A recent study published in the Proceedings of the National Academy of Sciences found that sharks populations are disappearing in waters where humans are fishing.
The study, conducted by Conservation International Senior Director, Global Fisheries and Aquaculture Program Jack Kittinger, Ph.D. and 36 scientists, assessed about 1,800 tropical coral reefs and found that sharks and other reef predators, such as large snappers, were present in just 28 percent of the scientists’ observations. Also, they were hardly seen at all at reefs where human pressure, through fishing or pollution, was high.
“Coral reefs are in a trade war and the conservationists’ solution of choice is Marine Protected Areas,” Kittinger said via press release. “This research tells us that the closer a reef is to a major market, the more we have to temper our expectations about conservation gains, and the more important remote protected areas become for populations of top predators.”
The study showed that the number of top predators in large remote marine reserves in areas with very low human pressures is much higher – more than quadruple the numbers found in remote lightly fished unprotected areas.
Researchers used a new way of measuring the human pressures, such as fishing and pollution, to study the effects these are having on fish on the world’s reefs. The ‘human gravity’ scale calculates factors such as human population size, distance to reefs, and the transport infrastructure on land – which can determine reefs’ accessibility to fishermen and markets.
Where human pressure was high, the probability of encountering a top predator dropped to almost zero (less than 0.005). This scarcity is regardless of whether there are protections in place, such as ‘no-take’ marine reserves or restrictions on fishing equipment. Scientists believe the size of reserves in heavily fished areas are likely to be too small to protect sharks as they have large hunting ranges that likely expose them to fishing when they stray outside reserves.