The great predator, a friend of ecological balance: as shark populations decrease and their habitats become more threatened, mankind plays a critical role in the survival of these ancient marine creatures.

• Author: Balaguer, Alejandro

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In a place where silence reigns, in the ocean depths surrounding Costa Rica's remote Isla del Coco, a group of voracious predators exercises control over the food chain. They are hundreds of whitetip sharks and hammerheads, surrounded by schools of "cleaner fish" and eagle rays, as well as immense tiger sharks, feasting on the multitude of big fish available in this well-stocked underwater fish market.

Known as a living laboratory for the study of fish migration, Isla del Coco--also called Isla de los Tiburones (Island of the Sharks)--is part of a system known as the Eastern Tropical Pacific marine conservation corridor that joins the islands of the region

A half dozen or more giant and intimidating tiger sharks--no longer abundant in the world's oceans--swim in circles around my kayak, as if to confirm the presence of possible food. They accompany me on my journey through these untamed coastal areas surrounding the ten square miles of primary forests and spectacular waterfalls that give life to this green patch of land amid the great blue.

Fortunately, the tiger sharks decide to go after a big school of horse mackerels, and I find myself drifting along with the current in the company of the underwater photographers from the Albatross Media Foundation. They have just finished a dive near Manuelita, a neighboring islet famous for being one of the sharks' cleaning stations. Kevan Mantel, a British professional diver who is filming the behavior of sharks in the depths around Manuelita explains more about this surprising, productive, and exceptional site. "The great predators come here to find food, but also to find 'cleaner fish' that eliminate parasites and other stowaway organisms that attach to their skin." Like all living creatures, sharks are part of a complex food chain. The parasites of the shark are a good snack for the abundant butterflyfish and the king angelfish. Mantel prepares his underwater camera for another dive and disappears below the waters with other members of the expedition.

The tiger sharks are persistent stalkers and they are keeping me company again. I can see that ocean treasures are not just a thing of legends and that the name "Island of the Sharks" is well deserved. The photographers, now 98 feet deep, are documenting this with their cameras. But the abundance of sharks we are seeing today around Isla del Coco is actually not so common. In fact, the situation is rather bleak for shark populations around the world. Currently the estimate is that. between 50 and 100 million sharks are lost to fishing every, year, and many specialists believe that future studies will show that these numbers have been significantly underestimated. If you keep in mind that, approximately 90 percent of the population of the big commercial species has already been wiped out, this is a marine holocaust.

Sharks--magnificent beings that have inhabited the oceans for more titan 400 million years (since even before the existence of dinosaurs)--are disappearing much more quickly than previously thought. And if they were to go extinct,, ocean systems could collapse.

As predators, sharks have evolved to play an important role in controlling the populations of their prey, especially those in the upper echelons of the food chain. These, in turn, have a huge influence on regulating the level of other species.

After my visit to Isla del Coco, I take a trip to Javeriana University in Bogota where a unique event is taking place. Experts from all over Latin America have gathered to share...