Overfishing is Responsible for Global Shark & Ray Declines
A great white shark photographed in Kleinbaai, South Africa (2019) | Hannah Rudd ©
The number of sharks, rays, skates and chimaeras - known collectively as Chondrichthyes (cartilaginous fishes) at risk of extinction has more than doubled in less than a decade, with overfishing being the primary driver behind their decline.
Research published today in the journal Current Biology, is the second global assessment of Chondrichthyes and has uncovered some bleak statistics on the state of sharks and rays worldwide.
“Overfishing is the main risk for all threatened species of Chondrichthyes”
A third of shark, ray and chimaera species now qualify as being threatened with extinction according to IUCN Red List criteria, with rays being the most vulnerable group. It is possible that three Chondrichthyes species may already be extinct; the Red Sea torpedo, the lost shark and The Java Stingaree. Currently sawfishes, giant guitarfishes, devil rays and pelagic eagle rays face the most imminent risk.
100 million sharks are estimated to be killed every year. They are intentionally targeted for their meat and fins, and are also victims of bycatch - unintentional capture - where they may or may not be released (dead or alive) depending on relevant legislation. If retained as bycatch sharks may then go on to be processed as other products such as fish meal, animal feed, chondroitin (shark cartilage) or squalene (shark liver oil). The impacts of overfishing are made worse by the mounting threats of climate change, habitat loss and degradation, and pollution.
The global assessment released today found that shark and ray risk of extinction is disproportionate across the world. More than 75% of species within tropical and subtropical waters are threatened, with Indonesia being a hotspot for extinction risk. Within these regions there is a higher demand for shark and ray products and a higher dependency by local communities to fish for these creatures as a result. Fisheries management within these localities is also largely unregulated which is another contributing factor to the demise of sharks and rays.
Blue shark photographed offshore, Simons Town, South Africa | © Harry Stone
All hope is not lost though. Scientists have also provided further evidence to suggest that science-based fisheries management works and is a successful way of recovering populations. Going forward sustainable fisheries management must be implemented across fisheries internationally to ensure that shark populations can recover whilst the communities that have come to depend on them are also supported. It’s vital that governments of the world follow the science. We are drastically running out time. Extinction is forever and we must collectively take action before the window to do so closes.
Why are sharks and rays vulnerable?
Cartilaginous fishes are vulnerable to extinction due to their life history characteristics. They grow slowly, have a late sexual maturity and produce relatively few pups with each reproductive cycle. For example scientists estimate that it takes male great white sharks 26 years and females 33 years to reach sexual maturity. That is an incredibly long time to navigate an increasingly perilous ocean before having the opportunity to breed successfully for the first time.
Why are sharks important?
Sharks in particular are vital for ocean ecosystem health. As apex predators sharks fulfil an important role at the top of the food web by predating on the weak and sick species below them and maintaining competition between species to ensure strong genetic diversity. Sharks are in essence the doctors of the ocean. They are also an indicator of ocean health, and as a result, in the words of Dr. Sylvia Earle “you should be scared if you’re in the ocean and you don’t see sharks”.
Humanity depends on a healthy ocean and one component of that is a healthy shark population. As shark populations continue to be depleted across the world the socio-economic benefits they provide, be it through tourism, fishing opportunities and food security, are also put at risk. This will be particularly felt within vulnerable and marginalised communities within the Global South where sharks are a key contributor to economic and food security. It’s therefore in all our interests to follow the science and advocate for sustainable fisheries management across the world.