Weipa, a small coastal mining town in Queensland, Australia, has become a haven for sports fishermen due to its annual competition, the Weipa Fishing Classic. However, in recent years, a peculiar phenomenon has been occurring. Local bull sharks have been launching audacious underwater raids, waiting for the perfect moment to snatch fish off the line. Some fishermen estimate losing up to 70 percent of their catch to these sharks, which seem to have a particular affinity for fishing boats.
(Some spoilers for the documentary below the gallery.)
This behavior is highly unusual for bull sharks and raises an intriguing question: are these often-misunderstood creatures more intelligent than we previously thought? Shark biologists Johan Gustafson and Mariel Familiar Lopez embarked on a mission to find answers. Their groundbreaking field work has been captured in the documentary Bull Shark Bandits, part of National Geographic’s 2023 SHARKFEST programming. SHARKFEST promises four weeks of thrilling and educational shark content, showcasing the captivating science, power, and beauty of these magnificent animals.
Further Reading
Camo Sharks documents the hunt for evidence of color-changing behavior in great white sharks.
This fish-stealing behavior, known as depredation, is a response to the declining fish stocks in Australia, which have decreased by over 30 percent in the past decade. The sharks have adapted and are now teaching this behavior to their fellow sharks.
“Shark depredation is occurring all over Australia at the moment,” explains Gustafson. “Many different species, including dolphins and orcas, exhibit this behavior. However, in areas with higher fishing pressure, the habituation occurs more frequently and intensively. They learn from each other and spread it throughout the population.”
Bull sharks (Carcharhinus leucas) can be found in warm, shallow coastal waters and freshwater rivers worldwide. While not true freshwater species, female bull sharks typically give birth to their pups in upriver nurseries for added protection. These sharks can grow to an average length of seven to eight feet and possess a powerful bite that can generate up to 1330 pounds of force.
Dr. Mariel Familiar Lopez with the Weipa shoreline in the background
National Geographic
Dr. Johan Gustafson prepares to tag a bull shark.
National Geographic
Lopez and Gustafson explore the underwater world with an underwater camera.
National Geographic
Gustafson holds a bull shark while Lopez prepares to measure it.
National Geographic
Bull sharks are fascinating creatures known for their opportunistic feeding habits. They eat in short bursts and can digest their meals for longer periods during times of scarcity. Their diet consists of bony fish, smaller sharks (including their own kind), turtles, birds, dolphins, and crustaceans. These territorial and solitary hunters prefer to hunt alone or occasionally in pairs.
Unfortunately, bull sharks have gained a reputation for aggression due to media reports of shark attacks. However, it’s important to note that not all bull sharks are aggressive. Just like humans and dogs, they have different personalities. While their main focus is catching meals, they don’t necessarily attack everything they see,” explains Lopez, a shark expert from National Geographic.
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To verify anecdotal reports of bull sharks stealing fish, Gustafson and Lopez embarked on a mission to capture these sharks in the act. They used a fishing line camera to capture a low-resolution shot of a bull shark stealing a hooked fish in just 20 seconds. However, they needed more footage and decided to use a 360-degree drop camera. To avoid spooking the bull sharks, they needed a noise-cancelling shark cage. Underwater cinematographer Colin Thrupp came to the rescue and constructed a unique shark cage made of polyethylene pipe. The cage absorbed sound and had a black color to reduce reflective shine. The cage served its purpose, capturing footage of six or seven bull sharks swimming together—a behavior rarely seen in this solitary species. “Part of our hypothesis is that this is a population of bull sharks that don’t really migrate that much, because they’ve got warm water conditions all year round, it’s a nice tropical area,” said Lopez. “That is maybe one of the factors [providing] opportunity for socialization. They might be getting a bit of toleration between each other because they’re getting an easy meal.”
A bull shark, captured on camera from the custom-made shark cage.
National Geographic
A bull shark swims past the custom-made shark cage.
National Geographic
Lopez prepares to take a DNA sample from a bull shark caught by the team.
National Geographic
The footage also showed a bull shark approaching the hooked fish slowly at first, waiting for it to get tired of struggling, and then biting off the fish’s tail end and propeller, before swinging back around to gulp down the rest. This is a calm, intelligent hunting strategy, per Gustafson and Lopez, the antithesis of the stereotypical mindless aggression usually associated with bull sharks. In fact, it’s strikingly similar to how killer whales—known for their intelligence—hunt, employing a surgically precise approach to save energy. “Being a top predator means you invest a lot of energy in all those catches,” said Lopez. “If that doesn’t come with a reward, you’ll have less energy for the next chase. So they have to be very intelligent [to determine] ‘Where do I put my energy in all this?’ Sometimes, when they’re not sure, they do these test bites.”
The plastic cage didn’t perform perfectly, however, starting to bounce around and buckle as swells developed and underwater turbulence increased. The communications link to the surface also went out, resulting in some tense moments until the cage was brought back to the surface. “We were in that cage and it was gloomy and the current was huge,” Gustafson recalled. “Then we saw a cable tie fly past us and thought, ‘Oh, that’s not good,’ because they’re actually what’s holding theCage [mesh] together. Then another one went by. Then the cage started to deform. It was like being in a [trash] compactor.”
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Gustafson and Lopez also managed to tag several sharks with acoustic transmitters to track their movements. Since they had spotted a juvenile shark among the adults, they also located the most likely bull shark nursery in a nearby river, taking a biopsy from one baby shark for DNA analysis. Once Thrupp had repaired and strengthened the plastic shark cage, they deployed it a second time to take biopsies of two other sharks for comparison, using harpoon-like tools.
The results showed that the juvenile they biopsied upriver was half-related to the female bull shark they biopsied back in the ocean, while the third sampled shark was related to both of them. So all three sharks likely share an ancestor between them. This is yet more evidence that the population at Weiba isn’t moving around much, because there is more opportunity for interbreeding, particularly since shark litters typically have multiple fathers, per Gustafson.
The next step includes gathering more DNA samples from the Weiba bull shark population to expand the genetic analysis, as well as tagging and tracking more bull sharks to get a sense of their movement patterns in order to determine how the top end of the gulf ecosystem (Weiba) connects to the western and eastern sides of the continent. “Do they go all the way down to Perth on the west or right down to Sydney?” said Gustafson. “Turtles tend to come back to the same beach where they were born. We think these bull sharks are starting to do the same sort of a thing. But we don’t know if they’re coming back to the same river that they were born in, or into the same area that they were born in.”
More data should also give them a better idea of the size of the bull shark population in Weiba, since the popular perception among fishermen is that there must be hundreds or thousands of them. And as fishermen keep losing their catches, there is a greater risk of more anger being directed at the bull sharks, leading to decreased support for their conservation and more calls for culling the population. (The species is listed as vulnerable on the IUCN Red List.)
“The more you spend time in the water, the probability that you will encounter a shark becomes greater,” said Lopez. “But that is just because you’re spending more time in the water fishing. It doesn’t mean there are more sharks lurking in the waters and being aggressive. It’s important to do these documentaries because you’ll never change the mind of people if you just say sharks are not bad. You need to include them in a little bit of the science, explain it. For projects like this, we go up there and spend time at the pubs talking to the fishermen. We’ve even got some fishermen helping us take samples.”
Bull Shark Bandits is now streaming on Disney+ and Hulu, premiering on NatGeo WILD on July 25, 2023.
rnrn On the Florida coast, fish are being stolen from fishermen by hungry and bold bull sharks. As the first shark species to complete what scientists have labeled a “reverse migration”, bull sharks are increasingly finding their way into shallow estuaries near human settlements, pupping grounds, and fish-filled waters.
The bull sharks’ adaptability and ability to swim from saltwater to fresh water makes them incredibly persistent—and often successful—in snatching anglers’ catches right off the hook. Hungry and relentless, they can steal a prized catch in mere seconds and often have local fishermen scratching their heads and coming up with creative—but largely ineffective—solutions to deter the sharks.
In an effort to outwit these clever fish thieves, anglers have given many methods a try, such as fishing with multiple hooks in hopes of catching their intended prey before the sharks do, using fish traps to avoid the sharks’ sharp teeth, and carrying underwater cameras to identify—and attempt to scare—the predators away. However, many anglers still find little success.
“A bull shark is basically an overly friendly, occasional hijacker anglers must deal with” says Jim Abernethy, a renown bull shark expert. In November 2015, Nat Geo Wild filmed an episode of Dr. K’s Exotic Animal ER on how Jim Abernethy actually saves sick and injured bull sharks from invasive fishing practices, only to rescue them later and release them back to where they belong.
“We do our best to keep the sharks from becoming so bold and brazen that they actually become our problem,” Abernethy says. “I can’t think of a better solution than offering respect and carrying out proper angling etiquette to keep these amazing animals wild and free while still co-existing with them.”
Though the battle between fishermen and bull sharks seems to have found no clear solution, these conservation efforts can prove fruitful and, hopefully, allow for a continued existence of both the animals and the fishermen.
