Leaning over the parapet of the bridge on a summer evening watching the mullet lazily shoaling in the river below was a pleasant experience. The tide was full-in and the flooding seawater mixing with the fresh river water resulted in murky conditions.
There were dozens of the big fish milling about in the shallow water. They splashed loudly attracting the attention of other passers-by to watch them. Why they splash loudly is unknown, but it is a common behaviour among mullet.
About 100 species of mullet have been described worldwide; in Ireland we have just three species: the Thick-lipped Grey Mullet that is very common and widespread, the rarer Golden Grey Mullet and the Thin-lipped Grey Mullet.
The ones I was watching were the common Thick-lipped Grey Mullet. At times some of them broke the surface of the murky water to reveal their paler, extraordinarily thick and swollen-looking upper lips as shown in the image above. These prominent lips give the species its common English name together with 'grey' to distinguish them from members of the red mullet family.
The Thick-lipped Grey Mullet has an elongated, streamlined, cylindrical-shaped body, a broad, flat head, a forked tail and two dorsal fins that are widely separated. The back is a bluish-grey in colour with a greenish tinge. These colours pale and fade down both flanks, first turning silvery grey and eventually grading to white on the fish's belly.
The scales on the back and flanks are usually in that they are streaked, the individual streaks lining up to form six or seven longitudinal stripes running along the fishes' mid and upper sides.
Thick-lipped Grey Mullet spawn at sea in inshore waters. The eggs are laid in open water. The young feed on animal plankton. Juveniles and adults leave the sea and venture into estuaries and up rivers to feed on algae and small organisms. They feed both by sucking at the surface and by sifting among lose organic debris on the bottom.
Since mullet live in shallow waters close to the shore and enter estuaries and rivers, these fishes have, since antiquity, been caught by people as a source of food. They are valued both as a food fish and as a game fish.
Passing the parapet an hour later, I noted that the tide had turned and was now ebbing, all of the fish had gone, and the trickling river water was now crystal clear.