Mola mola, Linnaeus 1758

Identification

Unmistakable species due to its shape, presenting the rounded body with two fins in the posterior area projecting vertically in opposite directions. 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. The ocean sunfish is a very large, oddly shaped fish that gets its name from his habit of floating on its side, at the sea surface, warming itself in the sun
They are a silvery color and have a rough skin texture. Their teeth are fused into a beak-like structure, and they are unable to fully close their relatively small mouths. They are clumsy swimmers, waggling their large dorsal and anal fin to move and steering with their clavus.

Biology

It is the heaviest bony fish in the world, reaching weights of up to 2300 kg, and the distance from the top of the dorsal to the bottom of the anal fin can be as much as 4m. Sharks and rays can be heavier, but they’re cartilaginous fish. Mola are found in temperate and tropical oceans around the world. Their food of choice is jellyfish, though they will eat small fish and huge amounts of zooplankton and algae as well. The reproductive behaviors of ocean sunfish are not well known, but they reproduce via broadcast spawning, where females release eggs and males release sperm into the water column at the same time. This behavior increases the likelihood that eggs will become fertilized and that fertilized eggs will not be eaten by egg predators.They can release as many as 300 million eggs at a time and spawn several times throughout their lifetimes. They can reach 10 years old.

Behaviour

They are frequently seen basking in the sun near the surface and are often mistaken for sharks when their huge dorsal fin emerge above the water. 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 the air and land with a splash in an attempt to shake the parasites. They are harmless to people, but can be very curious and will often approach divers.Their population is considered vulnerable. Sunfish frequently get snagged in drift gill nets and can suffocate on sea trash, like plastic bags, which resemble jellyfish.
Ocean sunfish are generally solitary, unless while being cleaned in a group.

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