Sperm whales may have learned to rustle sablefish

ANCHORAGE, Alaska – Years ago, the sound of a boat sometimes spelled death for the heavily hunted sperm whale. Now, some of them have figured out, it means dinner.

Scientists recently figured out that sperm whales in the Gulf of Alaska zero in on boat engines to locate miles of fishing lines hung with valuable sablefish.

“That’s the whales’ cue,” said Jan Straley, an assistant professor at the University of Alaska Southeast who since 2002 has helped lead the study.

Sperm whales don’t tune in to just any engine noise to track what are essentially miles of sablefish shish kebabs. The endangered whales key in on the engines’ sporadic bubbling as fishermen turn them on and off while hauling in longlines, the ongoing study said.

The work has led researchers to recommend some low-cost ways for fishermen to hoodwink the highly intelligent cetaceans.

The researchers estimate there are 90 male sperm whales feeding from longlines in the eastern Gulf of Alaska, part of the world’s largest sablefish fishery. The whales leave behind partially chewed bodies, dismembered lips or nothing at all on the hooks.

Scientists found the sperm whales tend to feed on longlines in the late spring through summer, during the height of the sablefish season.

Sound receivers attached to the longlines recorded the loud clicks of chattering whales. Using the recordings, scientists found that whales dive shallower than normal when near boats hauling up the bottom-dwelling sablefish.

“The whale doesn’t have to dive as deep to get its food,” said Aaron Thode, an associate researcher at the University of California, San Diego, who is also leading the study, which is funded by the federally established North Pacific Research Board.

Fishermen fear the problem could intensify as the endangered marine mammals increase in number and teach each other the techniques of sablefish rustling.

Thode and Straley’s suggestions for fishermen include fishing earlier or later in the season, hauling in the line without changing engine speed, or making decoy noises with the engine to draw whales to a different area.

Fishermen said they will try the methods this season, but many believe the large-brained whales are just too smart.