Sperm Whales Use Boat Engines As Cues To Dine On Longline Bait

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ANCHORAGE, Alaska — Sperm whales in the Gulf of Alaska are likely using the sounds of fishing boat engines as underwater dinner bells to hone in on longlines hung with valuable sablefish, scientists said. The engines make loud, erratic bubbling noises as fishermen maneuver their boats while winching up hundreds of bottom-dwelling sablefish. "That's the whales' cue," said Jan Straley, an assistant professor at the University of Alaska Southeast who since 2002 has helped lead an ongoing study of the whales' behavior.

Scientists estimated 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 dive shallower than normal when near fishing boats, the study said. Sound receivers attached to the longlines recorded the loud clicks of chattering whales. Scientists used the recordings to gauge how deep the whales were diving and their proximity to the boats.

"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. The study also found that sperm whales tend to feed on longlines in the late spring through summer, during the height of the sablefish season. The season starts in March and ends in November.

These discoveries have helped researchers devise low-cost ways for fishermen to hoodwink the highly intelligent cetaceans. Their suggestions include fishing earlier or later in the season, hauling in the line without shutting down the engine, 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.

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