Electric Ray

Electric Ray
  • Scientific name: Torpedo nobiliana (synonymous with Tetronarce nobiliana)
  • Also known as: Dark Electric Ray, Atlantic Torpedo, Sea Torpedo, Numbfish, Crampfish
  • Size: Up to 6ft in length and 200lbs
  • UK minimum size: N/a
  • UK shore caught record: 52lb 110z
  • IUCN Status: DD (Data Deficient)
  • Distribution: In British waters the electric ray can be found in parts of the English Channel, Celtic Sea and along the coasts of Wales, Northern Ireland and the west coast of Scotland.
  • Feeds on: Mostly feeds by hunting fish.
  • Description: Large ray with broad almost circular rounded body. Eyes are small with a pair of prominent spiracles just behind. Colour is olive green, brown to black, sometimes with purplish tinge. Skin is smooth and completely free of the small thorns and spines which are common to other ray species. There are two differently sized dorsal fins on the tail. Unusually for a ray its tail is not long and whip-like but instead ends in the type of tail common to most roundfish. Mouth is full of rows of small, sharp teeth.

Electric ray can grow to around six feet in length and weigh around two hundred pounds. However, this represents the maximum size of this species and the majority will be three or four feet in length and weigh between thirty and forty pounds. The are primarily a demersal (bottom-dwelling) species, but will also swim and hunt in mid-water and can be found in any water depth from the surface to over one thousand metres deep. They are nocturnal, spending the day partially buried under the sand of the seabed and coming out at night to feed. For the most part they are solitary creatures, only coming together to breed. Little is known about the reproductive patterns of the electric ray. They are thought to take long migrations, covering tens of thousands of kilometers over the course of their life.

Worldwide Distribution

Electric Ray Distribution

Map showing the world-wide distribution of the electric ray.

While there are around twenty ray species which are capable of giving an electric shock Torpedo nobiliana is the largest and the most powerful. It has a wide distribution, being found in warm and temperate waters off the coasts of North and South America, around Africa and throughout the Mediterranean. Despite many people seeing this species as exotic it is found in British waters to the south and the west of the British Isles with the western English Channel, Celtic sea and waters off the coast of Wales, Northern Ireland and the west coast of Scotland all being visited by the electric ray.

Danger: High Voltage

Electric Ray Electric Organs

Diagram showing the electricity generating organs in the electric ray.  The electric charge is generated via muscular contractions and stored in these organs, which can make up almost 20% of the rays total body weight.

Electric ray have two kidney-shaped organs electric organs in is body. These organs generate electricity through muscular contractions. This electrical energy is then stored in these organs in the same way as a battery. The electricity can be sent out of the body, allowing the ray to delivery a potent electrical shock to anything touching or getting near to it. A large electric ray, which has rested to allow its electricity to be effectively fully charged can give a shock of up to 220 volts. This is enough to knock a fully grown man off his feet, but is not enough to kill a healthy human, although it could potentially kill someone with underlying health problems. However, death could occur if a person is knocked unconscious by the shock, or injured to the extent that they could not swim and then drown. The ray uses its electrical ability as both a defensive measure and as a way of hunting food. Although the electric ray is sluggish and generally a poor swimmer it will use a short burst of speed to get near to a fish and then deliver the electric shock, stunning the fish and allowing the ray to attack it. If they can get close enough electric rays will wrap their wings around a fish to deliver multiple electric shocks and kill their prey outright. The electric ray has an expandable mouth which allows it to consume very large fish. Its electrical charge will also be used as a defensive measure to fend off large predators such as sharks which may attempt to attack it. Although rare, humans have been shocked when they have stepped on electric rays while walking through the sea near to the shore, and divers who think it is a good idea to touch electric rays often get a mild warning shock. It is actually thought that electric ray have two different types of shock – a small, light warning shock to discourage anything from getting to close, and a full power shock aimed to kill prey or attackers. This is because an electric ray can only hold a certain amount of charge in its electrical organs, and its most powerful shocks use up most of its electricity and the ray must wait some time to recharge itself. The smaller warning shocks allow the electric ray to ward off anything it sees as a threat while retaining most of its electricity.

 

Commercial Use and Rod Caught Electric Rays

Electric Ray Bycatch

An electric ray caught as bycatch by a trawler. Electric ray are of no commercial value and are thrown back overboard dead.

These days the electric ray has no value as a commercial fish. The flesh is gelatinous and to all intents and purposes inedible. This fish did have commercial value in the 1800s when its oil was used as both fish oil and as a source of fuel for lamps and lights. The oil of electric rays has been considered to be a cure of various different medical complaints for centuries. The Romans believed the oil could cure gout, while the Victorians rubbed the oil on skin in the belief it would clear up rashes and took it internally to cure stomach complaints. The ancient Greeks reportedly used the electric shocks from rays to numb people undergoing operations or even ease the pain of childbirth. Modern medical science has proved that electric ray oil offers no health benefits. Electric ray are caught as bycatch in trawls and thrown back into the sea dead. They are, very occasionally caught on rod and line, with the British record being a 52lb 10oz specimen caught off the coast at Porthallow, The Lizard, Cornwall in 1990. The state of electric ray numbers are not known. The IUCN (International Union for the Conservation of Nature) classes the electric ray as Data Deficient and more research is needed to work out more accurate numbers of this species.

Interesting Facts

The first written reference to electric rays comes from the work of the Greek philosopher Plato in the fourth century. In the Socratic dialogue Meno he described a discussion between Socrates and Menon in which Menon is so amazed by the arguments being put to him by Socrates he says:

“You are casting over me your spells and magic potions and words, and I am simply getting full of doubts. And if I may venture to make a jest upon you, you seem to me both in your appearance over others to be like flat sea torpedo, who torpifies those who come near him and touch him, as you have now torpified me, I think. For I am now benumbed in my soul and my mouth and I know not how to answer you.”

 – Meno by Plato. Translation from 1892.

It is thought that Menon’s comparison of being stunned by an electric ray leaving him speechless gave rise to using the term ‘stunned’ to refer to someone being shocked or amazed by a situation or a piece of news.

Robert Fulton

Robert Fulton (1765-1815), invented the first torpedoes as a naval weapon, and named them after the scientific name for electric ray.

Electric rays were given their scientific name of Torpedo nobiliana by the French biologist Charles Lucien Bonaparte in the 1800s. However, since the ancient Greeks were referring to this species as a torpedo it has clearly been used for thousands of years, predating the use of the term torpedo as a naval weapon by many centuries. The American engineer and inventor Robert Fulton is credited with inventing the first functioning torpedoes as a naval weapon. He used torpedo to describe an explosive charge which was towed behind the early submarines he invented. It is unknown exactly why he chose torpedo, presumably because he wanted to give his invention an intimidating name associated with a dangerous fish. This caught on and the term torpedo is now  the recognised word in the English language to describe a self-propelled weapon with an explosive charged launched under the water by modern submarines and other warships.

 

Marbled Electric Ray

Marbled Electric Ray

  • Scientific name: Torpedo marmorata
  • Size: Up to 4ft in length and 15lbs.
  • UK minimum size: N/a
  • UK shore caught record: 13lbs 15oz
  • ICUN Status: DD (Data Deficient)
  • Distribution: Southern North Sea and isolated Scottish waters.
  • Feeds on: Small fish and occasional crustaceans.

There is another species of electric ray in UK waters – the marbled electric ray. In terms of its UK distribution it is found in the southern North Sea and parts of the English Channel, as well as in isolated areas along the west coast of Scotland. They are mostly found around the UK in the summer as they are a species that prefers warmer waters being found in the sub-tropical and tropical seas around the Mediterranean and coasts of Africa. They are similar in shape to the electric ray although it grows to smaller sizes with females reaching a maximum of four feet in length and males around two feet, although the vast majority are around half this size.

Marbled Electric Ray Defence

A marbled electric ray bending outwards in a defensive move to hit a predator with the maximum amount of electric charge.

They are generally a dark colour with a lighter mottled or speckled pattern over their backs. Like the electric ray the marbled electric ray is a solitary creature which is only active at night. The electric ray hunts as an ambush predator, lying in wait for small fish and stunning or killing them with its electric charge. They will also use their electric charge as a defence against predators and will arch their body back in order to deliver the charge with their belly which produces the most powerful electric shock. Like the electric ray the marbled electric ray has no commercial value and is only caught by commercial vessels inadvertently in trawls. The IUCN (International Union for the Conservation of Nature) do not have enough data on numbers of marbled electric ray to make an assessment on stock levels, meaning the marbled electric ray is classed as Data Deficient.

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