A large Megamouth Shark, an extremely rare deepwater creature, was caught off the Japanese coast by accident by fishermen earlier this month. The one-ton fish got trapped and died in fishing nets approximately 5 kilometres (3 miles) from Owase Port (尾鷲市) in the Mie Prefecture in central Japan in the southeastern Kii Peninsula.
This 16.5-foot long shark, known by marine zoologists as Megachasma pelagios, weighed 2,000 pounds (907 kg). Local media say a fishmonger bought it in a fish market.
This Megamouth Shark, with its flabby muscles and weak skeleton, did not have the strength to escape from the fishermen’s net, and died. (Image: twitter.com/louoly_o0)
First discovered in 1975
We first knew about the existence of the Megamouth Shark in 1976. At first, most people thought it was a hoax. Only sixty-one specimens have ever been either caught or observed.
The Megamouth Shark is a filter feeder, and like its other two cousins, swims with its gigantic mouth wide open, filtering the water that comes in for plankton and jellyfish.
Its bathtub-sized jaws are big enough to swallow a human – its mouth can reach up to 4ft 3 in (1.3 metres) wide. It has about ninety tiny teeth that separate the edible portion of each mouthful from the inedible. It has two unusual sheets of silvery tissue hanging from its upper jaw. Scientists are not too sure what they are for – perhaps to attract prey.
The Megamouth shark is often mistaken for a young killer whale (orca) by observers.
Flabby fish with weak skeleton
Due to its nutrient-poor environment, the Megamouth has flabby muscles and a poorly calcified skeleton. This is no problem for an animal that moves slowly in deep water sucking in plankton. However, when caught in a fisherman’s net, it has little chance of escaping.
A human lies down next to the Megamouth Shark caught last week to give us an idea of its size. Most discoveries of this species have been in the equatorial regions of the Indian, Pacific and Atlantic Oceans. So few have been sighted or caught that we don’t know their exact habitat range. (Image: twitter.com/thegulftoday)
It has an alien-like appearance, with its bizarre rubbery lips, a big head and massive mouth.
Its tail fin is proportionally large. The upper lobe is half the length of its body, while the lower lobe is less well developed. Its dorsal fin, however, is surprisingly small.
It is so distinct from other kinds of shark that it is often considered to be the only surviving species in the family Megachasmidae.
Some marine zoologists believe it might belong to the family Cetorhinidae, of which the sole surviving member is the basking shark.
As far as sharks go, the Megamouth is among the larger ones. It can grow to 5.5 metres (18 ft) in length, and weighs up to 2,697 pounds (1,315 kg).
It has light-emitting organs which appear as luminous spots –photophores – surrounding its mouth. Scientists believe these act as a lure for tiny sea creatures, such as plankton and small fish.
Experts believe more than 61 sightings or captures of Megamouth Sharks have occurred. In many cases, fishermen did not know what it was, found it too large to handle, and placed the specimen back in the sea. (Image: twitter.com/Sharks4Kids)
In 1990, a large male – 4.9 metre (14 foot) long – Megamouth was caught off the coast of California, USA. A team of scientists who wanted to monitor it attached a small radio tag to its body.
Over a period of 48 hours, the tag relayed information on the fish’s swimming habits; providing useful data on how deep it went, and when.
The scientists in California reported that the shark swam down to a depth of between 390 and 520 feet (120 to 160 metres) during the day, but at night time it swam around at depths of between 39 to 82 feet (12 to 25 metres).
They also reported that this shark is a very slow swimmer – travelling at between 1.5 to 2.1 km/h (0.93 to 1.5 mph).
Many marine creatures that pursue plankton have a similar pattern of diving deep down during the day, while coming nearer the surface of the sea at night.
Regarding the Megamouth Shark, the Florida Museum of Natural History says:
“This rare and unusual shark has been knowingly encountered so few times that the scientific community has a list and extensive notes on each shark encountered. Due to the lack of information concerning distribution and population status, the megamouth is considered “Data Deficient” by the World Conservation Union (IUCN).”
“Although only 63 confirmed sightings of megamouth shark are reported, this species is now known from Indian, Pacific and Atlantic Oceans.”
Video – Ultra-rare Megamouth Shark caught off Japanese coast