It isn’t certain whether the red mullet exists as two varieties of one fish, or as two distinct species. Mullus surmuletus, 30cm (1ft) or more in length, is the species we recognize living in the waters off the south coast of Britain. The very similar Mullus barbatus, on the other hand, a smaller fish known to reach only 20cm (8in) long and lacking the yellow bands of the larger fish, does not reach the British coastline. Some people think that these two are just variations of one species.
The red colour distinguishes the red mullet from other mullet in British waters (such as the golden grey, the thick-lipped grey and the thin-lipped grey), as does its steep forehead and the two large barbels hanging from its lower jaw.
A beautifully coloured fish, the red mullet is reddish brown during the day with four to five yellow stripes and a darker stripe running from eye to tail. At night the stripes break up into an indistinct marbled pattern. Below a depth of about 15m (50ft) the fish stay a deep red.
Moderately slender, the red mullet has a blunt snout and large, thin, fragile scales. There are two short dorsal fins, the first spiny with a dark trailing edge and the other soft.
The lateral line is continuous and the tail is deeply forked. The eyes are moderate in size – with a colour reminiscent of the eyes of a teddy bear. The teeth, which occur in two rows on the lower jaw, are blunt and not very strong. There are no teeth on the upper jaw, but some are located on the palate.
The two barbels under the chin, usually in constant motion, can be laid back into a groove along the sides of the lower jaw. The fish uses them to search for food. They are covered in sensory pores which detect prey as the fish forages along the muddy sea bed, catching and eating molluscs, shrimps and worms. Sometimes the fish excavates a small pit to reach its target.
Red mullet migrate northwards during the summer. It is not known where British populations spawn, but in the Mediterranean Sea the female sheds her eggs on the sea bed in 10-55m (33-180ft) of water.
The eggs, with a diameter of 0.8-0.9mm, are pelagic. The larvae hatch in three to four days, and can be recognized by the yolk sac which projects forwards, well in advance of the head. An oil globule is sited at the extreme end of the yolk sac.
The young fish live among the plankton, near the sea surface. At this stage they have a blue back and silvery sides.
Living in small schools on sandy or muddy sea beds from 3-9m (10-30ft) deep, the adult red mullet is a highly prized food fish. It isn’t common enough in British waters, though, to make it viable for commercial fishing.
Fabulous prices are said to have been paid for this fish in ancient times. It was one of the favourite dishes of the Romans and is still sought after today by gourmets for its wonderful taste.