The so-called “ghost shark” isn’t a shark, despite its informal name. Rather, it’s a chimaera, a rare species of fish that split off from sharks some 300 million years ago. And sightings of this fish are unusually rare, which is why a new sighting off the California coast has researchers’ interests piqued.
According to the Christian Science Monitor, chimaeras can usually be found near New Zealand and Australia, and the recent video sighting of the fish suggests that the range of one particular species may not be as limited as once thought. In the words of Pacific Shark Research Center at Moss Marine Laboratories program director Dave Ebert, it was mostly “dumb luck” when the sighting took place in 2009.
The video was taken that year when the Monterey Bay Aquarium Research Institute (MBARI) in California had sent a remotely operated vehicle to depths of up to 6,700 feet in the waters of California and Hawaii. At that time, the ROV was not specifically helping researchers look out for ghost sharks, which makes the sighting completely accidental.
After spotting the fish, the MBARI contacted Ebert and other experts, having noted that the ghost shark they had seen looked different from other known species. Based on the video, Ebert’s team deduced that the fish was a pointy-nosed blue chimaera, an extremely rare variant that has only been spotted in Australia and New Zealand.
While the “ghost shark” nickname is most commonly used when referring to the chimaera, the animal is also known unofficially as the ratfish or rabbitfish. Their appearance is more similar to that of fish from the time of marine dinosaurs and earlier, than it is to modern fish. They primarily favor the deep ocean, preferring its cold waters and mainly getting spotted in Southern Hemisphere waters. But this time around, the sighting took place in the Northern Hemisphere; if the fish in the video is confirmed as a pointy-nosed blue chimaera, that will mark the first time it has been seen in the area.
Speaking to National Geographic, Millersville University marine biologist Dominique Didier explained how hard it can be to collect chimaera specimens.
“The only way we can collect these species is by trawling. 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.”
The only way one can determine whether the ghost shark does actually exist in the Northern Hemisphere would be to get DNA from an actual fish, the National Geographic wrote. According to the publication, Ebert hopes to find new specimens at local fish markets, but as Didier had suggested, using a trawling boat would likely be far more effective in the search for specimens; chimaeras are usually dead once they are spotted at the surface.
Even without physical evidence, the researchers were able to glean a lot of information on the fish they had sighted. According to Ebert, the chimaera on the video was quite the “ham” when the remotely operated vehicle tried to get a close-up of it. The video also suggests that pointy-nosed blue chimaeras prefer rocky habitats to the flat terrain that ghost sharks usually favor.
The National Geographic report added some information on the chimaera’s peculiarities. The creatures tend to “munch up” mollusks, worms, and other bottom-dwelling prey with mineralized tooth plates, in the absence of teeth. The lateral line canals on their faces allow them to sense movement while in the water, helping them find their prey. And, in an especially interesting note, male chimaeras have retractable sex organs, located on their foreheads.
With all those peculiarities and the fish’s general rarity in mind, ghost sharks are, as Didier says, “just one of the many beautiful and poorly studied species” in the animal kingdom.
[Featured Image by Mandy Lindeberg, NOAA/Wikimedia Commons/Cropped and Resized/Public Domain]