Swimming to extinction

Sharks that use a whip-like tail to stun their prey and river rays half the length of a bus are among the most unique species at risk of extinction according to the latest ranking from ZSL’s EDGE of Existence programme.

The new list ranks the world’s 50 most Evolutionarily Distinct and Globally Endangered (EDGE) sharks, rays and chimeras – known collectively as Chondrichthyes. Each species on this list has few or no remaining close relatives; if they go extinct, we will have nothing like them left on the planet.

Many of these species are threatened by fishing for shark fins or caught unintentionally (bycatch). Other threats include habitat degradation due to coastal development and pollution. The new EDGE list gives conservationists a tool to prioritise species where there is the most pressing need for action.

ZSL’s Marine and Freshwater Conservation Programme Manager, Dr. Matthew Gollock said: “The EDGE Sharks and Rays list comprises some of the most interesting and unique fish we have on this planet. The modern extinction of a single species from this list would cause the loss of millions of years of evolutionary history.”

Highlights from the list include:

The largetooth sawfish (Pristis pristis) – has the highest-ranking score across all EDGE species. Uses an elongated snout (rostrum) lined with teeth on each side to slash at its prey, the largetooth sawfish is facing threats from unsustainable fishing activities.

Caribbean electric ray (Narcine bancroftii) – uses an electrical charge to stun their prey.

Whale shark (Rhincodon typus) – Whale sharks are the biggest fish in the sea.

Zebra shark (Stegostoma fasciatum) – The zebra shark gets its name from the pattern of its babies, that have striking black and white stripes on them, which changes to spots as they get older.

Giant freshwater whipray (Urogymnus polylepis) – An enormous ray that can reach sizes half the length of a bus.

Ornate eagle rays (Aetomylaeus vespertilio) – These rays are very strong swimmers, jumping out of the water several metres high.

Honeycomb izak (Holohalaelurus favus) – This catshark can only be found off the coasts of South Africa and Mozambique. Once regularly caught in trawl fisheries, it has not been seen since the 1970s.

Blackchin guitarfish (Glaucostegus cemiculus) – They are now extremely rare with fins highly priced in the Asian fin market, selling for over £90/Kg (USD $114/Kg).

Sand tiger shark (Carcharias taurus) - Sand tiger sharks have a rather gruesome reproductive technique called intrauterine cannibalism; embryos develop teeth and eat each other, leaving a litter of just two pups, one in each uterus.

Angel shark (Squatina squatina) – The angel shark family (Squatinidae) has been declared the most threatened of all sharks and rays’ families after sawfishes. Their ability to camouflage themselves rivals that of a chameleon.

Dr. Matthew Gollock said: “Since 2013, we have been working in collaboration with partner organisations in the Canary Islands for the conservation of the angel shark (Squatina squatina), #5 in the EDGE list, increasing our knowledge of this species and working with divers, fishers and policymakers to improve management and policy.

“Our successes from this project have allowed us to expand our work to Wales (UK), where we have taken a similar stakeholder-lead approach to collect sightings and community memories of the angel shark in order to better understand and conserve this Critically Endangered species across its range.”

Find the full ranking of EDGE Sharks and Rays here: www.edgeofexistence.org/sharks-and-rays

ZSL will be streaming a live webinar (5pm 4^th December 2018) about the EDGE Sharks & Rays list. Hear from expert speakers from around the world, such as Nicholas Dulvy Co-Chair of the IUCN SSC Shark Specialist Group and Joanna Barker, Coordinator of the Angel Shark Project. The EDGE team will be explaining some of the quirky details, threats and conservation actions we hope to see for the EDGE sharks and rays.

Watch the webinar here: https://www.edgeofexistence.org/sharks-and-rays-webinar/