(CN) — In a study published in Science on Thursday, a global initiative founded by researchers at Florida International University has given scientists invaluable reef data. After three years, The Global FinPrint team combed through over 20,000 hours of underwater footage across 391 reefs and found alarming losses among reef sharks and hopeful sanctuaries.
Reef sharks play a critical role in reef and ocean health. As apex predators, they eat sick and weak fish and keep various animals in good shape. They also take up habitat space and shape how other animals move and eat, so when sharks leave, corals, seagrass and even commercial fisheries start to fail.
Global FinPrint placed 22,756 remote underwater video stations in 67 nations and territories to conduct this massive survey that resulted in nearly three years of raw footage. Lead study author Colin Simpfendorfer and his colleagues found that five of the most common reef shark species have declined by 60% to 73% and are far worse off than a decade ago, despite conservation efforts. Additionally, some species weren't even found in nearly half of the reefs studied.
These dramatic losses weren't the only thing Global FinPrint found. In areas where shark numbers dropped, rays stepped up. Sharks and rays are in the same elasmobranch species category, but the Jaws stars reign regarding food chain hierarchy. The rays' newfound takeover led the researchers to believe the status quo for elasmobranches is evolving. However, the study found that ray numbers are also dropping, with ray species not detected at one-fifth of the surveyed reefs.
The researchers note that overfishing is depleting the global shark and ray populations. We have long known that sharks commonly die in fishing bycatch — getting caught in commercial fishing nets collecting smaller fish, such as mackerel. Additionally, many countries still allow shark fishing, often at the commercial level. The global shark fin trade is a $400 million industry that kills up to 100 million sharks annually.
The new estimations could place the nurse shark, Caribbean reef shark, grey reef shark, whitetip reef shark and blacktip reef shark on the IUCN Red List and gain endangered status.
However, despite these grim numbers, the Global FinPrint team found hope. In reefs in wealthy nations with strict conservation laws, such as no fishing policies and protected marine parks, sharks are in healthy numbers relative to the reefs. The study emphasizes the need for species-specific protections and claims with the right global efforts, “reef sharks can rebound in under a decade.”
The call for global action is echoed in a Science Perspective article by David Shiffman, who elaborated on the footage-processing efforts by Global FinPrint.
“The study by Simpfendorfer et al. also demonstrates the growing importance of global collaboration. Global problems require huge multidisciplinary teams because scientists or laboratories working by themselves simply cannot generate or analyze data on this scale,” Shiffman writes.
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