Big-mouthed megrim

Big-mouthed megrim

Some fishermen claim that, for a flatfish, the megrim exhibits some very odd behaviour. Not only has it been seen swimming at the surface – one report even suggests that it glides along using its tail fin and upper pectoral fin as sails.

However, when it isn’t aspiring to the Tall Ships Race, the megrim lives from 50-300m (165-985ft) deep on muddy, sandy or gravelly sea beds. It occasionally appears in depths of about 10m (33ft) but prefers offshore coastal waters facing the open ocean.

Megrim menu

This fish’s most distinctive characteristic is its curved mouth, which is enormous when compared with the mouths of other flatfish. This feature allows it to feed on smaller flatfishes and bottom-living creatures such as sandeels, dragonets and gobies, and on cod fish such as whiting and young haddock.

It also eats large numbers of crabs, deep water shrimps and squid. Surprisingly, sprats have also been found in its stomach, indicating that it probably leaves the sea bed to forage for food.

Although the megrim can grow to considerable lengths (up to 60cm/24in), its narrow, fiat body means it is not particularly heavy. Its body shape also leaves it vulnerable to capture in nets.

In northern waters and along the west coast of Europe, where it lives in abundance, trawling accounts for a substantial number of the megrim caught. Small numbers are also taken off Scotland’s west coast and off Cornwall.

The large eyes are oval and positioned on the left side of the head. They are separated by a bony ridge. Another distinctive feature is the long dorsal fin, which begins in front of the eyes and stretches right back, ending under the tail stalk.

Surface survival

The megrim breeds in spring (March to May). Those living in deep water at the far north of their range are the first to spawn. The transparent eggs, just over 1mm in diameter, float near the surface and hatch in five to six days.

Like the eggs, megrim larvae are transparent and continue to float near the surface of the sea — often covering vast areas — throughout the summer. By winter they have grown to about 20mm long and have developed adult colouring. At this stage they migrate to the sea bed and take up a bottom-living existence.

Their first eight to ten weeks of life, living near the surface, ensures that they are widely distributed. This reduces the concentration of the fish in specific areas and increases their chances of survival.