Throughout history humans have feared sharks.  And even in an age of computers and satellites, sharks continue to be one of the biggest mysteries of the oceans.   There are over 400 species of sharks, some on the verge of extinction, yet scientists know very little about them.  Producer Zulima Palacio spent some time with one of the few experts on sharks in the United States.  Narrated by Carol Pearson.

Wes Pratt is fishing for sharks off the Florida coast.  He uses a round hook, with an 18-meter long line, strong enough to hold a 400-kilogram animal.  The line is attached to a weight on a swivel and another line to the surface.

Wes Pratt

"The reason we use this gear," he says, "is that it makes the caught shark like a dog in a leash, so he can swim around and around in a circle and does not get tangle in other sharks."

Mr. Pratt and his team install 10 of these systems 180 meters apart and leave them for a couple of hours.  When he comes back for the sharks, it's for an entirely different purpose than what you might think.  Wes Pratt is a scientist at the Center for Shark Research at Mote Marine Laboratories in Florida.  He is conducting extensive studies on sharks, to identify them, tag them and then release them.

"By putting a tag on a shark, the tag is sort of like a 'message in a bottle' hoping that someone will catch that tag and return it," he explains.  "Each tag has a unique number that identifies that shark we tag, and a 1-800 phone number and address, so folks can phone in the tag to the MOTE headquarters."

So far, only a few hundred sharks have been tagged in the Florida Keys, and the information on shark numbers, migration and behavior is not fully understood.

"We know very little about sharks," says Mr. Pratt.  "Sharks are the lions and tigers of the sea.  They are an 'apex predator' that is an essential element of the food chain and to the local ecosystem.  The situation with sharks in the world is that populations of shark are declining, we're very concerned."

After a couple of successful taggings and several empty hooks, there's an unfortunate event. There is a local shark that had been tagged the day before.

"Oh no! What a tragedy, this is a beautiful animal," he says.  A young hammerhead swallowed the hook and died.

Hammerhead shark swallowed a hook

"The hooks we're using today are called circle hooks," he says.  "It's a hook that is designed and actually works to decrease the mortality that is always a part of fishing operations, unfortunately, it didn't work in our case."

Mr. Pratt dissects the animal and checks his stomach for any food.  "He really got it. I don't know why the hook didn't work this time," he says. "I guess they are not foolproof…He was hungry."

He takes a piece of the shark's backbone for analysis. It's one of the few ways to know a shark's age.

According to Mr. Pratt, sharks are important but vulnerable animals, partly because they take 15 to 20 years to mature.

"Sharks are valuable, vulnerable large predators," he says.  "They are one of the important brighter colors of the rainbow of life.  Their importance to ecosystem is that they are the ones that keep other species in check.  They take care of the weak, the wounded, the unfit, the aged, the sick.  They preserve the fitness of stocks of fishes by eliminating the unfit members."

Hollywood's sensational stories and their intimidating presence have made sharks objects of fear and hate.  Mr. Pratt says he is not afraid of sharks but he respects them.

"I ride a bicycle, and I have a great fear of great white automobiles," he laughs.  "People who handle cats get scratched; people who handle dogs get bitten.  I have had my finger bitten quite badly, mostly because I was holding a shark for a graduate student  - you know this was shark number 35 on a rainy night - and I ended up sticking my fingers in his mouth while I was trying to hold his head.  It was totally my fault.  It was a nasty bite, but I still have my fingers and all my toes."

Mr. Pratt's concern is that if we continue harvesting sharks at the current pace, he says, very soon we will run out of shark species.  He continues his life-long study of sharks and his attempts to change people's wrong ideas about sharks.  He says if we learn more about them and learn to appreciate their important role in the oceans, sharks will have a much better chance of survival.