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Like something out of a horror movie

By: Guest Columnist

 | Jan 04, 2013 - 12:10 PM |
Research has shown that a piranha's bite-strength is roughly 72 pounds, or about 30 times its body weight. Supplied photo.

Research has shown that a piranha's bite-strength is roughly 72 pounds, or about 30 times its body weight. Supplied photo.

“It sure had lots of teeth,” said a 12-year-old girl about the 38-centimetre-long fish she caught in the Otonabee river near Peterborough in 1998.

Three Ministry of Natural Resources biologists didn’t know what it was and no wonder: The toothy creature was a big, but vegetarian, cousin of the much-feared piranha, a fish that would have been more at home in the Amazon River than a waterway in central Ontario.

Ten years later, a longtime fisherman in Lake St Clair, hoping to hook bluegill and bass, couldn’t believe his eyes when he caught what was probably a 4.5-pound red piranha with a mouthful of razor-sharp teeth. Red piranha have also turned up in Lakes Huron, Erie, and Ontario.

If you haven’t seen a piranha lately, find the James Bond movie “You Only Live Twice” and take a look at the villain Stavros Blofeld’s black or red-eyed piranha. You will agree that neither they, nor any of their cousins, are something we want in the Great Lakes.

The ones found there are dumped by people when the fish outgrew their home aquarium. They’re not expected to survive winter water temperatures, but who wants to take the risk?

The message is: Don’t dump fish, whatever they are, from an aquarium into a lake.

Research about the bite of Bond’s adversary’s black piranha published just a few weeks ago graphically measures the amazing strength of this small fish's powerful jaws. A biology PhD student, Stephanie Crofts, from the University of Washington, studied the bite force of these fish while in South America.

She spent her days fishing in the rivers of the Amazon basin. When a piranha was caught she held it by the tail – very carefully — and encouraged it to bite down on a specially made pressure plate that recorded the bite-strength. After leaving its mark, the fish was set free and another caught and tested in the same way.

The pressure plate showed that the average adult black piranha produces a bite of roughly 72 pounds, roughly 30 times its body weight.

Compared to many other meat-eating fish, such as the barracuda and many types of sharks, including the great white, the black piranha has the greatest bite-force-to-body-weight ratio of them all.

As a comparison, a great white shark more than six metres long can create a bite-force of roughly 4,000 pounds, but taking into account its weight, at roughly 2,500 pounds, the force created is short of twice its weight.

The piranha has evolved extremely powerful jaw muscles and large rope-like tendons that work with a very effective lever-like jaw.

Although the eating habits of the piranha might have sometimes been exaggerated, the power of their bite is now well established. Not even James Bond would want to mess with them. And that's something to remember if one of your friends is tempted to dump their aquarium piranha into a lake.

Everyone wants to hook a big one; no one wants to hook a monster.

Tanis Mercer is a student in the Laurentian University – Science North graduate program in Science Communication. Have a burning science question that can be answered in Northern Life's new science column, Talking Science? Send your question to [email protected] 

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