Laid-Back Lifestyle: Exploring the Relaxing World of Moonfish, The Laziest Fish

An adult moonfish reaches a size of 3.5-5.5m, weighs nearly 2,000kg, but the fry hatch out like a small pebble. Vietnam ranks moonfish as a rare species, listed in the Red Book and in urgent need of protection.


The moonfish (Nomenclature: Mola mola (Linnaeus, 1758) is a fish of the family Moonfish in the order Pufferfish (Tetraodontiformes). This fish has a rather strange shape. Overall, they have a rounded oval body in the front and flattened towards the tail. The length of the body can reach from 3.5-5.5m but it looks short as if it has no tail.

An adult moonfish

Moonfish have one fin on the back that protrudes like a shark and one close to the anus. These two fins are located almost symmetrically. Meanwhile, the caudal fin is short but surrounds the back of the body, looks like a narrow band, has little effect on swimming.
Adult moonfish usually do not swim, but float with the water

A special feature of this fish is that although the body is very large, the mouth is very small. Each jaw has two joined teeth that make the mouth look like a beak, so they can’t swallow large prey, but only eat small crustaceans and other plankton.
The feature of the large body but the short tail makes the moonfish very weak at swimming

Nearly all of the time, moonfish let their massive bodies drift freely with ocean currents. Perhaps because of this feature, the sunfish is also known as the sunfish because many people believe that they “bathe in the sun” on the surface of the sea.
But the most surprising thing about this fish is the baby moonfish larvae. A mother sunfish can lay up to 300 million eggs after just 3 weeks of pregnancy.
The fry when hatched are only slightly larger than a small sandstone, 600 times smaller than the mother’s body and have no resemblance to the shape of the parents. However, juvenile fish larvae grow very quickly, only 15 months after the eggs hatch, they can grow up to 373kg.
moonfish larvae

The eggs are fertilized externally and are easily swept away by ocean currents, so scientists have spent many years searching for baby moonfish and identifying the offspring of separate moonfish species.
The International Union for Conservation of Nature (IUCN) classifies moonfish as vulnerable

When young, moonfish, like many other fish, swim very well in schools. Until they grow up, they become more and more lazy, live alone and let their bodies float along the ocean currents to all the oceans.
When feeding, they lean over to swim and dive very quickly, then let their bodies drift away.
Vietnam ranks moonfish as a rare and precious fish, listed in the Red Book and in urgent need of protection; The law completely prohibits fishing and exploitation activities in any form.

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