The world’s oceans are home to an exquisite variety of sharks and rays, from the largest fishes in the sea – the majestic whale shark and manta rays – to the luminescent but rarely seen deep-water lantern shark and guitarfishes. The oceans were once teeming with these extraordinary and ancient species, which evolved close to half a billion years ago. However, the past half-century has posed one of the greatest tests yet to their survival.