Shark Saver

Rows of sharp teeth, a keen sense of smell, and a sleek, powerful body help make sharks top ocean predators. In fact, it might seem like nothing could pose a threat to these superior hunters. But many shark species are at risk of dying out.

One of the main reasons is fishing. Some fishers intentionally catch sharks for food. In other cases, the animals are caught by accident in nets and traps intended for other fish species—a phenomenon called incidental catch. Even when fishers release these sharks alive, large numbers die afterward due to the stress of being captured.

Sharks have rows of sharp teeth, a keen sense of smell, and sleek, powerful bodies. All of this helps make them top ocean predators. It might seem like nothing could threaten these superior hunters. But many shark species are at risk of dying out.

One of the main reasons is fishing. Some fishers catch sharks on purpose for food. Others set nets and traps for other fish species, but they catch sharks by accident. This is called incidental catch. Fishers may release these sharks alive. But large numbers die afterward because of stress from being captured.

Scientists say urgent action is needed to protect these magnificent ocean animals. That’s prompted many countries to enact laws limiting shark fishing. However, tens of millions of sharks continue to die after being caught by accident. So researchers are looking for innovative ways to keep sharks out of fishers’ gear.

One team of scientists in Australia investigated a simple modification to fishing traps. They found that it reduced the number of sharks accidentally caught in the traps while boosting the catch of other fish. That’s a win-win for both conservation efforts and fishers.

Scientists say quick action is needed to protect these magnificent ocean animals. That’s why many countries have passed laws to limit shark fishing. But tens of millions of sharks still die after being caught by accident. So researchers are looking for new ways to keep sharks out of fishers’ gear.

One team of scientists in Australia did a study. It involved a simple change to fishing traps. They found that this reduced the number of sharks accidentally caught in the traps. It also increased the catch of other fish. That’s a win-win for both conservation efforts and fishers.

Sharks have been swimming Earth’s seas for some 420 million years, since long before the age of the dinosaurs. In that time, sharks have persisted through at least five mass extinctions—events that wiped out more than 70 percent of all species on the planet.

But even these hardy survivors struggle in the face of intense fishing. A team of scientists recently looked at declines in the populations of 1,199 species of sharks and their close relatives, rays and chimeras. The team gathered data from the fishing industry, government reports, and scientific surveys. Based on that information, the group estimated that about one-third of shark species are threatened with extinction (see Sharks At Risk). Three species that haven’t been seen in many years may already be extinct.

Sharks have been swimming Earth’s seas for some 420 million years. They were here long before the dinosaurs. Sharks have survived through at least five mass extinctions. Each of these events wiped out more than 70 percent of all species on the planet. 

But even these hardy survivors struggle because of intense fishing. Recently, a team of scientists studied sharks and their close relatives, rays and chimeras. The team looked at population declines of 1,199 species. They gathered data from the fishing industry, government reports, and scientific surveys. Based on that information, the group made an estimate. About one-third of shark species are threatened with extinction (see Sharks At Risk). Three species haven’t been seen in many years. They may already be extinct.

The common threat facing all sharks is overfishing. This happens when fishers remove animals from the ocean faster than their populations can be replaced through reproduction. “We cannot directly see the emptying of the world’s oceans over the past century,” says Nick Dulvy, a marine ecologist at Simon Fraser University in Canada and the study’s lead author. “All we see is full supermarket fish counters. It’s only when we look at the data that we see evidence that many formerly abundant species are now severely depleted.”

The common threat facing all sharks is overfishing. This happens when fishers remove too many animals from the ocean. The animals can’t reproduce fast enough to replace their populations. “We cannot directly see the emptying of the world’s oceans over the past century,” says Nick Dulvy. He’s a marine ecologist at Simon Fraser University in Canada, and he led the study. “All we see is full supermarket fish counters. It’s only when we look at the data that we see evidence that many formerly abundant species are now severely depleted.”

Sharks are vital to their ocean ecosystems—communities of organisms interacting with their physical environment. Many are apex predators with few natural enemies. In this role, sharks help keep other species in balance. Their disappearance has serious consequences for marine ecosystems.

When it comes to saving sharks, fishing regulations can make a difference. In regions where rules limiting their capture have been put in place, populations of a few declining shark species have begun to rebound. But for many species, stronger protections and better enforcement of existing rules are needed. And fishers accidentally catching sharks remains a big problem.

Sharks are vital to their ocean ecosystems. These are communities of organisms along with their physical environment. Many sharks are apex predators. They have few natural enemies. In this role, sharks help keep other species in balance. Their disappearance has serious effects on marine ecosystems.

Fishing laws can make a difference in saving sharks. Some areas have passed rules to limit their capture. In those places, populations of a few declining shark species have begun to come back. But many species need stronger protections. They also need better enforcement of existing rules. And the accidental catching of sharks is still a big problem.

In 2017, a group of local fishers approached ecologist Vincent Raoult of the University of Newcastle in Australia, asking for help keeping sharks out of their traps. The traps are cages with funnel-shaped entrances. Fishers put bait inside, drop the traps from a boat, and let the traps sink to the bottom of the ocean. Fish swim in through the larger end of a funnel but have a hard time getting out through the smaller end. Unfortunately, the fishers found they were catching a lot of sharks in the traps too.

In 2017, a group of local fishers approached Vincent Raoult. He’s an ecologist at the University of Newcastle in Australia. They asked for help keeping sharks out of their traps. The traps are cages with funnel-shaped entrances. Fishers put bait inside and drop the traps from a boat. The traps sink to the bottom of the ocean. Fish swim in through the larger end of a funnel. But they have a hard time getting out through the smaller end. Sadly, the traps were catching a lot of sharks too.

Raoult and his colleagues decided to test whether magnets could help keep sharks out of the traps. Sharks have sensory organs in their snouts that sense electromagnetic fields. The organs may help sharks detect prey, says Raoult, because animal muscle movements rely on electrical signals. Magnets can create a much stronger magnetic field than a swimming fish. The team’s hypothesis was that magnets might overstimulate sharks’ sensory organs and repel the animals away from traps. For a shark, Raoult explains, the experience might be “like a really bad smell—it doesn’t hurt, but it’s very unpleasant.”

Raoult and his collaborators tested the idea on 1,015 traps divided into three groups. For the first batch, they glued four 10 centimeter (4 inch) magnets around each trap’s entrances (see Trap Test). For the second batch, they attached non-magnetic metal pieces the same size and shape as the magnets. That would tell the scientists whether sharks were responding to the metal’s appearance or to magnetic effects. The third batch was left unchanged. These last two groups served as controls to compare against the magnet group.

Raoult and his team decided to conduct a test. They would see if magnets could help keep sharks out of the traps. Sharks have sensory organs in their snouts. These organs sense electromagnetic fields. Animal muscle movements rely on electrical signals. So the sensory organs may help sharks detect prey, says Raoult. Magnets can create a much stronger magnetic field than a swimming fish. The team’s hypothesis was that magnets might overload sharks’ sensory organs. That could drive the animals away from traps. Raoult says that, for a shark, the experience might be “like a really bad smell—it doesn’t hurt, but it’s very unpleasant.”

Raoult and his team tested the idea on 1,015 traps. They divided the traps into three groups. For the first batch, they glued four magnets around each trap’s entrances (see Trap Test). Each magnet measured 10 centimeters (4 inches). For the second batch, they attached non-magnetic metal pieces. These were the same size and shape as the magnets. That would show whether sharks were responding to the metal’s appearance or to magnetic effects. They didn’t change the third batch. These last two groups were controls to compare against the magnet group.

After several months of testing, the results were in: Traps with magnets caught 30 percent fewer sharks. They also caught 30 percent more fish—probably because a shark in a trap scares away other fish. Raoult hopes trap fishers around the world adopt this simple modification, which costs just $10 per trap. “Any fisher can put magnets around their funnel entrances and see a reduction in the number of sharks they catch,” he says.

Magnets alone can’t solve the issue of unintentional shark catch. They don’t seem to work as well on other types of fishing gear, like hooks. But different equipment modifications show promise: For example, fishing hooks with an altered shape may give sharks a better chance of survival after release. And some types of fishing line may be easier for sharks to bite through so they can free themselves. Every little bit helps, says Raoult: “Anything we can do to reduce the accidental catch of sharks is going to have good conservation benefits.”

The test lasted for several months. Then the results were in. Traps with magnets caught 30 percent fewer sharks. They also caught 30 percent more fish. That’s probably because a shark in a trap scares away other fish. Raoult hopes trap fishers around the world make this simple change. It costs just $10 per trap. “Any fisher can put magnets around their funnel entrances and see a reduction in the number of sharks they catch,” he says.

Magnets alone can’t solve the problem of accidental shark catch. They don’t seem to work as well on other fishing gear, like hooks. But different changes to equipment show promise. For example, the shape of fishing hooks can be altered. That may give sharks a better chance to survive after release. And some types of fishing line may be easier for sharks to bite through. Then they can free themselves. Every little bit helps, says Raoult. “Anything we can do to reduce the accidental catch of sharks is going to have good conservation benefits.”