It’s been a banner month for rare shark sightings. Last week a fisher off the coast of Florida caught the second goblin shark ever seen in the Gulf of Mexico. Now reports out of Japan state that fishers have caught a 13-foot (3.9 meter) long megamouth shark, also incredibly rare, near Shizuoka, Japan (map).
This is only the 55th confirmed megamouth shark sighting since the first one was accidentally caught by a U.S. Navy research vessel off the coast of Oahu, Hawaii, in 1976. There have been several other dubious megamouth reports, says George Burgess, director of the Florida Program for Shark Research at the Florida Museum of Natural History in Gainesville. But since researchers couldn’t confirm those sightings, Burgess considers the tally to stand at 55, including this week’s haul.
— 保存食@シカ (@Onnyou) May 6, 2014
Staff at the Marine Science Museum in Shizuoka dissected the reportedly 1,500 pound (680 kilogram) megamouth (Megachasma pelagios) in a public presentation earlier this week (seen in the tweet above). The shark’s remains are on display at the museum, according to the Japan Daily Press. Fishers captured this female specimen in about 2,600 feet (792 meters) of water. (Watch video of the dissection.)
A Big Mouth
The megamouth shark’s most prominent feature is its large mouth—hence its common name. The animal uses its giant maw for filter feeding, much as whale sharks and basking sharks cruise the ocean with their mouths open, straining tiny animals called plankton out of the water, says Burgess. Small, shrimp-like animals called krill are believed to make up a large portion of the megamouth’s diet.
Records of the shark’s behavior come from observations of only two individuals. Researchers were able to affix a tag to one megamouth shark off the coast of California in 1990 and track it for two days. The male shark spent its days in 492 feet (150 meters) of water, ascending to 49 feet (15 meters) at dusk. This daily pattern of migrating up and down in the water is fairly common for open ocean animals of all sizes, says Burgess. The creatures are following food, he explains, as well as spending time in different water temperatures to maintain bodily functions like digestion or growth.
The second megamouth researchers observed was in the process of getting attacked by three sperm whales off the coast of Indonesia in 1998, according to the Florida Museum of Natural History.
The megamouth’s slow swimming speed and flabby body also make it an attractive target for other opportunists in addition to whales, such as the cookiecutter shark, Burgess says. This small shark sneaks up on animals in order to bite off chunks of flesh, leaving a crater-shaped divot behind. Some megamouths that have been examined showed evidence of scarring believed to be the result of attention from cookiecutter sharks.
A Hot Spot?
Although megamouth sharks have been found all over the world, “the area from Japan down through the Philippines and into Indonesia seems to be a hot spot,” says Burgess. This could be because the sharks are naturally abundant there, or it could be simply that, because the area is heavily fished, people are more likely to encounter a megamouth here.
Burgess’s opinion? “I think the reality,” he says, is that it’s “an area of abundance.” This part of the western Pacific Ocean, from northern Australia up to the Philippines, is thought by some researchers to be a cradle of evolution for marine animals. It’s “an absolute honey hole of diversity,” he adds, and it could be the place of origin for the megamouths.
With every megamouth shark that comes to light, scientists learn more and more about this mysterious animal. Burgess just wishes most of the sharks didn’t end up dead.
“It’s a win-lose situation,” he says. “We’re happy to get another individual to study and add to our knowledge base—but regrettably, we’ve gotten to the point where we’re killing these things.” All but one or two megamouths were dead by the time scientists got to study them.
“Much as I would love to have a sample size of 200 or 300 of these [sharks],” Burgess says, “we want to encourage fishermen to send them back overboard and just take a picture of them.”
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