SWIMMING WITH TIGERS by Dr. "Gerald Goeden"

There is much concern about shark fishing and shark fining. Ocean conservation is at stake as predators in all the world oceans are subjected to over-fishing. Caribbean and Andaman Sea fisheries (Malaysia) are especially stressed. Growing support for eco-tourism based experiences like swimming with sharks and swimming with dolphins promise to outstrip the economic benefit of over-exploitation. The following report looks at the experience of one of our scuba divers in assessing a shark conservation project off South Africa.

During a recent photo expedition Jeff had a surprise visit from a big Tiger Shark. Jeff and Gerry tell the story:

“All of a sudden something was holding on to my scuba gear and shaking me like a feather. I was so busy getting some great shots that I didn’t see this big one come up behind me.”

“I was pretty lucky that I wasn’t hurt, but it seemed like the Tiger was just trying to figure out what I was.”

The Tiger Shark, which generally hunts at night, has a reputation for eating anything and everything and for an aggressive nature. Most of the time, Tiger Sharks eat fish, squid, seabirds, sea mammals, other sharks, and turtles.

Out of more than 360 shark species, only four have been involved in a significant number of fatal attacks on humans over the last 60-70 years: the great white, tiger, oceanic white tip, and the bull shark. Culling Tiger Sharks a few days after an attack probably has little value since most are nomadic and the offending animal may well move on. Some governments ‘protect’ swimming beaches with shark nets that catch any sharks swimming along the coast.

Even small Tiger Sharks require a lot of watching and big ones can weigh up to 1000 kg and reach 6-7.5 metres. They get the name Tiger from the vertical stripes and not from their diet. Based on diet, they are more like ‘trash-can sharks’ since stomachs have been found to contain buckets, rolls of wire, gas cans, paint brushes, and baseballs. One even contained old tires.

So why did the shark bite Jeff’s metal air tank?

First, the shark was confused by the metal on Jeff’s back. Tiger sharks have small pits (ampullae of lorenzini) on their snout and along their upper bodies which can sense weak electrical fields. Normally these sensors detect fish when the water is too murky for their usually sharp eyes to see. But different kinds of metals generate weak electric currents in seawater and alert the shark that something is going on.

Secondly, the Tiger Shark’s keen sense of smell would not be sure if the smell of human meant the next meal or danger. You don’t grow up to be a big shark without a little caution!

Finally, sharks adopt the same strategy as children; if you are unsure what something is, just put it in your mouth and taste it.

“Diving with Tiger Sharks is awesome and something I will never forget. The footage will be great for documentary work and we always learn something about these incredible animals. We have to work fast as Tiger Sharks are disappearing because of the shark fin trade and sport fishing.”

Nature has equipped these sharks with all the gear to be great hunters: they can sense movement in the dark, feel water pressure waves from injured animals, smell traces of blood in the water, and have excellent vision. They are fearless and haven’t learned to stay away from boats and fishing gear.

“Our strategy is to stay close to the bottom and keep our movements slow and steady. We have to be careful not to brush against them because their skin is like sharp sand-paper and could leave you bleeding. I will also say that paying attention to what’s coming up behind you has to go to the top of my list.”

 
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http://goedenscience.blogspot.com/
http://goedenmarineecology.blogspot.com/
http://goedenshark.blogspot.com/
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http://einsteinsnature.blogspot.com/
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