Smallest Fish Species

The smallest fish species known to man is Paedocypris progenetica. The fish has a maximum length of 7.9 mm (.31 in).

Paedocypris Classification

The fish species belong to the Paedocypris. The carp belongs to this family too. Paedocypris micromegethes is also a part of the family. One was seen off Terengganu, Malaysia back in 2006. The fish has also been spotted in Sarawak.

Physical Characteristics

The Paedocypris does not possess the bony structure seen in other fish. The fish also keeps the post-anal larval fin fold. The fold is found along the caudal peduncle’s ventral edge. This part is often seen at the fish larvae.

The pelvic fins are another distinguishing trait of the male Paedocypris. At the end of the primary ray is a keratinized skin hook. It is supported by the hypertrophied pelvic musculature. The keratinized skin is also on the pelvic fin. Its purpose however, is still unknown.

There are several theories though. The most popular one is that it is used when mating. The male uses it to keep the female in place. Other researchers maintain that it is used to keep a place at a spawning surface.


The smallest fish species are found mostly in peat swamps in Sumatra. The Paedocypris micromegethes has been sighted at Sarawak, Borneo. It has been observed that both fish species are able to live even in droughts. Studies indicate that the fish can live in acid water puddles with 2.8 pH levels.

However, it is vulnerable to pollution and the destruction of its natural habitat. Majority of the time, the fish can be seen in the backwater streams.

When was the Paedocypris Discovered?

The species was discovered in 1996. The species were uncovered by Maurice Kottelat and Tan Heok Hui. Hui is from the National University of Singapore and Raffles Museum of Biodiversity Research. The name was taken from the Greek word paideios (“children”). Progenetica was taken from the word progenetic.

Anglerfish Photocorynus Spinicep

There are researchers who believe that anglerfish Photocorynus spinicep is smaller. There are reports some grow to lengths of only 6.2 mm. However, the species flourish only by sexual parasitism. It is also a fact that the female can reach lengths 50.6 mm.

Some scientists still have questions as to what the smallest fish species really is. It is possible that smaller fish are hiding in the ocean depths. Until they are discovered, the Paedocypris progenetica will be regarded as the smallest.

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