By NAOYUKI MORI/ Staff Writer
January 12, 2024 at 07:00 JST
Researchers for the first time captured video footage of a humpback whale foraging and “snacking” on fish that escaped capture from a fishing fleet.
The footage was released in the online edition of the international academic journal Ethology in November by Takashi Iwata, 40, an assistant professor of animal ecology at the graduate school of Kobe University, and his colleagues.
Humpback whales inhabit waters around the world, including off the Japanese archipelago. Adults can measure 15 meters and weigh 40 tons.
To catch prey, humpback whales normally lunge at schools of fish and plankton.
The survey was carried out in January 2017 in an area off northern Norway where sightings of humpback whales are common.
Compact cameras and other devices to record whales’ traveling speeds and diving depths were applied with the help of suction cups to the backs of three females swimming along the coast.
The systems are designed to naturally peel off and float to the surface within 10 hours or so, allowing them to be tracked and recovered based on radio waves from transmitters.
Analyzing the collected data, Iwata discovered that one of the three whales spent 43 minutes close to the fishing boats, during which time it gorged on herring and cod that dropped from fishermen’s nets while they were being hauled out of the ocean.
Orcas, a natural enemy of whales, were also spotted in the vicinity feasting on the fish.
Iwata said it was the first footage to capture humpback whales preying on “missed fish,” something that dolphins, seals and seabirds routinely do when fishing fleets are around.
“The humpback whales seemed to gather around the fishing boats so they could feed with ease,” Iwata said.
Given that the volume of fish that went overboard was not nearly enough to satisfy the marine mammal’s huge appetite, Iwata speculated that the whale pecked at the fish as a “snack.”
Iwata couldn’t help pointing out the risk of whales getting tangled in ropes, nets and other fishing tackle on such occasions.
“It would be better if steps were taken to produce loud noises underwater to keep whales away during fishing operations,” he said.
PHOTO CAPTION
A humpback whale, center, gorges on dropped fish below a fishing boat, upper right, while orcas, lower right, eye the pickings. (Photo taken by Andreas B. Heide and provided by Takashi Iwata, an assistant professor of animal ecology at the graduate school of Kobe University)
VIDEO CAPTION
A humpback whale scavenges for food beneath fishing boats. (Video footage taken by Andreas B. Heide and provided by Takashi Iwata, an assistant professor of animal ecology at the graduate school of Kobe University)
A peek through the music industry’s curtain at the producers who harnessed social media to help their idols go global.
A series based on diplomatic documents declassified by Japan’s Foreign Ministry
Here is a collection of first-hand accounts by “hibakusha” atomic bomb survivors.
Cooking experts, chefs and others involved in the field of food introduce their special recipes intertwined with their paths in life.
A series about Japanese-Americans and their memories of World War II
