HONOLULU, Dec. 23 (UPI) -- Researchers trying to cut down on the number of false killer whales being caught in longline fishing gear in the Pacific have captured video of the marine mammal's attempts to remove fish from the line.
In the video, the false killer whale successfully removes three bait fish from the line, a behavior called depredation, though frequently the animals are hooked for their effort. The problem happens consistently enough that the U.S. government deemed the problem an unsustainable one for the species and has undertaken research efforts to preserve the marine mammals.
For longline fishing, commercial fishermen use lines 19 to 37 miles long to hook fish. Researchers used a camera, sound recordor and vibration sensor on a line cast by a fishing vessel off the coast of Hawaii.
The false killer whale, which is actually a member of the dolphin family, can be heard making a distinct clicking and whistling sound as it approached a baited fishing line intended to reel in game fish such as yellowfin tuna and mahi mahi, part of the false killer whale's diet.
In a paper published in the Journal of the Acoustical Society of America, Scripps Institution of Oceanography at the University of California San Diego scientist Aaron Thode wrote the distinct noises made by the false killer whale as it approached the baited hook could be key to reducing the number of instances where they become entangled.
"Further acoustics studies could help us understand more about these animals' behavior, which could be used by fishermen to hear the animals make these whistles or echolocation noises before they deploy their gear," Thode said in a press release. "The study can also be helpful in designing future experiments to estimate the actual number of animals in the region."
Previously, Thode wrote, scientists were unsure whether the false killer whales were becoming entangled because they were hunting game fish already snagged or simply taking the bait.