Mud-sucking mullet

Mud-sucking mullet

There are three species of mullet around the coasts of Britain and Ireland – the thick-lipped, thin-lipped and golden-grey. The thick-lipped is the most widespread.

It has four to seven silver-grey bands spanning its streamlined flanks and two small dorsal fins along its grey-blue back; the front fin has four stiff spines. The mullet’s underside is white, and its tail is forked.

An unmistakable identification feature of this fish is its thick front lips which contain sensitive nerve projections (called papillae) which may help it locate food.

Great survivors

The grey mullet can survive in places where other fish would soon perish. For example, it can withstand pollution, low levels of salinity (in estuaries) and oxygen-depleted waters.

The thick-lipped grey mullet stays in deep, warmer waters in winter and moves inshore as late spring approaches. In summer it can be found in estuaries, but it doesn’t travel as far up river as the thin-

Ever-filtering mullet

The mullet also feeds by filtering food particles through its gill rakers. Mud and debris are expelled while the edible matter is quickly coated with a layer of mucus and then swallowed.

The fish has yet another method of feeding: it skims the surface of the water, sucking algae or whatever edible food is available. Rocks, ropes and stanchion pier posts covered with algae also receive attention from the mullet.

You can catch it with a variety of baits including bread, mussels, ragworms, or small cubes of mackerel. The lips of a mullet are soft, but its mouth is hard, and it fights well. You need to play the fish firmly but patiently. Bullying it often causes the line to break or the hook to pull free.


The thick-lipped grey mullet spawns in the spring near the coast. Numerous eggs are shed and then fertilized. After about a week the eggs hatch, and the young begin to feed on plankton, swimming farther inshore for safety reasons. You can sometimes see them stranded in rock pools. After one year the young are 3in (7.5cm) long. They mature in four to five years, growing quickly in the warm coastal waters. lipped mullet. Harbours, bays and shallow, rocky shorelines usually have substantial numbers. Overall, it prefers relatively sheltered areas – away from strong tides.

A distinctive difference

A mullet doesn’t usually compete with other fish for food. Its diet consists mainly of diatoms (a form of plankton), plants, algae, tiny crustaceans and small worms and molluscs. It is also thought that, given the opportunity, it will eat sewage. Holiday-makers in tourist areas drop bits of chips or bread into the sea, providing another source of food for mullet.

A mullet feeds in unique ways. In one method (ingestion) it finds a muddy bottom, points its head and mouth downwards (its body rising up towards the surface) and sucks and swallows a mouthful of mud and tiny organisms. Many studies suggest that about 15-20% of what a mullet takes in is edible plant or animal life. The rest (80-85%) is mud or sand.

To cope with eating all this mud, it has a gizzard-like stomach. This thick-walled, muscular stomach (along with the mud and small stones) helps to grind up the food particles. The mullet also has an exceptionally long intestine which makes absorption of nutrients and disposal of waste materials much easier. A 12in (30cm) fish, for example, has an intestine about 6-7ft (1.8-2. lm) long. As the cold winter approaches, a mullet tends to stop feeding until the water warms up again.