MARINE CREATURES THAT BITE AND STING – AND SHOCK THE TORPEDO RAY

Also known as the electric ray, this friendly creature is can be found from 1 000 metres below the surface and anywhere up into the surf zone on a sandy sea-floor where it shivers its way under the sand leaving only its gills and protuberant eyes visible. In this way it is able to ambush and stun its prey. Although beautifully marked, this ray is not particularly pretty, in spite of having a mid-brown skin marked with pale cream rosettes similar to a leopard’s spots. It’s not a very mobile creature and only moves when it is actively seeking prey, propelling itself with its tail and not with its “wings” as other rays do. They feed on smaller invertebrates and fish.

The torpedo ray belongs to the group of cartilaginous fishes. This means that, like sharks, the ray has a skeletal structure made of flexible cartilage.

Its main weapons for defense and attack are the two kidney-shaped electric organs on either side of its head. These are able to generate a static electrical charge anything from 8 to 220 volts with an amperage of up to 30 amps. Whether this current is direct (DC) or alternating (AC) depends on the species. It is ironic that these ancient creatures have used the two types of electrical current for a very, very long time, unlike mankind that only discovered these relatively recently…

Position of the two electrical organs on either side of the head. (Sketch courtesy of Wikipedia)

We often encountered torpedo rays in the surf along the Zululand coast, as well as lying well hidden in protected channels between the inshore sand-bar and the rocks along the South Ledges near Cape Vidal, as well as in some deeper rock pools. They tend to work themselves under a thin layer of sand and lie in ambush with just their eyes and gill exposed. When disturbed they swim off slowly, only to “land” once more and vanish under the sand. If one passes a hand carefully about 50mm above the creature one can feel the charge building up in the electric organs – which is as good a signal as any to leave the fish alone!

The torpedo- or electric ray (Image off the internet)

Every now and then one of us would make physical contact with one, and while the jolt it gave was unpleasant, it never had serious consequences. Those we encountered were seldom larger than about 60 cm across the “wings”, so the electrical discharge, although certainly strong enough to stun a fish, was never enough to do serious harm to a much bigger human.

So if you want to avoid a shocking experience, please take great care where you place your feet when snorkelling along the inner edge of the reefs at Sodwana Bay or Cape Vidal, or, in fact any of the many small sheltered bays along the KZN coast. There’s not much one can do to avoid one lying in the surf zone, but they are not plentiful so the chances of standing on one are pretty remote.

For more information see: https://en.wikipedia.org/wiki/Electric_ray

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