Overfishing has caused a 50% decline in sharks and rays

Since 1970, over half of all sharks and rays have vanished from our oceans, according to a new study. This alarming decline in sharks and rays stems primarily from overfishing, which has pushed these ancient and ecologically critical species to the brink.

However, researchers offer hope with clear strategies to halt further losses and support recovery efforts.

The scale of decline

The research highlights that overfishing has caused a 50% decline in chondrichthyan fishes – a group comprising sharks, rays, and chimeras. This diverse group of over 1,199 different species faces increasing threats despite advances in our understanding of these creatures.

“In addition to intentional targeting and bycatch, the threat to sharks is compounded by habitat degradation, climate change, and pollution,” noted Professor Colin Simpfendorfer from James Cook University in Australia.

“The result is over one-third of chondrichthyans now face the threat of extinction.”

Sharks and rays: Guardians of aquatic ecosystems

The disappearance of sharks and rays threatens the balance of aquatic ecosystems worldwide.

Lead author Professor Nicholas Dulvy from Simon Fraser University in Canada notes that population declines began in rivers, estuaries, and coastal waters before spreading to open oceans and deep seas. These marine creatures play vital roles in their environments.

“Sharks and rays are important predators, and their decline disrupts food webs throughout the ocean,” said Dr. Nathan Pacoureau from the European Institute for Marine Studies at Brest University, France.

“Larger wide-ranging species connect ecosystems. For example, reef sharks transfer nutrients from deeper waters to coral reefs, helping to sustain those ecosystems. Rays are important foraging animals that mix and oxygenate sediments, influencing marine productivity and carbon storage,” explained Pacoureau.

Without these keystone species, aquatic ecosystems could face severe disruption.

Impacts of overfishing on sharks

Overfishing – the practice of catching fish faster than they can reproduce – remains the leading driver of shark and ray declines.

The United Nations Food and Agriculture Organization (UNFAO) reports that one-third of the world’s fisheries are operating beyond sustainable limits, and the number of overfished stocks has tripled in the last 50 years.

Bycatch, the unintended capture of non-target species, exacerbates the crisis. Sharks and rays frequently end up as unintended victims in nets meant for other fish, which compounds their population losses.

Recovery from overfishing

Despite these challenges, the solutions for addressing the decline are straightforward.

“Nations can reduce the extinction risk by lowering fishing pressure to sustainable levels, strengthening fisheries governance, and eliminating harmful subsidies,” said Professor Simpfendorfer.

Some regions have already made progress. Countries such as Australia, Canada, New Zealand, the United States, and parts of Europe and South Africa have implemented science-based limits on fishing catches.

These measures include efforts to reduce bycatch and protect critical habitats, thus offering a glimmer of hope for chondrichthyan recovery.

Protecting sharks and rays from overfishing

The study highlights the urgency of collective action to safeguard these ancient species. Science-driven policies and international cooperation are vital to ensuring sharks and rays do not slip further toward extinction.

By addressing overfishing and habitat degradation for sharks, humanity can help restore balance to marine ecosystems and protect these vital guardians of the ocean.

More about sharks and rays

Sharks and rays belong to the group of cartilaginous fishes, known scientifically as Chondrichthyes.

Unlike bony fishes, their skeletons consist entirely of cartilage, making them lighter and more flexible. This evolutionary adaptation has helped them dominate aquatic ecosystems for over 400 million years.

Sharks, ranging from the tiny dwarf lantern shark to the massive whale shark, exhibit incredible diversity. Rays, their flat-bodied relatives, thrive in environments from shallow waters to the deep ocean floors.

Their unique physiology, including electrosensory systems, allows them to detect prey hidden under sand or at great distances from them.

Reproductive strategies among these species are equally fascinating. Some, like the great white shark, give birth to live young, while others, such as skates, lay egg cases commonly called “mermaids’ purses.” These long gestation periods and low offspring numbers make them highly vulnerable to overfishing and habitat changes.

Cultural significance in coastal communities

Beyond their ecological importance, sharks and rays hold significant cultural importance in many coastal communities around the world, often symbolizing power, protection, and the balance of nature.

Sharks and rays are also a major component of traditional diets in these communities, highlighting the need to balance conservation with livelihoods that are dependent on sustainable fishing.

The research was published in the journal Science.

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