A ghost shark has been caught on film for the first time ever. Footage was captured during a dive using a remote operating vehicle off the coast of California in 2009, but has only recently been released following extensive analysis of the species seen.
Ghost sharks, also known as chimaeras, largely live in the deep sea – down to depths of more than 2,500m – so are rarely seen alive. They branched off from sharks between 300 and 400 million years ago and there are around 50 living species currently known to science.
They have long soft bodies and grow up to 1.5m in length. One of their most unusual features is seen on male ghost sharks – they have a retractable penis on their forehead.
Scientists at the Monterey Bay Aquarium Research Institute sent the remotely operated underwater vehicle (ROV) on dives down to 2,000m in waters off California and Hawaii. The species they saw was one that had previously been identified living in the Southeastern Pacific – specifically around Australia, New Zealand and New Caledonia.
But the species, Hydrolagus trolli – or pointy-nosed blue chimaera – had never been found in the Northern Hemisphere, and had never been seen on film before.
Dave Ebert, programme director for the Pacific Shark Research Center at Moss Landing Marine Laboratories, told National Geographic: "The guys doing the video were actually geologists. Normally, people probably wouldn't have been looking around in this area, so it's a little bit of dumb luck."
The ghost shark spotted did not resemble any of the species normally seen in these waters, so experts weighed in, analysing the footage. Publishing their report in the journal Marine Biodiversity Records, experts said it looks very much like a pointy-nosed blue chimaera, although without a specimen they could not know for definite.
If it is a pointy-nosed blue chimaera, this would show this species has a much larger range than previously thought. Marine biologist Dominique Didier said: "The only way we can collect these species is by trawling," she says. "So, it's like a snapshot. Imagine trying to understand species distribution in Lake Michigan and you sample the lake using a Dixie cup. Trawling the ocean is like that. I suspect many species are wide-ranging — we just don't have the data."