Many species of sharks are still a mystery to scientists and rarely provide insight into their secret lives. Among them is certainly the Greenland shark (Somniosus microcephalus), which is probably one of the least studied sharks. Until now, it was assumed that Greenland sharks, which belong to the family of sleeper sharks, primarily reside in Arctic waters of the North Atlantic. Occasionally they are observed further south. Now it has been reported that a Greenland shark has been spotted in a region where the animals are probably least expected – near Belize in the western Caribbean off the second longest barrier reef on Earth. The report on this discovery was recently published in the journal Marine Biology.
Florida International University doctoral student Devanshi Kasana was actually out around Glover’s Reef Atoll with local fishermen tagging tiger sharks (Galeocerdo cuvier). When they checked the lines again at dawn, instead of a tiger shark, they spotted what looked like an “elongated, smooth stone that had sprung to life”. This and other features such as the blunt snout and small, pale bluish eyes led the team to suspect that it must be a representative of the sleeper shark family.
“At first, I was sure it was something else, like a six gill shark that are well known from deep waters off coral reefs,” Kasana said in a news release. “I knew it was something unusual and so did the fishers, who hadn’t ever seen anything quite like it in all their combined years of fishing.”
After consulting Damian Chapman, director of the Shark and Ray Conservation Research at Mote Marine Laboratory & Aquarium and Kasana’s doctoral advisor, and several Greenland shark experts, it was determined that it definitely belonged to the sleeper shark family. They believe that based on its size – between three and three and a half meters – it is most likely a Greenland shark or a hybrid between a Greenland shark and a Pacific sleeper shark (Somniosus pacificus). Greenland sharks grow extremely slowly and can live several hundred years.
Experts do not assume that the shark got lost, but rather suspect that Greenland sharks travel throughout the world ocean and in warmer regions, particularly at greater depths where temperatures are low. Because so little is known about the species, nothing can be ruled out.
The waters where Kasana and the fishermen found the shark are quite deep. Glover’s Reef Atoll – part of the Glover’s Reef Marine Reserve, a World Heritage Site – sits on a limestone platform and forms a lagoon surrounded by a coral reef. Along the edges of the atoll there is a steep slope that drops from almost 500 meters to 2,900 meters deep. So there is definitely cold water there that Greenland sharks need to thrive.
“I am always excited to set my deep water line because I know there is stuff down there that we haven’t seen yet in Belize, but I never thought I would be catching a Greenland shark,” said Omar Faux, one of the Belize fishermen.
In case another sleeper shark is caught during tiger shark tagging operations, the world’s leading expert on Greenland sharks – Nigel Hussey, associate professor of biology at the University of Windsor – has provided the research team with four satellite transmitters to learn more about the animals’ distribution.
Julia Hager, PolarJournal
Link to the study: Kasana, D., Martinez, H.D., Faux, O. et al. First report of a sleeper shark (Somniosus sp.) in the western Caribbean, off the insular slope of a coral atoll. Mar Biol 169, 101 (2022). https://doi.org/10.1007/s00227-022-04090-3
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