Reef shark population pushed towards extinction by overfishing, reveals study

Overfishing is driving coral reef sharks towards extinction, according to a global study released on Thursday. The study indicates a far greater peril to the marine predators than previously thought.

This is significant for humans as these shark species play a crucial role in managing their marine ecosystems. They maintain delicately balanced food webs which hundreds of millions of people rely on for sustenance.

The research, published in the journal Science, is the result of the Global FinPrint project. This project collected more than 22,000 hours of video footage from reefs across Africa, the Middle East, Asia, Australasia, and the Americas.

A team of over 100 scientists found that five of the most common coral reef shark species—gray reef, nurse, Caribbean reef, blacktip reef, and whitetip reef—have declined by 70 to 60 percent.

The depletion data was derived from a computer model that estimated what shark numbers would have been like without human pressures.

In 14 percent of reefs where sharks had been previously documented, they were entirely absent.

Colin Simpfendorfer, the lead author from James Cook University and the University of Tasmania, stated that prior to the study, coral reef sharks were not thought to be doing badly compared to their bigger cousins that dwell in deep oceans. However, the overall results of the study were quite stunning.

Ripple effects

The loss of sharks has ripple effects down the food chain. The increase in prey causes a decrease in the next level down, creating unpredictable disruptions that pose a risk to human food security.

Simpfendorfer also highlighted that reef sharks play a crucial role in keeping herbivores in check. When herbivores become more common, they consume more algae, which traps carbon for use in photosynthesis. Without sharks, carbon sequestration on coral reefs is significantly lower, impacting global warming.

‘Hope spots’

Funding for the project came from the Paul G. Allen Family Foundation, known for the Great Elephant Census. This pan-African aerial survey documented Earth’s largest land animals.

In the shark study, scientists used baited remote underwater video stations (BRUVS) to observe sharks. They surveyed 391 coral reefs in 67 nations and territories using 22,756 cameras, generating three years’ worth of raw video.

The study found that healthier shark populations were present in high-income countries with stronger regulations and greater levels of democratic participation. Lower-income countries generally had worse outcomes. However, certain “hope spots” in developing countries were also identified, such as Sipadan Island in Malaysia and Lighthouse Reef in Belize.

Co-author Michael Heithaus of Florida International University expressed hope that heavily depleted areas can be repopulated through careful management programs, as long as a source population is intact and marine protected areas are enforced.

© 2023 AFP

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