Electric rays paralyse their prey – using an electric jolt of up to 220 volts – before devouring them. By wrapping their winglike fins around an unsuspecting prey fish and discharging an electrical surge, they can stun into insensibility quite large fish.
Two species frequent British waters: the electric ray (the larger, at up to 150 lb/68kg) and the smaller, marbled electric ray which – in British waters – reaches a maximum weight of 13 lb (5.8kg) and rarely grows more than 45cm (18in) long. Neither is particularly common, but both have to be handled with extreme care if caught.
The electrical current (triggered by touch) only operates while the fish is alive and repeated discharges become progressively weaker. But the jolt, if you touch a large, live electric ray, is enough to knock you off your feet. There are even reports of anglers receiving a shock from their line before they’ve seen what’s on the end of it.
The organs that produce the electricity are situated just under the ray’s skin and run through the length of its wings. Although rays are neither fast nor strong swimmers, they can disable quite large fish with the knock-out charge. Victims of their shocking methods are mainly bottom-living fish such as rockling, whiting and dogfish.
Both rays have rather small mouths, but can swallow quite large fish once they have rendered them unconscious.
Electric rays are distant relatives of more common species such as the thornback, but are easily distinguished from them.
They have almost circular bodies and very smooth skin. The tail is thick and muscular with a broad, paddle-like tail fin. Both species have two dorsal fins near the tail, but the size and shape of these help to distinguish one electric ray from another. Both the marbled ray’s dorsal fins are almost identical in size, but on the electric ray the first fin is about twice the size of the second.
The easiest way to tell these fish apart is to look at their colour. The electric ray has a plain, much darker back than the marbled species – its skin is black, grey or very dark brown on top and white underneath.
The marbled electric ray, as its name suggests, has a distinct marbled pattern on its brown back and a cream underside.
Whereas most rays produce sacs full of eggs, the electric species bear live young. Their litters are generally small — rarely containing more than eight pups — and although young ones are occasionally caught in British waters, they are probably born in warmer seas.
Both electric and marbled electric rays appear in British waters in the summer and early autumn. They prefer relatively shallow waters 10-150m (30-490ft) deep -suggesting they migrate to warmer waters as the year passes.