We Haven't Seen This Species Of Shark Before In The Bahamas!
Oct 21, 2019, 11:23pm
We Haven’t Seen This Species Of Shark Before In The Bahamas!
Melissa Cristina Márquez Contributor
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.DIEGO CAMEJO
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 wasn’t known what species the Tongue of the Ocean was home to. So, down the BRUV went. “I’ve been developing BRUV technology over the past few years so I’m 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, ... [+]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 wasn’t 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.
More:
https://www.forbes.com/sites/melissacristinamarquez/2019/10/21/we-havent-seen-this-species-of-shark-before-in-the-bahamas/#13acfde3370c