As much as the cinema has spent years obonating the fear of bathers towards sharks, the truth is that the greatest predator is always the human being, both inside and outside the sea. This is demonstrated once again by a new international study that has lasted five years and is now published in the prestigious journal Science.
Said investigation concludes that five of the most common shark species that live in coral reefs have decreased between 60% and 73% mainly due to overfishing. These are the gray shark, black tip, white tip, nurse and Caribbean reef shark.
These data are the result of the Global FinPrint project, in which more than 150 researchers from more than 120 institutions around the world have participated, led by Colin Simpfendorfer, from the James Cook and Tasmanian Universities (Australia), and co-directed by researchers at Florida International University (FIU).
According to the authors, overfishing has wiped out both the sharks and the prey they depend on. As shark numbers decrease, ray species on reefs increase, suggesting a shift in the major elasmobranch species in coral communities.
The researchers surveyed 391 coral reefs in 67 countries and territories, using 22,756 remote underwater video stations.
The authors conclude that shark-dominated reefs persist in wealthy, well-governed countries and in protected marine sanctuaries. In areas of poverty and limited governance, stingrays dominate reef communities.
The study, published Friday in Science, "tells us that the problem with coral reef sharks is much worse and more widespread than anyone thought," said Colin Simpfendorfer, lead author of the study and associate professor of Marine and Aquaculture Sciences at James Cook University (Australia).
Mike Heithaus, study co-author and executive dean of FIU's College of Arts, Sciences and Education, stressed that "people need healthy coral reefs."
"We are seeing that when sharks disappear, that causes other changes in these ecosystems. Keeping shark populations healthy, or recovering, is important to maintain their functions for healthy reefs," he added.
Scientists have observed that populations of shark and ray species have been lost on many reefs, and on others the ecosystem has become dominated by rays.
The exception is Marine Protected Areas (AMPs), which are aimed at the long-term conservation of marine resources.
"While overfishing and poor governance are associated with the absence of these species, they are still common in MPAs and places where shark fishing was prohibited or highly regulated," said Demian Chapman, Global FinPrint Principal Scientist and Director. Shark and Ray Conservation Program at Mote Florida Marine Laboratory.
"Reef sharks can be important to human livelihoods through dive tourism and if they are fished carefully. Therefore, an investment in reef shark conservation can also be good for people," he added. .
The first results of this study were previously used to upgrade the status of four of these species to most threatened categories on the International Union for Conservation of Nature (IUCN) Red List.
They were also presented during the most recent Conference of the Parties to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).
"This study can serve to help identify those nations where catches of these shark species would be detrimental. We need to act now to stop the widespread extinction of shark species in many parts of the world," says Simpfendorfer.
