Sperm whales have learnt a way to snatch cod from the fishing lines cast out by industrial fishing boats close to Alaska. This is called “depredation.” To achieve this, sperm whales use their long jaws to create tension on the line, which in turn snaps fish off the hooks.Stephen Rhoads, a boat skipper who has been fishing in the area for 20 years. told the BBC recently: “That they’re getting better at this every single year and it’s less work for them to hang out with us and take our fish than it is to dive down and get them off the bottom. There’s no doubt that these creatures are very smart.”
The problem is, this behavior can lead to whales becoming entangled in fishing nets. Worried about this, several fishermen from the Alaska Longline Fishermen’s Association have collaborated with a team of scientists, from the Sitka Sound Science Center, to devise a way to harmlessly send whales away from the nets. The newly devised decoy uses a sonic signal.
Sperm whales (Physeter macrocephalus) are the biggest of the toothed whales. Mature males average 16 meters (52 feet) in length, and the whales can be found in most parts of the world’s oceans.
The new device, according to Science News, is an acoustic decoy that makes sounds that lure whales away from the fishing boats. Typically whales move 4 miles away from the boats. After successful trials, the device was presented at a recent meeting of the Society of Marine Mammalogy.
In related news, a new report has examined the effects of “ghost fishing” on marine life. This is where fish, crabs and other marine life are drawn into nets and traps by the dead and decomposing bodies of other creatures.
