One third of shark species face extinction despite fishing bans

Sharks have long been portrayed as fearsome predators, dominating the oceans with their sleek bodies and razor-sharp teeth. Movies and myths have painted them as threats to humans, but the reality is quite the opposite. Sharks have far more reason to fear us.

Nearly one-third of all shark species are now threatened with extinction, primarily due to overfishing.

This is not just a loss for sharks but a significant disruption to marine ecosystems. As apex predators, sharks play a crucial role in maintaining the balance of ocean life. Their decline can trigger chain reactions that affect fish populations and coral reefs.

A team of researchers at UC Santa Barbara recently examined whether current regulations, such as requiring fishermen to release captured sharks, are enough to protect them.

The study reveals that these mandates alone will not be sufficient. To preserve these vital creatures, a combination of strategies is necessary.

Many sharks are caught accidentally

Some sharks are specifically targeted by fisheries, but many others are caught unintentionally. This issue extends far beyond the species directly sought after by the fishing industry.

“More than half of sharks that are caught and killed in fisheries are captured incidentally and then discarded,” said Darcy Bradley, co-author of the study and adjunct faculty at the Bren School of Environmental Science & Management.

Many fisheries operate under retention bans, which require fishermen to release certain species instead of keeping them. Currently, 17 oceanic shark species are protected under these bans in tuna fisheries.

However, while these policies aim to reduce shark deaths, researchers questioned whether they truly prevent population decline. The team sought to understand the fate of sharks after they are released back into the ocean.

Shark mortality rates

To get a clearer picture of shark survival, the researchers analyzed over 150 published studies and reports on shark mortality. These studies documented the number of sharks that died either upon being hauled onto a fishing vessel or soon after being released.

The analysis covered nearly 150 different shark species, each caught using various fishing techniques. By examining this data, the team estimated mortality rates for an additional 341 species that lacked direct studies.

Certain sharks were far more vulnerable to death after capture. Small sharks and several threatened species, including thresher sharks and hammerheads, had particularly high mortality rates. Deep-sea species also fared poorly due to the extreme pressure changes they experienced when pulled from the depths.

“Mortality was surprisingly high for some species such as smoothhound sharks,” said co-lead author Leonardo Feitosa. “Ranging from 30 to 65%.” Deep-water species, like sleeper sharks, suffered from the trauma of rapid pressure shifts, making their survival after release unlikely.

Limits of retention bans

Simulating different policy scenarios, the researchers found that retention bans could reduce shark mortality by three times on average. However, this reduction was still not enough to ensure the sustainability of heavily fished species, such as mako and silky sharks.

“Retention bans are a beneficial first step towards addressing shark overfishing,” said Bradley.

But he warned that these bans alone will not be enough. Additional conservation measures, such as restricting certain fishing areas, setting catch quotas, and regulating fishing gear, must be implemented to ensure long-term population stability.

Certain shark species, such as blue sharks, bonnetheads, and angel sharks, have a better chance of recovering due to their faster reproductive rates. However, even the blue shark, which is the most heavily fished shark species globally, remains vulnerable.

“While it is highly unlikely that retention bans will ever be implemented for such a commercially important species, our results show that this could be a relatively simple and impactful strategy if it becomes necessary to sustain populations,” said Feitosa.

More rules are needed to protect sharks

For many shark species, retention bans alone will not be enough. To make a real impact, conservation strategies must focus on reducing the number of sharks caught in the first place.

One approach is to ban the use of steel wire on longlines, which increases the likelihood of sharks becoming entangled in fishing gear.

Spatial regulations could also help. Designating certain areas as shark nurseries and pupping grounds and restricting fishing in these zones would give young sharks a chance to grow and contribute to the population.

Protecting these critical habitats could make a significant difference in sustaining species that are struggling to recover.

Another challenge is the lack of data on other cartilaginous fish species, such as stingrays, skates, and chimaeras.

“Fifty-seven percent of cartilaginous fishes threatened with extinction in the world are not sharks,” Caughman explained. The team could not include these species in their study due to insufficient data, highlighting the need for further research.

Towards a sustainable future

Shark conservation requires cooperation among governments, scientists, and fisheries. Members of The Nature Conservancy are currently collaborating with the Inter-American Tropical Tuna Commission’s scientific staff to find effective strategies for shark protection.

These efforts aim to create well-informed policies that balance fishing needs with conservation goals.

The study serves as a call to action for the global community. Without stronger conservation strategies, shark populations will continue to decline, leading to widespread ecological consequences.

By combining various management approaches and investing in better data collection, scientists and policymakers can work toward a future where sharks remain an essential part of the ocean’s ecosystem.

The study is published in the journal Fish and Fisheries.

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