Overfishing, not climate change, is pushing some sharks to brink of extinction

Researchers analyzed more than 22,000 hours of video footage to study the massive decline in reef sharks. Jon Dodd, executive director of the Atlantic Shark Institute, called the study “rock-solid, not-much-to-debate.”

A Caribbean reef shark. Scientists studied more than 22,000 hours of video footage from baited underwater video systems (typically a GoPro with 1 kilogram of crushed oily fish in front of a camera) deployed at a reef. All sharks and rays observed as part of this study were identified to the lowest class, the time they appeared, and the maximum number of each species in a single frame.Andy Mann

PROVIDENCE — A newly published study about sharks living on coral reefs collected a staggering amount of video, which led to a sobering conclusion: Overfishing is pushing reef sharks to the brink of extinction.

More than 150 researchers from around the world collaborated on the five-year initiative between 2015 and 2020 led by researchers at Florida International University’s Global FinPrint project, which was founded in 2015. It is the first shark and ray survey of its kind and was funded in partnership with the Paul G. Allen Foundation.

A recent report in Science reveals that the population of five major reef shark species has decreased by 60 percent to 70 percent. Other individual shark species that could no longer be found on 34 percent to 47 percent of surveyed reefs had been listed in lower-risk extinction categories by the International Union of Conservation of Nature, a group that fights to save species from extinction.

Colin Simpfendorfer, the lead author of the study and an adjunct professor of marine and aquaculture science at James Cook University in Australia said, “These are some of the best estimates of population decline of widespread shark species because of the very large number of reefs and countries sampled. This tells us the problem for sharks on coral reefs is far worse and more widespread than anyone thought.”

The declines in the numbers of these reef sharks and over 50 other species of sharks were presented at the November 2022 Conference of the Parties of the Convention on the International Trade in Endangered Species of Wild Fauna and Flora. This will aid governments in regulating their trade.

Grey reef sharks at the Northern Great Barrier Reef in Australia. Scientists studied more than 22,000 hours of video footage from baited underwater video systems (typically a GoPro with 1 kilogram of crushed oily fish in front of a camera) deployed at a reef. All sharks and rays observed were identified to the lowest class, the time they appeared, and the maximum number of each species in a single frame.Andy Mann

The study’s contributing scientists said that human and environmental factors are affecting shark species and disrupting the ecosystem.

According to the study, areas with marine protected areas, which are located more frequently in the waters of wealthy nations, had increased reef shark populations, while less wealthy nations with weak conservation measures had depleted reef shark populations. Countries with lower shark populations had a high potential for repopulation if they became shark sanctuaries, or invested in shark fisheries management.

“While overfishing and poor governance is associated with the absence of these species, they are still common in Marine Protected Areas and places where shark fishing was banned or highly regulated,” said Demian Chapman, lead scientist of Global FinPrint and director of the Sharks and Rays Conservation Program at Mote Marine Laboratory. “Reef sharks can be important for human livelihoods through dive tourism, and if fished very carefully. An investment in reef shark conservation can therefore be good for people, too.”

In Australia, meat from a number of threatened or endangered sharks is being served as fish and chips, according to the University of Adelaide. Researchers analyzed the DNA of fillets from more than 100 retailers across Adelaide and areas of South Australia to determine what type of fish was being sold.

Peru is the leading exporter of shark fins worldwide, despite the United States banning the trade on World Oceans Day in 2021. The South American nation has tripled its exports of shark fins both legally and illegally sourced, according to Oceana, a nonprofit working to change policies and restore the world’s oceans.

Demand for shark fins has led to overfishing and cruel fishing practices, where sharks are tossed back into the ocean and die, according to Oceana. More than 73 million sharks end up in the market every year, the group says.

In Asia, shark fin soup can cost $200 a bowl, Reuters reports.

A Caribbean reef shark. Scientists studied more than 22,000 hours of video footage from baited underwater video systems (typically a GoPro with 1 kilogram of crushed oily fish in front of a camera) deployed at a reef. All sharks and rays observed were identified to the lowest class, the time they appeared, and the maximum number of each species in a single frame. Andy Mann

Researchers studied over 22,000 hours of video to identify different species of sharks, rays, and other coral inhabitants. They recorded each shark sighting, counted species, and avoided duplicate data.

Baited underwater video systems built with a GoPro camera and filled with crushed oily fish were dropped at reefs in up to 40 feet of water for no less than an hour. Date, depth, time of placement and retrieval, location, and sea and weather conditions were recorded.

Jon Dodd, executive director of the Atlantic Shark Institute in South Kingstown, said his organization uses the same video systems to monitor white sharks in New England waters. He called the colossal reef study “rock-solid, not-much-to-debate” research, and a “monumental undertaking” that would impact all shark research.

Grey reef sharks in New Caledonia. Andy Mann

The United States boasts one of the best-managed and sustainable shark fisheries in the world, but still has declining shark numbers, according to Dodd.

NOAA Fisheries said that none of the 43 Atlantic shark species they manage are endangered in US waters under the Endangered Species Act. Two of the shark species are listed as threatened: the scalloped hammerhead populations in the Caribbean and off the coast of South America, and the oceanic whitetip population globally.

Dodd says it’s easy to overlook the steadily declining numbers of Atlantic sharks when they aren’t listed on the endangered species list.

“While on the surface it may sound good or reasonable that none of the sharks are considered endangered [in US waters], many of these sharks, their populations are decreasing,” Dodd said. “They are getting to levels that are going to be very difficult to come back from in our lifetime.”

The shortfin mako is one of those Atlantic sharks not listed as endangered in the US, but according to the International Union of Conservation of Nature, it is endangered worldwide.

The Atlantic Shark Institute monitors great white, mako, thresher, porbeagle, blue, spinner, and blacktip. All of them have declined in recent years, Dodd told the Globe.

“It’s difficult to feel good or to feel we accomplished something because it is local,” Dodd said. “None of these sharks have roads to stay on; they don’t run into state or country boundaries. The appearance of sharks in State A or Country A doesn’t mean they are healthy.”

Dodd said as sea temperatures have risen, the range of sharks in New England waters is drastically changing.

“Sharks typically move north because that’s where cooler water is,” Dodd said. “Sharks that weren’t here before have started to come out. For the first time in the last three or four years, we started to catch blacktip sharks, and now we have a project for spinner sharks.”

Warmer ocean waters are having an impact on marine-protected areas, which NOAA Fisheries use for shark management, Dodd says.

Using the NOAA ERSSTv5 monthly SST dataset (https://t.co/wRVKpB8MNv), here are the monthly averages for the North Atlantic from 1854-2023. The June 2023 value is projected based on the first 25 days of the month. Past years are shown in red, lightest=oldest, darkest=newest. [1/2] pic.twitter.com/HUwtMc6RqM

— Brian McNoldy (@BMcNoldy) June 26, 2023

Dodd said that marine protected areas are still subject to changes in a shark’s habitat, which drastically changes with rising sea temperatures. He told the Globe last year that since the 1980s, the northern edge of the high-catch density line for tiger sharks — the area where sharks can be caught in abundance — has moved northward by 250 miles. Fishermen have been catching yellowfin tuna 25 miles offshore — that’s about 75 miles closer than in previous years.

A marine-protected area that was full of sharks one season could be gone the next.

“When tiger sharks migrate 300 miles north of those areas and give birth, what happens then?” Dodd said. “Are those protected areas or not? It’s one of the reasons we do this research. What we knew 10 years ago might not be the case now.”

Dodd said that a report from the University of Maine’s Climate Change Institute indicates that the Gulf of Maine is warming faster than 99 percent of the world’s oceans. New England has the fastest increasing water temperatures in the US, up 3 degrees in the last 120 years. This is leading sharks further north, and bringing Caribbean sharks not commonly found in the Northeast to our shores.

Shark populations are slow to replenish because sharks don’t reach maturity for close to 30 years, according to NOAA Fisheries. Sharks born today won’t be ready for pups until approximately 2053.

A Caribbean reef shark. Andy Mann

Simpfendorfer urges trade sanctions on countries that don’t act to stop overfishing of threatened species of sharks.

“This means no trade should come from nations where the take of the species will threaten its survival,” he said. “This study can be used to help identify those nations where such catches would be detrimental. We need to act now to stop the widespread extinction of shark species in many parts of the world.”

The study said that bans are effective approaches in a few places, but are less likely to be adopted or effective in areas where there is an established shark fishing industry, “or if many shark fishers would lose their livelihood if a ban were implemented.”

Scientists who conducted the study offered recommendations such as adopting catch limits or placing restrictions on shark fishing gear like gillnets and longlines.