By Rodolfo Chisleanschi Translated by Maxwell Radwin
- Half of the shark species that inhabit the southwest Atlantic are threatened with extinction, due mostly to sport fishing and bycatch.
- In Argentina, a campaign is underway to get sport fishers to tag and release any sharks they catch.
- The campaign, as well as a ban on the killing of captured sharks, is helping address the problem.
San Blas, the southernmost point of Buenos Aires province, is the heart of sport fishing in Argentina. The physical characteristics of the seafloor, with channels and estuaries that host many species of fish, make it a massive attraction for any lover of rods and nets.
In the 1990s, when the slaughtering of sharks was still permitted in sport fishing, thousands of sharks died at the hands of fishers. A doctoral thesis by Luis Lucífora, published in 2003, backed up what was happening in San Blas with hard numbers. “He found that every boat took up to 18 sharks per trip. It was a massacre, more than 3,000 sharks per season,” said David Dau, a fisherman who, back then, would kill every shark he caught.
From that moment on, without any support and using his experience fishing for trout, dorado and surubí, which involves the practice of returning fish back to the water, Dau decided to take on a colossal task: “I set out to change fishermen’s perspective. Sharks are a beautiful fish, perfect; why do they have to die?” he asked.
Today, some 150 sport fishers participate in a project called Conserving Sharks in Argentina, which helps install small plastic devices in the dorsal fins of captured sharks. The devices have identification numbers that allow researchers to collect information about sharks’ migratory behavior and to develop better conservation strategies for them.
Eleven species threatened with extinction
The southwestern part of the Atlantic Ocean, known as the ASO and comprising the waters off Brazil, Uruguay and Argentina, are home to 57 species of rays, sharks and roosterfish, cartilaginous fish characterized by their lack of bone structure. Twenty-two of them are sharks and more than half face some degree of threat of extinction. The sand tiger shark (Carcharias taurus), the school shark (Galeorhinus galeus), the broadnose sevengill shark (Notorynchus cepedianus), the copper shark (Carcharhinus brachyurus) and the narrownose smooth-hound (Mustelus schmitti) are among the most threatened species.
“The sand tiger shark’s case is to me the most drastic,” said Juan Martín Cuevas, a biologist and consultant with the Wildlife Conservation Society (WCS) in Argentina. Known as the sarda and mangona in Uruguay and Brazil, respectively, the species is also found in coastal waters around the world, but is critically endangered. A report from a WCS Argentina trinational workshop in 2020, attended by public and civil society organizations from Brazil, Uruguay and Argentina, identified a population decrease of around 82% in Argentina and up to 90% in Brazil. On average, it’s estimated that the number of sand tiger sharks in the ASO is 70% less than it was 50 years ago.
“Artisanal and sport fishing between 1980 and 2000 is directly related to these figures,” Cuevas said. The high rate of incidental capture, or bycatch, by industrial boats fishing for other species has also contributed to the decline.
The physical and biological characteristics of the species make for an explosive mixture that threatens its survival on several fronts. Sand tiger sharks are large — longer than 3 meters (10 feet) for females and 2.75 m (9 ft) for males, and weighing up to 100 kilograms (220 pounds) — making them very attractive for afficionados of so-called “heavy fishing.” But they also reach sexual maturity relatively slowly, with the females beginning to produce at 8 years old and only giving birth to two offspring at a time.
Another factor that exacerbates the situation for sand tiger sharks is that, unlike other sharks that chew their food, they gobble it all down in one bite. “Because of that, the hook is often swallowed and ends up stuck in different parts of the animal’s digestive tract,” Dau said. “In its attempt to escape, the hook tears the stomach tissue, throat and tongue, resulting in its death.”
In July 2021, following from the trinational workshop and in an effort to stave off the shark’s possible extinction, experts and officials came up with a strategic plan for sand tiger shark conservation in the ASO region. “We prepared a regional agenda in which we define priorities and 16 objectives and 44 actions with the idea of implementing them over the next 10 years,” Cuevas said.
The sand tiger shark isn’t the only one in danger
All species of shark, despite being the top predators in the sea, are in danger. “We’re eating them,” Cuevas said. “About 100 million individuals are pulled from the water every year.”
For the last 20 years, biologist Julieta Jáñez has worked with the Teimakén Foundation, where various projects are underway to study the broadnose sevengill shark, categorized globally as vulnerable. “One of [the projects] aims to identify where it reproduces, because that information will help manage the species’ conservation,” she said. “We know, for example, that we can find juveniles or newborns in the Verde and Falsa bays, in Buenos Aires province, in November. So during that time, we shouldn’t allow fishing.”
Biologist Andrés Jaureguizar, an adjunct researcher with the Argentine Institute of Oceanography and a collaborator on field studies carried out by the Temaikén Foundation, provided a broader view of the situation: “We think that the entire provincial coast is a breeding area because we find small specimens in the Mar del Plata, Monte Hermoso, Bahía San Blas and southern Uruguay.” The Valdés Peninsula, some 750 kilometers (470 miles) further south, could be an intermediate zone, either for mating or feeding.
Although their situation isn’t as critical as other sharks, such as the sand tiger shark, the dogfish or narrownose smooth-hound, the situation for the broadnose sevengill shark is also concerning. “It’s true that the females can give birth to 60 offspring (although most figures tend to be closer to 30), but they tend to do it in areas where there is a lot of artisanal fishing and so their survival depends on the fate of some juveniles that are born just 50 centimeters [20 inches] long. The mortality rate is very high,” Jaureguizar said.
The issue of reproduction rates and breeding areas is a crucial part of the puzzle for researchers. “Each species has different reproductive strategies: the narrownose smooth-hound breeds every year; the broadnose sevengill shark, copper shark and sand tiger shark, every two years; and recently in California they discovered that the school shark has a tri-annual cycle,” Cuevas said.
Migratory behaviors are the other big question mark. They’re very difficult to manage in the ASO due to a chronic lack of resources needed for long-term studies of groups traveling long distances. In the case of cartilaginous fish, satellite monitoring is expensive and often ineffective, as the species don’t need to surface to breathe.
A project connecting fishers and scientists
The citizen science project Conserving Sharks in Argentina, launched 10 years ago, is showing its first results. The idea is that every time a sport fisher catches a shark, they tag it with a plastic device with an identification number before returning it to the water. That way, the next time the shark is caught, scientists can collect data on its migratory patterns.
To date, the 150 fishers participating in the project have managed to tag more than 800 sharks. “Thanks to our work, we’ve been able to identify areas with copper sharks in their first years of life, in the Faro Querandí [in Buenos Aires province] and form a hypothesis about their migration from there to La Paloma, Uruguay, where they were caught by artisanal fishermen,” Cuevas said.
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One high-profile case is that of a 2-m (6-ft) adult female copper shark caught in December 2018 in the Mar de Plata. It was recaptured 297 days later in Espíritu Santo, Brazil, more than 2,500 km (1,600 miles) away. “This is a route headed north that was previously unknown to the species,” Cuevas said.
The tagging idea has also been attempted in Uruguay, “but it didn’t work,” said Andrés Milessi, a biologist with the Cetacean Conservation Organization and promoter of the country’s Healthy Oceans (“Océanosanos”) campaign. “What’s more, we recently learned of a kayak fishing trip that was a true massacre. We need to work with people, raise awareness, educate,” he said.
Environmental education is seen as the most successful tool in the fight to reduce the mortality of sharks in southeast Atlantic waters. For that, David Dau has played a fundamental role. “It was something that I don’t understand why it happened to me, but the truth is that I started to feel something strange in the moment of killing sharks that we caught. That was in 2000, when I was around 30.”
“My area of activity was always Santa Clara del Mara, which is to say the open sea, where it isn’t easy to find sharks, and where at most I could catch eight or 10 fish per season,” he said. “But I started to notice that, year after year, that amount was going down. I knew what was happening at that time in San Blas Bay, and without being a biologist or studying the topic, I connected one thing to another and one day said, this is what it’s come to. I give away or sell my equipment or I don’t fish for sharks anymore.”
The man who changed the paradigm
Convincing fishers to stop killing sharks was almost became an obsession for Dau. His articles in magazines, appearances on TV and talks given at fishing clubs complemented the scientific studies being done to better understand sharks and develop risk-free techniques for extracting hooks from sharks’ powerful mouths. “At first, the pushback I got was terrible,” Dau said. “People thought I was crazy. They wanted the photo of them standing next to the animal hanging from its tail, or laid across their pickup truck, and they wanted to put the jaws in their living room. My colleagues wanted to kill me because I was endangering their business.”
Eventually, his fighting and preaching made some headway. “One day, the Buenos Aires Ministry of Agrarian Affairs called me. They asked if I could help them develop regulations for deep-sea sport fishing,” he said. “My idea was to convince the fishermen. Releasing [the fish] was for the good of the species, but also of the fishermen because I understood that letting them grow up ensures that there will be fish in the future. I wanted them to do it voluntarily, but a regulation prohibiting the killing of sharks could also be worked in. So in November 2007, all that fighting finally turned into a law.”
The approach, pioneered in the Argentine portion of the ASO, has not been replicated successfully in other parts of the region, however — not in the provinces in Uruguay or in Argentina’s Patagonia, much less in Brazil. Nevertheless, advocates say the idea still has time to catch on.
How awareness spreads
Fernando Riera moved to San Blas Bay in 2014. Also a shark fisherman, albeit much younger than Dau, he fervently joined the fight that, just seven years ago, was still getting started. “I didn’t have to convert. I got started doing catch and release, but when I got here I realized the mindset was a thousand years behind,” he said. “More recently, we’ve progressed a lot. We’re achieving a kind of contagion effect with my peers, and more and more fishermen want to join the project and mark their sharks.”
Dau was the one to introduce the circle hook for fishing the critically endangered sand tiger shark. “I discovered it in the United States. It has a tip that’s bent inwards so that it doesn’t get stuck in the shark’s flesh. When the fisherman reels it in, it gets stuck in the shark’s teeth and jaw without hurting it, allowing it to be returned to the water unharmed. For now, there are very few [circular hooks] and they’re expensive, but we will have to make a greater effort because it’s one of the few things that can save the sand tiger shark.”
In Punta del Diablo, Uruguay, where there’s a long tradition of fishing for large sharks, plans are being mulled about setting up traps or cages in place of mesh gillnets used to capture sharks. “We’ve been developing a project called ‘small-scale sustainable fishing’ to eradicate those nets,” said Milessi, the biologist. “With the cages, the boats that fish in the area could even capture specimens of greater commercial value.”
Activists and researchers are also trying to highlight the economic benefits to fishers still on the fence. “Sport fishermen realized that returning the sharks to the water means that it can be fished four or five times, whereas if you kill it the first time, that’s it. You get an economic return by not killing it,” said Milessi, who advocates developing a joint plan with officials, fishers and tourism operators to tag and release sharks.
“Today, the trophy is showing the video of the release,” Dau said, “instead of showing the shark hanging from a hook. Things are changing.”
“What used to bring prestige is now shameful,” Riera added. “If someone shows off a dead shark, the social rejection is strong.”
“I have no choice but to be optimistic because the results demonstrate that when there’s some success, others rally around that,” Cuevas said. “The challenge now is not to lower expectations even for a second in the 10 years to come.”
The situation is complex, but it appears that the top predators of the southwest Atlantic have yet to take their last bite.
This article was reported by Mongabay’s Latam team and first published here on our Latam site on Dec. 3, 2021.