find is a large number of straightened hooks, you find some fish that are bitten in half or have obvious tooth marks in them, and a lot of time you just get a couple of heads here and there on the line. Pretty obvious that something big has been feeding on the fish.”
Falvey says the sperm whales have only started picking food off the lines recently, since the fishing season switched to a quota system.
“Before that, the blackcod fishery off of Southeast, in the early 90s, was only open for a couple of weeks a year,” Falvey said. “I guess the whale population just wasn’t big enough to be up here and have any effect by then. But now that we fish nine months a year, we’re fishing during the time that the sperm whales are migrating up here to Alaska.”
O’Connell, back at the science center, says the program will hopefully find ways to prevent the whales from messing with the longlines, but that it also has benefits beyond the fleet.
“We will be doing active, meaningful, local research. So this is going to directly benefit our local fleet, it’s going to directly benefit the stock-assessment scientists that work on sperm whales, and it’s a collaboration between government scientists and fishermen,” she said. “So it’s really what the science center is about.”
And she says it will have educational benefits, too. Science center staff already have talked about having science students from local high schools learn how to process the acoustic data.
In addition to the Sitka Sound Science Center, the program includes the Scripps Institution of Oceanography, the University of Alaska Southeast, the Alaska Longline Fishermen’s Association, and the Auke Bay Laboratories Ted Stevens Marine Research Institute.
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