Sperm whales have learned to pluck sablefish hauled from the black depths of the Gulf of Alaska, showing a dexterity that belies their enormous size and toothy, underslung jaws.
"They somehow just pick them off like grapes," said Sitka longliner Dick Curran, who has fished the Gulf's deep waters for decades. "I don't know how they do it, and I don't know the depth. ... Sometimes you get the heads back, sometimes you just see lips, and sometimes they're just shredded."
Fishermen report they've seen whales floating near buoys marking the longlines with hundreds of baited hooks set on the sea floor, or waiting beside boats when crews rise after a sleep break.
"They would drift right close enough, just kind of lolling on the surface, so that if you could lean over the side far enough, you could reach out and touch them," said Linda Behnken, director of the Alaska Longline Fishermen's Association.
"They were like big logs around the boat."
No one knows yet how they're cueing into the Gulf-caught sablefish, also called black cod, whose oily, rich flesh has become a lucrative product in Japanese markets. But a coalition of commercial fishermen and biologists have begun to investigate with funding from the North Pacific Research Board. An important angle will be to look for fishing strategies that won't draw sperm whales to dinner.
"We don't want the fishermen to have an economic loss, plus it's a biological loss, because we don't know how many sablefish are being taken," said Sitka-based whale specialist Jan Straley, a lead investigator in the project. "My interest is biological, and I really want to understand what these whales are doing."
What Straley and her partners have found after one season suggests that male sperm whales may patrol the edge of the continental shelf, where the water is 1,200 to 3,000 feet deep, deftly snacking their way through the eight-month-long fishery like bachelors lurking over party hors d'oeuvres.
Their behaviour off Alaska's coast gave people a chance to study a complex ocean predator that has the largest brain of any animal ever known.
"For sure they know the sound of hydraulics engaging -- the whales definitely know that it's like ringing the dinner bell for them," said Behnken, whose group is a coordinator of the study.
"But they've gone one step beyond that. They've learned that the flag and bag (of the buoy) in the water is all part of that dinner bell. Everyone knows whales are smart, and they're proving it."
ENDANGERED BUT RECOVERING
Federal surveys confirm that sperm whales don't always pluck fish when they're around, Sigler said. When the whales do take fish, the catch rates decrease an estimated 20 percent to 25 percent.
"No one likes to get fewer fish, but take one look at those big whales and you realize you're out of your league," said Sitka longliner Dan Falvey, who, along with Curran, is one of 10 fishermen working with Straley.
"We'll set and there will be no sperm whales around, and we'll be coming out from our anchorage and there'll be two or three sperm whales waiting by the flag," Falvey said. "Sometimes they'll swim by the boat less than 40 or 50 feet away and stick their head out of the water and look at you with their big eyeballs, and just look at what's going on."
Sperm whales are the largest toothed cetaceans, ranging more than 35 tons and 50 feet long -- longer than a People Mover bus and three times as heavy. Their body is about 40 percent head.
Decimated worldwide by commercial whaling, the species is listed as endangered. Although biologists believe sperm whales have been recovering and are no longer in danger of extinction, no one knows how many frequent Alaska waters, said biologist Paul Wade at the National Marine Mammal Lab in Seattle.
NO WHALES HURT ON LONGLINES
Like other great whales, they find prey with their extraordinary hearing, able to perceive their environment with echoed clicks and other sounds. In other areas of the Pacific, sperm whales are known for taking 45-minute dives into the abyss to gulp giant squid. Yet Japanese whaling records following World War II found that Gulf sperm whales ate more fish, including small amounts of sablefish that inhabit waters nearly as deep as the squid.
Over the past few decades, some of the Gulf sperm whales apparently realized that fishermen were bringing this deep food source to the surface, and learned to remove a 20- to 30-inch fish from hooks. They also seem to enjoy what fishermen throw overboard after processing the catch.
"Until you actually have a fish that comes up with tooth marks in it, it's hard to tell if the fishing is slow or they're working over your gear," Falvey said. The depredation takes place "only about half the time when I see whales around. The rest of the time, they just float about 200 yards off and eat the heads."
The whales have yet to get seriously hurt or entangled in the sablefish gear, according to fishery managers and whale biologists. Yet the situation has the potential to put a largely unknown population of legally endangered animals at odds with what has become one of Alaska's most valuable fisheries.
"So far, it's been nothing but good for the whales," Behnken added. "I don't foresee that there is going to be any problems with the whales, but we want to head off any problems. ... And we'd like to teach the whales to catch their own fish."
In 2004, a fleet of 400 to 500 boats will have a quota of 23,000 metric tons, with two-thirds to be caught from the Gulf, Sigler said. The fish has brought $3 to $4 per pound delivered to the dock in recent seasons.
"It's the highest value finfish in Alaska," Sigler said.
To harvest black cod, fishermen sink a 2-mile-long line with baited hooks every three to six feet. Each end is anchored to the seafloor along the continental slope and buoyed at the surface. After an 8- to 12-hour "soak," fishermen haul the line, sometimes harvesting hundreds of sablefish in a single set.
STUDYING WAYS TO STOP THE THEFT
Sperm whales were first observed taking black cod in 1978 in the Gulf. But beginning in 1994, when fishermen received seasonal quotas and the fishery increased to eight months, the losses dramatically shot up. The whales, it was thought, had more time to learn and feed, and they took advantage of the slower-paced fishery.
"Sometimes as many as six whales would be around the boat," Behnken said. "When the whales dove, your catch rate would dive with it. It was pretty clear they were taking fish off the lines, and they're pretty good at it."
The fisheries group began talking to Straley and government managers about investigating the whales. With about $200,000 in funding from the research board, Straley helped launch the Southeast Alaska Sperm Whale Avoidance Project in 2003. Other investigators are Behnken, fishery manager Victoria O'Connell with the Alaska Department of Fish and Game and federal geneticist Sarah Mesnick with the Southwest Fisheries Science Center in La Jolla, California.
"The fishermen came to us and the managers and said, 'We have a real problem, and we want to be ahead of the curve,' " Straley said.
Some ideas might be to put a device on the line that might create noise or "clutter" that would keep the whales from finding the fish, or hauling lines at different times of day, Behnken said. But humans first need to learn more about the whales.
With volunteer fishermen keeping logs and taking photographs, Straley identified 17 different sperm whales interacting or visiting the longline fleet -- and four animals were seen more than once near boats. The whales were vocal, clicking intensely. Ten genetic samples taken from six individual whales found them all to be males. Previous sperm whale research suggests that females and calves might remain in warmer waters while male whales roam, but no one really knows.
Straley, who has spent years studying humpback and killer whales in Southeast's protected waters, said she first had to figure out a way to identify sperm whales and approach them on the open sea.
"Some of them were really, really huge, and others were just huge," said Steve Weissburg, captain of the boat that took Straley out to observe whales and take samples. "I think the easiest thing to say was they just flat out ignored us."
Straley was "totally awestruck" by the big whales.
"The behaviour I saw was amazing," she said. "If I had one wish, it would have been to have the ocean clear to see what they were doing."
Daily News reporter Doug O'Harra can be reached at firstname.lastname@example.org.