New Study Finds Reef Shark Populations Declining More Globally Than Previously Known

Blacktip Reef Sharks          Photo courtesy of Enric Sala

By Julia Fine, ODP Contributing Writer

Last month, a new study published in the journal Nature showed that reef shark populations are decreasing in many regions throughout the world at much greater rates than previously thought. As CBS Los Angeles reported, this is the “most comprehensive study done on the world’s shark population.” The study found that 20% of the areas they studied — across 58 countries — had no sharks at all.  “Having dived in hundreds of places around the world, from pristine to degraded, it was no surprise that a fifth of the reefs surveyed had no sharks,” said Dr. Enric Sala, the lead author of the study, who runs National Geographic Society’s Pristine Seas Project.  One important factor in the disappearance of sharks? Climate change, which caused the shifting of food supplies. But the biggest factors are demand for shark products like fins to make soup and shark bycatch by tuna fishers.

Why This Matters: As Philip Matich, a marine biologist at Texas A&M-Galveston says, “Sharks have important roles in marine ecosystems, but disturbance can alter this role.” This, in turn, can impact the ecosystem, since as one of the top predators in the water sharks regulate prey populations. But, as the study notes, not all hope is lost. Countries like the Bahamas which provide sanctuaries and protect coral reefs have healthy shark populations. This Shark Week, we should take steps to protect sharks and the coral reefs they depend upon.  As Sala says, you can sell a live shark to tourists over and over, but you “can only sell a dead shark once.”

Moving Forward

So what do these steps look like? As Chris Lowe, director of the Cal State Long Beach Shark Lab, told CBS Los Angeles, “There are tools that work, like green protected areas we know can work. Banning the use of gillnets in certain areas, we know can work. Regulating fisheries and managing them better, we know can work.”

Some parts of the US have actually implemented these steps. As Lowe continues, “California has done a really good job, I think, of managing many of its fisheries. We’ve seen shark populations decline back in the 60s through the mid-90s and then through a series of better fisheries management practices, we’ve been able to better protect many of the populations that were being harvested.”

The Meaning of More Sharks

Some fear that more sharks could potentially mean more shark attacks. However, as Lowe’s lab showed, that isn’t necessarily correct. Based on drone footage recorded during a two-year project, Lowe and his team found that “sharks simply ignore people.” He said to USA Today, “Every once in a while [the sharks] change their path, they get a little startled and take off.” Last year, there were only 64 documented unprovoked shark attacks worldwide, and only two were fatal.

To Go Deeper: Read the article on the global status of reef sharks and the National Geographic story on it.

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