The ocean sunfish is a weighty bony fish -[color=#0000FF]- the weightiest bony fish anywhere, at more than a ton on average. They tend to be anywhere from close to 6 feet long to nearly 11 feet.
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The fish spends large chunks of its time, about half of its day, just floating at the surface of the water, the purpose of which was a bit of a puzzle until now, BBC Earth reports.
This picture offers a bit of scale on the size an ocean sunfish can attain. The sunfish shown here was caught in 1910 and weighed an estimated 3,500 pounds.
U.S. LIBRARY OF CONGRESS, PRINTS AND PHOTOGRAPHS DIVISION
Researchers from the University of Tokyo attached to several sunfish both thermometers and cameras, to get an idea about changes in the their body temperature during their activities and to get a better look at what they might be eating.
The team found the fish were using their sun-worship time at the surface in order to get warm enough to go deep-diving for food. The scientists noted the fish cyclically warming itself and then heading to the depths to forage.
And what were the sunfish consuming at the chillier depths? While it's typically been the assumption that ocean sunfish prefer jellyfish, the team observed the giant fish dining on marine hydrozoans -- small, predatory relations of the jellyfish. They found their favorite of this fare between 160 and 650 feet down.
Once they finished foraging, the team observed, the sunfish would swim back up top to get some more sun and amp up their body temps yet again.
SOURCE:http://news.discovery.com/animals/giant-fish-sunbathes-to-warm-up-for-deep-dives-150209.htm
As gigantic as the ocean sunfish can be, it still seems like only half a fish.
Sunfish, or mola, develop their truncated, bullet-like shape because the back fin which they are born with simply never grows. Instead, it folds into itself as the enormous creature matures, creating a rounded rudder called a clavus. Mola in Latin means "millstone" and describes the ocean sunfish’s somewhat circular shape. They are a silvery color and have a rough skin texture.
The mola are the heaviest of all the bony fish, with large specimens reaching 14 feet (4.2 meters) vertically and 10 feet (3.1 meters) horizontally and weighing nearly 5,000 pounds (2,268 kilograms). Sharks and rays can be heavier, but they're cartilaginous fish.
Mola are found in temperate and tropical oceans around the world. They are frequently seen basking in the sun near the surface and are often mistaken for sharks when their huge dorsal fins emerge above the water. Their teeth are fused into a beak-like structure, and they are unable to fully close their relatively small mouths.
Ocean sunfish can become so infested with skin parasites, they will often invite small fish or even birds to feast on the pesky critters. They will even breach the surface up to 10 feet (3 meters) in the air and land with a splash in an attempt to shake the parasites.
They are clumsy swimmers, waggling their large dorsal and anal fins to move and steering with their clavus. Their food of choice is jellyfish, though they will eat small fish and huge amounts of zooplankton and algae as well. They are harmless to people, but can be very curious and will often approach divers.
Their population is considered stable, though they frequently get snagged in drift gill nets and can suffocate on sea trash, like plastic bags, which resemble jellyfish.
SOURCE:http://animals.nationalgeographic.com/animals/fish/mola/
http://oceansunfish.org/
