Conger eel: the resident of Middle Rock

Most fish move off when you arrive. A conger looks back at you. That is what unsettles people the first time — you put your torch into a crack at Middle Rock and there is a head the size of a fist, mouth working steadily, entirely unbothered.

What it is

Conger conger, the European conger. Scaleless, grey-brown to near-black, with the dorsal fin running most of the length of the body. It is the largest eel in these waters by a distance — they can pass two metres, and the record fish are considerably more, though what you meet on a Clare reef is usually well under that.

The head is the part that looks wrong: broad, blunt, with a jaw that closes on solid muscle rather than teeth designed for cutting. They are not built to slice — they are built to grip and twist.

Why the same hole, year after year

Congers are site-faithful. A good crack — deep, dark, a tight fit, with the reef edge and open water within reach — is worth holding, and an eel that finds one will use it for a long time. That is why divers who know a site talk about the conger at a particular spot as though it were a specific individual. Often it is.

They are largely nocturnal, so what you see by day is a fish at home, not a fish hunting. At night it comes out and works the reef for fish, crab and octopus. That difference is worth holding on to — the animal watching you from the crack has nothing to gain from you and is not going anywhere.

The one thing that makes them dangerous

Not aggression — congers do not come after divers. The problem is feeding, and the problem is us. Where divers have hand-fed congers, the eels learn to associate a diver with food and come out to meet the next one. A large eel that arrives expecting fish and finds a gloved hand can do serious damage, and because the bite is a grip-and-twist rather than a clean bite, the injuries are bad.

Do not feed them, and keep your hands out of cracks you have not looked into. Both rules are for the eel as much as for you.

Give it a metre, keep the torch off its face after the first look, and it will simply sit there. That is the whole encounter, and it is a good one.

The strangest part of their life

No conger has ever bred in Irish water, and none ever will. When the time comes — and it comes once — they leave the coast entirely and swim out into the deep Atlantic, thought to be the Sargasso Sea region, thousands of kilometres away. On the way their bodies change: they stop feeding, the digestive system degenerates, the skeleton demineralises to release calcium, and the eyes and gonads enlarge enormously.

They spawn once and die. The larvae — flat, transparent, leaf-shaped things called leptocephali, so unlike an eel that they were first described as a separate animal — drift back on the currents over a year or more, and eventually a small conger arrives on a reef off Clare and starts looking for a crack.

So the eel at Middle Rock hatched somewhere in the mid-Atlantic and made its own way here. It is worth thinking about the next time you look into that crack.

Diving Middle Rock

It is a boat dive and it wants settled conditions, like most of the ground off this coast. Bring a torch — congers are in the dark parts of the reef and you will swim past them without one. Conditions for Kilkee are live on our home page, and we run the site regularly through the season.