As the first known person to dive into several coral systems in the Red Sea, Julia Spaet expected to encounter some surprises. Over several years, she sighted dolphins, rays, moray eels, sea turtles, loads of fish and the most colorful smattering of coral species she’d ever witnessed. But the most surprising thing was what she didn’t see: sharks.
Spaet, at the time a Ph.D. student in marine biology at the King Abdullah University of Science and Technology (KAUST) north of Jeddah in Saudi Arabia, was conducting a large-scale survey to estimate the number of sharks in the Red Sea. Her results suggested the answer was ... not very many. In a study published recently in the journal Biological Conservation, Spaet and her coauthors found that illegal fishing has devastated—and continues to devastate—sharks off the western Saudi coast.
“It seems like populations have declined dramatically in the past few decades,” says Spaet, who is now a post-doctoral researcher at Cambridge University. This is worrisome because, she adds, because “as top predators, sharks hold an important position in the maritime ecosystem. If they disappeared in the Red Sea—or anywhere else—this would cause unpredictable changes in this ocean basin.”
When she first arrived in Saudi Arabia, information on sharks was scarce. To figure out what was around, Spaet and team used traditional bait and hook techniques to catch live sharks, gathered genetic samples from dead sharks at the fish market, and trailed baited remote underwater videos (BRUV) behind boats watching for candid shark shots. Their research required overcoming some unique regional challenges—for instance, having to confront a boat of Yemeni pirates who had stolen their long lines one night.
But the challenges didn’t end at the ocean. They continued at the local fish market, where Spaet conducted interviews with fishermen to supplement her data.
The relatively new King Abdullah University is an oasis of relative liberalism in the desert; international students dressed in modern garb and sexes aren't segregated. But much of Spaet’s research involved going out to into a local Saudi fish market, an area traditionally dominated by men. “In the beginning, the locals were totally shocked because women just don’t go there,” she says. This was compounded by the fact that there were few tourists, so a female westerner was a rare sight, she adds.
But Spaet’s interviews allowed the researchers to document around 30 different species of sharks including hammerheads, tiger sharks, "silkies," various reef shark species and the first known record of the pigeye shark—a small, rare species in the Red Sea. Shark fins sell at premium prices, sometimes to international markets, while the rest of the meat is consumed locally.
While there is no historical population count for sharks in the Red Sea, Spaet said in a follow-up email that her research team compared their results to those of similar studies conducted in fished and unfished reefs around the world. That data didn’t give them an estimate for the overall population of sharks in the Red Sea. But it did allow them to calculate that sharks in reef systems in the Red Sea of Saudi Arabia were between 10 and 94 times lower, depending on the species and place, than estimates from places like Belize, Hawaii, Indonesia, Fiji and the Bahamas.
“This is a worrying sign that sharks in the eastern Red Sea are becoming exceptionally scarce and therefore several orders of magnitude more difficult to find,” Spaet says.
Mark Bond, a shark expert at Florida International University who was not involved in Spaet's study, says that Spaet’s work was conducted in an area without much capacity for research. “There are huge swaths of the world where we really don’t know what’s going on,” he says. He adds that Spaet's work lays important groundwork, especially the part conducted with BRUVs – a method that can be reproduced in the future to track and monitor how populations change.
One species that isn’t having trouble, however, is the whale shark. Jesse Cochran studied whale sharks in the Red Sea as a PhD student at KAUST around the same time as Spaet, and found that the giant bottom feeders are doing pretty well. In a recent study published in The Journal of Fish Biology, he and his coauthors monitored a large group of whale sharks that came together every year for unknown reasons and in related work, they tracked more than 50 of the giant fish using satellite devices. They found that many whale sharks bounce around the southern and central Red Sea, with only a few swimming into the Indian Ocean.
Whale sharks, it seems, have been spared due to their prodigious size. Growing to an average length of around 30 feet and weighing around 10 tons, these behemoths are usually too big for small boats to bring into the market and hard to fish with bait, since they eat plankton. Cochran says that only once in the seven years he was there did he hear about a fisherman bringing a whale shark in, after it became entangled in his net.
For all the other Red Sea shark species, the primary threat is fishing. Though technically illegal in Saudi waters under royal decree since 2008, Spaet says that shark fishing is still widely practiced and many fishermen don’t even know the rule exists. “The law is not doing anything at all,” she says.
In terms of shark declines, it's hard to point the finger elsewhere, she says, as the Red Sea has little pollution and next to no tourism. Spaet’s team also surveyed waters across the strait on the Sudanese side, where the locals don’t fish much for sharks. “The populations were extremely healthy and the only difference was fishing,” Spaet says, adding that the African country now has a little tourism focused around whale sharks, which also helps focus conservation attention on that species.
These shark fishing techniques are indiscriminant; a previous study in Fisheries Research that Spaet was involved in shows that fisherman target shallow nursery areas and capture hundreds of sharks. “They basically wipe out an entire generation in one day,” she says, adding that hammerheads and spot-tail shark populations have been hit particularly hard by this practice.
Many of these catches ended up in the fish market where she did surveys. Spaet says she had to step through puddles of blood mixed with the oil from cars, with sharks carcasses laid out for sale on the ground under the smoldering Saudi sun. “The smell of the fish market is unbelievable,” she says.
Bond says that evidence shows that sharks do better in protected marine areas, whether it's due to less direct harvesting of the fish or whether it means they benefit from a larger prey base in these areas. While Saudi Arabia has rules against shark fishing, it's important to start enforcing them immediately rather than five or 10 years down the road, he says.
Spaet says the laws would be relatively simple to enforce, because the Saudi coast guard already checks most boats coming and going into port. But it may be too late: she believes that several species may already be doomed. “I think [our study] shows pretty clearly that if we reduce fishing on the Saudi side, we would have the chance to recover at least some of the species.”