All Charged Up

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Fish were making imaginative use of electricity long before humans knew what it was.  The so called electric eel, found in South America, can generate a charge of over six hundred volts.  These eels, which can be up to eight feet long, have electric organs that account for half their body weight.  Large torpedo rays, sometimes called numb fish, are capable of producing two hundred volts.

Sharks like the Portuguese dog fish, have an electro-sensitivity which they use to help locate prey.  Although sight and smell are important tools used by sharks to zero in on unfortunate victims, electrical sensitivity is equally important.

In experiments where sharks were placed in tanks with an electrode and a piece of flounder, a fish that gives off a distinctive odour, the sharks were observed to ignore the fish and try to eat the electrodes.  In another experiment a shark placed in a tank with a live fish whose electrical activity was shielded, was observed to pay no attention to the fish.

Under sea telephone cables are sometimes attacked by sharks, who mistakenly think that supper is ready, because they detect electro magnetic emissions from cables that they think are given out by some tasty creature.

So next time Benjamin Franklin gets the credit for electricity, remember those fish were all charged up long before his time.