Sharks are “functionally extinct” from many of the world’s reefs, new global survey finds

Sharks are absent on many of the world’s coral reefs, suggesting that they are “too rare to fulfill their normal role in the ecosystem, and have become ‘functionally extinct,’” according to a new landmark study.

Conducted by Global FinPrint and published in the journal Nature, the study involved surveying 371 reefs in 58 countries. Sharks were not found on nearly 20 percent of reefs, “indicating a widespread decline that has gone undocumented on this scale until now,” Global FinPrint said in a press release.

Six nations and territories had essentially no sharks detected by the survey team, including Dominican Republic, the French West Indies, Kenya, Vietnam, the Windward Dutch Antilles, and Qatar. Altogether, just three sharks were observed among these nations collectively over the course of 800 hours.

"While Global FinPrint results exposed a tragic loss of sharks from many of the world's reefs, it also shows us signs of hope," Paul G. Allen Family Foundation Co-Founder and Chair Jody Allen said. "The data collected from the first-ever worldwide survey of sharks on coral reefs can guide meaningful, long-term conservation plans for protecting the reef sharks that remain."

Global FinPrint attributes the species losses in large part to overfishing, “with the single largest contributor being destructive fishing practices, such as the use of longlines and gillnets.”

"Although our study shows substantial negative human impacts on reef shark populations, it's clear the central problem exists in the intersection between high human population densities, destructive fishing practices, and poor governance," according to Demian Chapman, Global FinPrint co-lead and associate professor in the Department of Biological Sciences and Institute of Environment at Florida International University. "We found that robust shark populations can exist alongside people when those people have the will, the means, and a plan to take conservation action."

The study also set out to highlight regions where shark conservation has been successful, with the best-performing nations (compared to the average of their region) being Australia, the Bahamas, the Federated States of Micronesia, French Polynesia, the Maldives, and the United States. Researchers found these countries promoting healthy shark populations by being generally well-governed, and either instituting bans on shark fishing or having science-based management limiting how many sharks can be caught.

"These nations are seeing more sharks in their waters because they have demonstrated good governance on this issue," Aaron MacNeil, lead author of the Global FinPrint study and associate professor at Dalhousie University, said. "From restricting certain gear types and setting catch limits, to national-scale bans on catches and trade, we now have a clear picture of what can be done to limit catches of reef sharks throughout the tropics."

"Now that the survey is complete, we are also investigating how the loss of sharks can destabilize reef ecosystems," Global FinPrint Co-Lead and Florida International University College of Arts, Sciences, and Education Dean Mike Heithaus added. "At a time when corals are struggling to survive in a changing climate, losing reef sharks could have dire long-term consequences for entire reef systems."

Global FinPrint began collecting data for the study in 2015 using baited remote underwater video stations (BRUVS), which featured a video camera, dubbed a “Chum Cam,” placed in front of a standard amount of bait. BRUVS surveyed coral reef ecosystems in the Indo-Pacific, Pacific, the Western Atlantic, and the Western Indian Ocean regions.

The team was able to capture and analyze more than 15,000 hours of video over the four-year study period.

“The work was conducted by hundreds of scientists, researchers, and conservationists organized by a network of collaborators from Florida International University, the Australian Institute of Marine Science, Curtin University, Dalhousie University, and James Cook University,” Global FinPrint said.

Shark endangerment has been a topic of concern for Canada recently, with the Ecology Action Center calling on the country’s leadership to propose an international ban on the retention on endangered shortfin makos.

“Last year, Canada co-led a proposal to heed the voice of science and prohibit fisheries from keeping any North Atlantic shortfin mako sharks, dead or alive. We are urging Canada to show global leadership in marine conservation by again proposing this international ban," the EAC said in a 24 July press release. "Earlier this year, Canada prohibited retention of these sharks in Canadian waters. It’s time to make this ban international."

The nonprofit cited poor regulation of fishing practices as a primary driver for the decline in the North Atlantic shortfin mako shark population, which hit a critical low last year that classified the species as endangered. According to the EAC, scientists have reported that even if the reported mako catch were zero, it would take 25 years for the population to rebuild, with 50 percent odds at recovery.

“Despite the drastic situation, there is no international ban on retaining mako sharks. The International Commission for the Conservation of Atlantic Tunas (of which Canada is a member) manages fishing fleets that can make or break the mako sharks. Last year, the ICCAT failed to pass the ban,” the EAC said. “Canada has an opportunity to show global leadership again. Until 31 July, ICCAT is accepting proposals regarding management measures that will decide the fate of shortfin mako sharks. ICCAT has the power to stop their decline in the Atlantic, but a member country needs to propose a ban for this to happen. Canada should be that country.”

Photo courtesy of Andy Mann/Global FinPrint