Megamouth shark

What it is

This shark has a soft, flabby body and a broad, bulbous head. Its colour is dark brownish-black or grey on top and white underneath. The most striking feature is its large mouth, which can reach 1.3 metres in width. Inside, the upper lip has a brilliant silvery-white band. It has small, peg-like teeth arranged in many rows. The tail is asymmetrical with a long upper lobe. It lacks the caudal keels found in faster sharks, reflecting its slow swimming style.

Where it lives

Specimens have been found in the Pacific, Atlantic, and Indian Oceans. Most records come from Japan, the Philippines, and Taiwan. Sightings also occur near Hawaii, California, Mexico, Indonesia, Australia, Brazil, Senegal, South Africa, Puerto Rico, Ecuador, Peru, and Panama. They inhabit deep waters, reaching depths of 1,500 metres. During the day, they stay deeper, often between 120 and 700 metres. At night, they ascend to shallower waters, sometimes near the surface, to feed.

How it lives

The megamouth is a slow swimmer, moving at roughly 1.5 to 2.1 kilometres per hour. It feeds by ram filtration, swimming with its mouth open to catch plankton. Its diet includes krill, jellyfish, and various larvae. The silvery lip may reflect light to attract prey or help sharks identify each other, though it does not produce its own light. Electrosensory pores on the head help detect prey. Recent tagging shows they migrate vertically daily and may move seasonally, though patterns vary between individuals.

Breeding and life cycle

Reproduction is ovoviviparous, with eggs hatching inside the mother. Genetic analysis of samples from Taiwan and Mexico shows no diversity between distant populations. This suggests a single, highly migratory global population that interbreeds freely. Footage from 2022 showed a male trailing a female, which may indicate courtship behaviour. Such social interactions were previously unknown for this solitary-seeming species.

Fish and people

Humans rarely encounter this shark. Since its discovery in 1976, fewer than three hundred specimens have been observed or caught. It was first found entangled in a navy vessel's sea anchor off Hawaii. While generally studied for science, some fishermen in the Philippines and Taiwan have caught and eaten them. They are occasionally mistaken for young orcas due to their shape and colouring. Their rarity makes them a significant subject for marine biological research.

Status and threats

Conservation status is not formally assessed in the provided text. However, their extreme rarity and low encounter rate suggest they are not abundant. Threats include accidental capture in fishing gear, as seen in historical records. Climate change and ocean pollution could impact their plankton food sources. Their slow reproduction and deep-water habitat make population recovery difficult if numbers decline. More data is needed to determine specific risks.

Questions people ask about Megamouth shark

Good reading and sources

• Megamouth shark on WikipediaEncyclopedia
• More photos on Wikimedia CommonsPhotos
• Wikidata recordOpen data