The researchers found thatSharks are "functionally extinct" in 20% of the reefs.This means that the shark population isreduces to the point that it does not play an important role in the ecosystem. Or that the breeding population is so small that it can no longer be maintained.
A study conducted in 58 countries identified that in 34 of them the number of specimens corresponds to half that expected by the researchers. On some reefs, the absence of sharks was almost complete.
The main reason for the decline of sharks is thedestructive and unsustainable fishing. An estimated 100 million are killed each year for thefin and meat extraction.
The worst ranked countries for reef sharks are Qatar, the Dominican Republic, Colombia, Sri Lanka and the US territory of Guam.
With the exception of the Bahamas and the Great Barrier Reef in Australia, the shark population remains relatively high there, according to the study. Commercial fishing is prohibited in these places and the sanctuaries are well managed.
How to reverse the situation for sharks
Thesharks play a vital role to maintain the ocean ecosystem and experts say it is possible to change this.
There are two ways to reverse this situation. One isfisheries management, which extracts sustainable benefits from renewable ocean resources.
The other is thehunting ban and trade with them around the world, which would be more fair and effective to protect these animals.
The study in question was published in the scientific journal Nature and also published on the BBC News website.
By Eliane A. Oliveira. Article in Portuguese