Great white shark charges after a bait line. (Photo by Martin Prochazkacz on Shutterstock)

Research shows catch-and-release policies aren’t enough to slow trend

SANTA BARBARA, Calif. — Sharks are facing a global extinction crisis, with nearly one-third of all shark and ray species threatened worldwide. In response, many fisheries have implemented retention bans that require fishers to release any sharks they catch instead of keeping them. These bans seem like a straightforward solution, but new research shows they’re only part of the answer to preventing shark overfishing.

A new study published in Fish and Fisheries reveals that while requiring fishers to release sharks does reduce deaths, it’s not enough on its own to stop overfishing for many threatened shark species. Researchers analyzed data from 160 studies and found that even when sharks are released back into the ocean after being caught, many don’t survive the experience.

The Hidden Toll on Released Sharks

The study, led by researchers from the University of California Santa Barbara and Dalhousie University, examined how effective these release requirements are across different shark species and fishing methods.

For the 341 shark species analyzed, mandatory release resulted in about three times fewer shark deaths compared to keeping all caught sharks. However, for 18% of species studied, that reduction still wasn’t enough to prevent overfishing.

“Retention bans are a beneficial first step towards addressing shark overfishing,” says co-author Darcy Bradley, a scientist at The Nature Conservancy, in a statement. “But they need to be complemented with other strategies, such as area-based fishing restrictions, catch quotas, and fishing gear requirements to sustain populations for many shark species.”

The problem is that many sharks die either during capture before they can be released or after release due to injuries and stress. The study found that with longlines, fishing lines that can stretch for miles with hundreds or thousands of baited hooks, sharks experience an average 31.7% death rate during capture and another 23% die after release. This means that even when fishers follow the rules perfectly and release all sharks, more than half of some species may still die.

Some Sharks Are Hit Harder Than Others

“Mortality was surprisingly high for some species such as smoothhound sharks, ranging from 30 to 65%,” says co-lead author Leonardo Feitosa, a doctoral candidate from the University of California Santa Barbara.

Deep-water sharks also fared poorly, likely because of the trauma from extreme pressure changes when brought to the surface. Smaller sharks living in shallow waters were more likely to die during capture compared to deeper-dwelling species. Sharks that need to swim constantly to breathe (like many open-ocean species) had higher death rates than those that can rest on the bottom and pump water over their gills.

Hammerhead sharks were especially vulnerable, with an average of 56.1% dying during capture. Thresher sharks, mako sharks, and sand tiger sharks also suffered high death rates.

For the Critically Endangered sand tiger shark, mandatory release only reduced fishing deaths by about 1.5 times—not enough to prevent continued population decline.

However, some good news emerged. Certain threatened species benefited significantly from release requirements. The endangered sawback angelshark showed the greatest potential benefit, with almost 11 times fewer deaths under a release policy.

Better Ways to Protect Sharks

Release requirements work best for species that reproduce relatively quickly, like blue sharks and angel sharks, because their populations can bounce back faster. The blue shark is actually the most heavily fished shark worldwide.

“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,” says Feitosa.

When looking at real-world applications, the researchers analyzed 37 shark populations with known fishing pressure. They found that release requirements would effectively reduce fishing deaths to sustainable levels for more than two-thirds of these populations. However, this was mainly true for sharks that weren’t already heavily overfished.

For other sharks, keeping populations healthy will require more. Methods to reduce the number of sharks caught in the first place, such as banning steel wire leaders on fishing lines, which sharks can’t bite through, could work alongside release requirements. Protecting shark nurseries and breeding grounds could also help populations recover.

Most research on shark mortality has focused on industrial longline fisheries. We know much less about death rates in gillnet and trawl fisheries or about impacts on coastal sharks and rays. The team couldn’t include rays, skates, and other related species in their analysis because so little data exists on their survival rates.

“Fifty-seven percent of cartilaginous fishes threatened with extinction in the world are not sharks,” says co-lead author Alicia Caughman, a doctoral candidate at the University of California Santa Barbara.

Members of the research team are now working with the Inter-American Tropical Tuna Commission to apply these findings to real-world conservation efforts.

A Complete Approach to Shark Conservation

While requiring fishers to release sharks is a good start, it can’t be the only solution. Additional measures are needed, especially for slow-growing species already in decline. The most effective approaches will reduce the number of sharks caught in the first place, rather than just requiring their release after capture.

Despite the fear sharks may inspire in humans, they have far more reason to fear us. For sharks caught on fishing gear, simply being thrown back into the ocean isn’t always enough to save their lives.