Grey mullet found in Irish waters comprise three closely related species: thick-lipped grey mullet, thin-lipped grey mullet and golden grey mullet. The three species, which look very similar to each other, all have strong, streamlined, silvery bodies with dark streaks, with large scales, a flattened head and two dorsal fins, the first of which has four small spines. Grey mullet are a coastal fish usually found in estuaries and brackish waters, where they like to graze on algae and gulp up detritus from the sea floor to feed on organic matter and invertebrates. They can be often seen in schools cruising through harbours or along piers close to the surface.
Thick-lipped grey mullet (Chelon labrosus)
The thick-lipped grey mullet is the best known in Irish waters. It can be distinguished by the pectoral fins either side of its head, which are long, pointed and reach past the pupils of the eyes when folded forwards. It has a reputation among anglers as a strong sport fish that is wily and difficult to hook and land.
Golden grey mullet (Chelon auratus)
The golden grey mullet has become more common in Irish waters in recent years, possibly due to ocean warming that has allowed it to expand its range northwards. As well as a distinct gold-coloured patch just behind the eyes, the golden grey mullet can be distinguished by the pectoral fins either side of its head, which just reach the eyes when folded forwards.
Thin-lipped grey mullet (Chelon ramada)
The thin-lipped grey mullet is a relatively lesser-known species and is not as frequently caught in Ireland compared with the other grey mullet. It can be distinguished by the pectoral fins either side of its head, which do not reach the eyes when folded forwards. The thin-lipped mullet is one of the species of interest for the DiadES project on ecosystem services provided by diadromous fish.