Chimaeras, or ghost sharks, are one of the most elusive fish species in the world, so marine biologists were ecstatic when they spotted a baby ghost shark during a survey of New Zealand's South Island coast.
"We don't actually know a lot about ghost sharks," Brit Finucci, a National Institute of Water and Atmospheric Research (NIWA) fisheries scientist, told CNN's Jeevan Ravindran. "What we do know mostly comes from adult specimens. So, it's very rare and very uncommon to find juveniles of a lot of these species, so that's why I got quite excited."
The neonate, or hatchling, was found at a depth of 3,940 feet (1,200 meters) on the Chatham Rise located east of New Zealand, reports Brandon Specktor for Live Science. NIWA researchers were surveying blue grenadier, or Hoki fish, with trawling nets at 4,000 feet deep when the ghost shark was accidently caught as bycatch, reports Gizmodo's George Dvorsky. The find can help biologists learn more about chimaeras and how they grow.
According to Shark Trust, ghost sharks—also known as ratfish, spook fish, or rabbitfish—are rarely seen by humans since most species are found at depths ranging between 200 to 2,600 meters along the seafloor. In recent decades, researchers learned the fish have existed for hundreds of millions of years, reported Annie Roth for the New York Times in 2020.
Related to sharks and rays, the ancient species diverged from these groups 300 million years ago, reported National Geographic's Jason Bittel in 2016. The fish do not have bones but instead are cartilaginous, meaning their bodies are riddled with stiff armor-like plates and bone-like cartilage, Gizmodo reports. Adult ghost sharks have venomous spines in front of their dorsal fins and can whip through the water by flapping their pectoral fins. According to the New York Times, most males reproduce through a retractable sex organ called a tenaculum on their foreheads.
There are about 52 known chimaera species, but researchers suspect more are out there. After female chimeras lay their egg capsules on the sandy seafloor or muddy seabed, the embryos will grow inside and feed off the egg capsules until it is ready to hatch. Depending on the species of ghost shark, it takes between 6 to 12 months for an embryo to hatch. The team suspects the ghost shark recently had hatched because its belly was still filled with egg yolk, a NIWA statement reports.
Researchers do not know the exact species of the baby shark and plan on running genetic tests to see what genus it belongs in, Live Science reports. As soon as researchers learn what species it is, they can compare it to an adult to learn more about its development from juvenile to mature.
Currently, it is unknown how long chimeras live and how often they reproduce. Critical missing details about the species' life cycle makes monitoring chimaera populations difficult, the New York Times reports. In a 2020 Fish and Fisheries study co-authored by Finnuci, researchers found 16 percent of all ghost shark species are threatened or near-threatened. Nearly 15 percent of ghost shark species are so understudied that ghost shark species may go extinct before researchers have time to study them.
It is possible that finding a juvenile fish may answer some questions about the species.
"From better-studied chimaera species, we know that juveniles and adults can have different dietary and habitat requirements. Finding this ghost shark will help us better understand the biology and ecology of this mysterious group of deep-water fish," Finucci explained in a statement.