Why Half of All Sharks Have Vanished Since 1970

Sharks have ruled the oceans for over 400 million years, long before dinosaurs walked the Earth. These fascinating creatures are powerful predators that keep our oceans healthy and balanced. But something really troubling is happening: since 1970, the global population of sharks has dropped by over 50%—and in some regions, it’s even worse. So, why are sharks disappearing at such an alarming rate?

In this post, we’ll dive deep into the reasons behind this shark crisis, explore what it means for the ocean, and learn how we can help turn things around. Let’s explore the mystery of the vanishing sharks.

A Big Drop in Numbers: What the Science Says

Back in 2021, a massive study revealed something shocking. Researchers from around the world looked at data from 1970 to 2018 and found that the population of oceanic sharks and rays had dropped by 71% in just under 50 years (Pacoureau et al., 2021). That’s more than half—and in some cases, nearly three-quarters—of all these species gone in just one human lifetime!

Sharks that live in open waters, like the hammerhead, great white, and oceanic whitetip, have been hit especially hard. The same study found that three-quarters of shark species in this group are now threatened with extinction.

But what’s behind this massive drop?

Reason #1: Overfishing and the Shark Fin Trade

The biggest reason sharks are disappearing is simple: people are catching way too many of them.

In the 1970s, fishing technology became more advanced, with larger boats, stronger nets, and deeper longlines. That made it easier to catch sharks—even the ones living far offshore. Sharks are often caught on purpose for their meat, liver oil, and especially their fins. In other cases, they’re caught accidentally in nets and lines meant for other fish like tuna or swordfish.

The shark fin trade is especially deadly. Shark fins are used to make shark fin soup, a delicacy in some Asian countries. It’s a huge market—tens of millions of sharks are killed each year just for their fins. Often, the fins are cut off, and the rest of the shark is thrown back into the ocean, sometimes still alive but unable to swim. This practice, called “finning,” is both cruel and wasteful (Dulvy et al., 2014).

Because many sharks grow slowly, have long lifespans, and give birth to just a few pups, their populations can’t recover quickly from heavy fishing. That’s a recipe for disaster.

Reason #2: Bycatch—Sharks Caught by Accident

Sometimes, sharks aren’t even the target of fishing boats. They’re caught as “bycatch,” which means they get hooked or tangled in gear meant for other fish. This happens a lot in commercial tuna and swordfish fisheries. Once caught, many sharks don’t survive the ordeal, even if they’re thrown back (Oliver et al., 2015).

In fact, some studies estimate that up to 50% of all sharks killed each year are caught accidentally (Lewison et al., 2004). Even worse, most of the bycatch isn’t even reported, so the true numbers could be much higher.

Reason #3: Habitat Loss

Just like land animals need forests and rivers, sharks need healthy oceans. And just like we’re losing rainforests on land, we’re also damaging shark habitats in the ocean.

Mangroves, coral reefs, and seagrass beds are super important for many types of sharks, especially young ones. These areas act like nurseries where baby sharks can grow up safely. But pollution, coastal development, and climate change are destroying these critical habitats (Heithaus et al., 2007).

When sharks lose their homes, they have fewer places to hide, hunt, and raise their young. That makes it harder for them to survive.

Reason #4: Climate Change and Warming Oceans

The ocean is changing. As climate change heats up our planet, it’s also heating up the seas. That affects everything from the food sharks eat to the places they can live.

Warmer water can force sharks to move to new areas, sometimes into places where they’re more likely to be caught by fishermen. It also affects their prey, which might become harder to find (Rosa et al., 2014).

Climate change is also causing coral bleaching, sea level rise, and ocean acidification—all things that make it tougher for sharks to thrive.

Reason #5: Lack of Protection and Weak Laws

Until recently, sharks weren’t protected by many laws. While countries have laws to manage fishing for popular species like tuna or cod, sharks were often overlooked. Even now, many countries don’t have strong rules to stop overfishing, ban shark finning, or protect threatened species.

Only about 17% of shark species are protected under international law (Dulvy et al., 2021). And enforcement is often weak. That means illegal fishing and unreported catches still happen a lot.

Even when protected areas exist, they may not be big enough or properly monitored to help shark populations recover.

Why It Matters: Sharks Keep the Ocean in Balance

Sharks aren’t just scary teeth swimming in the sea—they’re a super important part of ocean ecosystems. As apex predators (top of the food chain), they help keep everything else in balance. Here’s how:

• Controlling prey populations: Sharks eat sick, weak, or slow fish, which keeps fish populations healthy.
• Balancing ecosystems: By preying on mid-level predators, sharks help protect the animals lower in the food chain, like herbivorous fish that clean coral reefs.
• Supporting healthy habitats: In places like seagrass beds and coral reefs, sharks help keep things from getting out of control by maintaining the natural order.

When sharks disappear, the whole ocean food web can get thrown off. For example, when shark numbers drop, mid-sized predators like rays can boom—and they may eat too many shellfish like scallops or clams, hurting both the ecosystem and local fisheries (Myers et al., 2007).

Some Sharks Are in Bigger Trouble Than Others

While all sharks face threats, some are worse off than others. Open-ocean sharks like the oceanic whitetip, shortfin mako, and thresher sharks have seen some of the sharpest declines.

Hammerhead sharks, known for their amazing head shape and incredible senses, have also been hit hard. The scalloped hammerhead is now listed as critically endangered by the International Union for Conservation of Nature (IUCN, 2024).

Large sharks like the great hammerhead and dusky shark are especially vulnerable because they grow slowly and take many years to reproduce. Even a few years of heavy fishing can crash their populations.

What’s Being Done to Help?

It’s not all bad news! People are working hard around the world to protect sharks. Here are some hopeful developments:

1. Shark Sanctuaries

Some countries have created shark sanctuaries where no commercial shark fishing is allowed. Nations like Palau, The Bahamas, and the Maldives have protected their waters, giving sharks safe places to live and reproduce.

2. Fishing Bans and Catch Limits

Some regions now limit how many sharks can be caught or ban the most endangered species entirely. For example, the EU banned fishing for porbeagle sharks and now requires shark fins to remain attached to the body when landed—this helps stop finning.

3. CITES and Global Treaties

The Convention on International Trade in Endangered Species (CITES) now includes protections for many shark species. This means their parts can’t be traded internationally without permits that prove the fishing was sustainable (Lawson & Fordham, 2018).

4. Marine Protected Areas (MPAs)

MPAs are special zones where fishing is limited or not allowed at all. When done right, these areas can help shark populations recover. Studies have shown that MPAs can lead to more sharks, bigger sharks, and better biodiversity (Robbins et al., 2006).

What Can You Do to Help Sharks?

Even if you don’t live near the ocean, you can still make a big difference! Here are some ways to help:

• Avoid shark fin products. Don’t eat or buy anything made from shark fins.
• Choose sustainable seafood. Look for seafood that’s certified by the Marine Stewardship Council (MSC) or recommended by organizations like Seafood Watch.
• Support shark conservation groups. Groups like Shark Trust, WildAid, and Shark Advocates International are fighting to protect sharks worldwide.
• Educate others. Share what you know with friends, family, or classmates. The more people know, the more likely they are to care.
• Reduce plastic and pollution. Sharks live in oceans filled with plastic waste. Clean up beaches, use reusable items, and help keep oceans clean.

The Ocean Needs Its Sharks

Sharks have been swimming in Earth’s oceans for hundreds of millions of years. They’ve survived mass extinctions, ice ages, and giant meteors. But they may not survive us—unless we act.

We’ve already lost half of all sharks since 1970. But it’s not too late to change course. By understanding the problem, spreading awareness, and pushing for better protection, we can give sharks a fighting chance.

Because saving sharks isn’t just about protecting one animal—it’s about saving the health of the whole ocean.

Bibliography

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