SOURCE: The Guardian
DATE: July 22, 2020
SNIP: Destructive and unsustainable fishing has caused a crash in shark numbers across many of the world’s coral reefs, upsetting the ecological balance of the critical marine ecosystems, a major study has found.
A network of remote underwater cameras across 58 countries found sharks were “functionally extinct” at almost one in five of the 371 reefs studied over four years.
The loss of sharks was putting further pressure on coral reefs around the world that were already under threat from global heating, scientists said.
Shark numbers were lowest on 69 reefs surveyed in the Dominican Republic, the French West Indies, Kenya, Vietnam, the Windward Dutch Antilles and Qatar, where just three sharks were seen during 800 hours of footage.
The Australian Institute of Marine Science (AIMS), a partner in the research published in Nature, said the study revealed a previously undocumented global decline in sharks on reefs.
Reefs close to human populations in countries with poor governance were the worst affected.
Sharks did best in places where the use of longlines and gillnets were controlled, catch limits on sharks were in place and marine sanctuaries had been created.
Sharks play a critical role on coral reefs, keeping the balance of species across the marine habitats in check, he said. Losing sharks was impacting the health of coral reefs that many millions of people relied on for food.
Some 34 out of 58 nations had shark numbers that were half what was expected, “suggesting that loss of reef sharks is pervasive among reefs globally”, the study said.