Megamouth Shark

The WA Museum's megamouth specimen was the third specimen to be discovered. It is a 5.15 m long male shark. It washed ashore at Mandurah, 50km south of Perth, in August 1988.

The day before, it was still alive and drifting shoreward when surfers mistook the shark for a whale and tried to coax it into deeper water to prevent it being stranded.

Megamouth sharks feed on plankton and krill and live in very deep waters, rising towards the surface at night to feed.  It was preserved in formalin before being stored in ethanol in a below ground tank in the WA Museum in Perth.

As part of our ongoing efforts to preserve and care for our collections, the Megamouth was removed from ethanol and soaked in aqueous glycerol solutions for nearly three years.  As a result, our shark specimen is now more flexible, less shrivelled and has plumped up by 115kg, so now it weighs in at 484kg.

Megamouth sharks spend daylight hours near the edge of the continental shelf, swimming slowly at depths of 150 m or deeper. At night time it rises close to the surface to feed on small shrimp that form part of the plankton.

They are one of only three species of sharks that feed on plankton (planktivorous). They probably swim along with their mouth open, filtering plankton from the water as it passes through their gills. The other two filter-feeding shark species are whale sharks and basking sharks. Like these other filter-feeding sharks, megamouth sharks only have small teeth. Megamouth sharks are also able to thrust out their jaws (called protrusible jaws).

Megamouth sharks have soft bodies with large oily livers, flabby muscles and skeletons that are poorly calcified. These features probably help megamouth sharks to swim very slowly without sinking.

Little is known about how these sharks reproduce but they probably give birth to live young which have fed on unfertilised eggs in their mothers’ uterus. This is known as oophagy.

DNA studies suggest that megamouth sharks are the most primitive of sharks of the Order Lamniformes, the group which includes white pointer, mako, basking and grey nurse sharks.