This Species Of Shark Was Spotted For The First Time In The Tongue Of The Ocean Near The Bahamas – Forbes

Posted: October 24, 2019 at 11:38 am

Using a baited remote underwater video system (BRUV), a team of scientists led by Assistant Professor Brennan T. Phillips of the University of Rhode Island has provided the first recorded in situ observation of the sharpnose sevengill shark (Heptranchias perlo) from the Tongue of the Ocean, Bahamas.

Gallery of BRUV video stills of individual H. perlo, filmed at 718 m depth.

Distributed in tropical and temperate regions, these sharks are almost circumglobal in their range. As a deepwater species, they are often observed on the outer continental and insular shelves at depths from 89 to 3280 feet (27-1000 m). Usually found on or near the bottom, sharpnose sevengill sharks are voracious predators that feed on a variety of animals such as shrimp, crabs, lobsters, squid and cuttlefish, small bony fish, and small sharks and rays. The smallest hexanchoid shark, they grow to a maximum length of 4.5 feet (1.37 m) total length for males and 4.6 feet (1.40 m) total length for females. With a narrow head, bright green eyes, comb-shaped teeth, and seven gill slits, it is a distinct looking shark that has never been seen in the tropical waters of the Bahamas.

The Tongue of the Ocean is a large (25 miles wide, 124 miles long), semi-enclosed deep ocean trench separating the islands of Andros and New Providence. The southern portion of the Great Bahama Canyon, little is known of what life is here, with abundance and diversity estimates available for only some deepwater corals and sponges. And while the nearby Exuma Sound has notable recent chondrichthyan (shark, skates, rays, and chimaeras) observations, it wasnt known what species the Tongue of the Ocean was home to.So, down the BRUV went. Ive been developing BRUV technology over the past few years so Im always looking for interesting projects to deploy them on, so I can keep pushing with my tech development. Dr. Austin Gallagher has been working the Bahamas for a long time as a shark researcher [with Beneath the Waves], and wanted to bring in more deep-sea science it turns out that a lot of shallow-water sharks actually dive quite deep for feeding and mating, so the idea was to try and get some visual imagery of them at depth, explained Phillips.

UNSPECIFIED - OCTOBER 08: Fishes: Hexanchiformes Hexanchidae, Sharpnose sevengill shark, ... [+] (Heptranchias perlo), illustration (Photo by De Agostini via Getty Images/De Agostini via Getty Images)

BRUVs are stationary, seafloor camera stations that use bait to attract fish in their vicinity, recording the species attracted to the bait or swimming past the camera lens. The camera is held in a steel frame that allows for some protection from animals that bite at the nearby bait or the camera itself. With this tech, scientists can observe fish in hard-to-reach habitats in both shallow and deep waters, such as the Tongue of the Ocean. The individual sharpnose sevengill shark, a male, was recorded at a depth of 2355 feet (718 m) and was estimated to have a total length of approximately 3.3 feet (1 m). With that length, it means this is a mature male capable of mating with any mature females. However, no other sharks, let alone female sharpnose sevengills, were recorded during this BRUV deployment.

The lone mane circled the BRUV for about 10 minutes and then left. This wasnt the only exciting discovery, however, for the team of scientists. Temperature recordings of about 48.24 F (9.02 C) at this depth indicate that sharpnose sevengill sharks are physiologically capable of thriving within the lower mesophotic zone. This oceanic zone is known as the middle light zone due to it being a world between worlds - between light and inky darkness and varied marine life calls this region home.

The results, the authors of this study emphasize, underscore the need for further research into deepwater chondrichthyan biology in the Bahamas. Its the first time the species has been seen in situ all previous knowledge about this shark has been gained using traditional fishing methods (catch the shark on a line, and pull it up to learn more).Our observation shows it goes pretty deep (>700m) and also it qualifies as a range extension, since it hasnt been seen before in The Tongue of the Ocean, said Phillips.We have very, very limited data on deep-sea shark diversity so this observation just adds to our knowledge base, which is thin (at best).It is entirely possible that this species goes much deeper than 700m, and is more widely distributed in the Bahamas in general.

Thankfully this kind of research can be readily facilitated by BRUV-based methods. Phillips is excited to see what more can be discovered with this marine technology, saying: I think BRUVs are an important tool for discovery for several reasons.First, they are compact and can be run off small vessels.They are also relatively cheap (<$10k per system) allowing for scientists to deploy multiple systems at the same time.They are simple to operate too, no extensive training is required.For all of these reasons, a wider user base can access BRUVs as a scientific tool allowing for a more democratizeddeep-sea research community (e.g. the My Deep-Sea, My Backyard initiative).

Hopefully more BRUVs will be deployed in the deep waters of the Bahamas in the near future to uncover more shark secrets.

Update: The headline of this story was modified after publication to be specific to the Tongue of the Ocean, as the sharpnose sevengill shark has been spotted near the Bahamas before - just not in this region.

Go here to see the original:

This Species Of Shark Was Spotted For The First Time In The Tongue Of The Ocean Near The Bahamas - Forbes

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