Sperm whale caught pilfering fish

Animal snatches catch from longline

Posted: Thursday, March 29, 2007

ANCHORAGE - The thief moved with supreme delicacy in the dim light, boldly attempting a quick heist before retreating into the watery shadows, but not before tape from a nearby camera captured the culprit's massive flippers and capsule-shaped head.

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More than enough for an ID.

The yawning mouth and thin lower jaw could only belong to one of the deep sea's giants - a sperm whale - caught snacking on oil-rich sablefish, or black cod, from a commercial fishing line in the eastern Gulf of Alaska.

Fishermen and scientists have known for at least two decades that the whales were snatching small numbers of fish from miles of longline in the world's largest black cod fishery. But last spring was the first time they actually caught one of the wily leviathans in the act.

The 45-second recording begins with the signature rapid-fire clicks of a sperm whale before the animal, most likely a male, swims into view and clamps down gently on a longline. Seconds later, a two-foot-long black cod pops off a nearby hook like a charm lost from a bracelet. The whale then releases the line and floats out of sight followed by the dead fish.

The whale moved with surprising grace and deliberateness, gently plucking the line like a guitar string, said Jan Straley, an assistant professor at the University of Alaska Southeast.

"The video showed they are very intelligent," said Aaron Thode, an associate researcher at the University of California, San Diego. "Now we want to see if all whales do same thing or use different strategies."

The camera was mounted on a longline baited with two black cod. At first, the large-brained whales were wary of the device, Thode said. Only after scientists camouflaged the device in a tangle of rope and dead fish did the whales approach.

Straley and Thode's research is focused on coming up with benign techniques for fishermen to deter the whales. Through his acoustic research, Thode verified last year that the whales key in on the sporadic bubbling of fishing boat engines to locate what amounts to miles of subsurface shish kebab.

The sweet, flaky flesh of the black cod, long prized in Japan and Hawaii, is gaining popularity in the mainland U.S., where it is also listed on menus as butterfish.

Straley and Thode think the footage, taken in clear waters up to 350 feet deep, may be the first to document a feeding sperm whale. Usually the animals dine on giant squid and other fish in the pitch-black depths thousands of feet below the surface.

The scientists estimate there are 100 mostly male sperm whales feeding from longlines in the study area from the south end of Baranof Island to the town of Yakutat. The whales leave behind partially chewed bodies, dismembered lips and sometimes nothing at all.

Fishermen and fisheries managers say the overall economic loss to the gulf's 410-boat sablefish fleet is probably low, but has increased in the past decade.

Fishermen fear the problem could intensify as the endangered marine mammals increase in number and teach each other the techniques of sablefish rustling. Once a prime target of whalers, scientists suspect sperm whales are recovering in oceans worldwide, although there are no definitive population numbers.

The National Geographic Society, which helped pay for the video equipment, has exclusive rights to the video and has no immediate plans to air it, according to Heather Cabral, spokeswoman for the society's licensing department. The researchers are hoping to collect more footage this summer with the society's help and may try to attach a camera to a whale's body, Straley said.



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