Sharks are usually considered and imaged as brutal and fierce species. However, according to study led by Worm in the journal Marine Policy more than 100 million sharks are killed each year by humans. As a consequence, more than thirty percent of sharks have declined worldwide.
International Union for Conservation of Nature (IUCN) classified more than fifty percent sharks are threatened to extinction species. Researchers agree that shark fining is not the only culprit in shark declining but it be the one humans have the most direct influence. Not to mention, it duets with unsustainable fishing practices and bycatch. Additionally, the relatively slow growth rates and low maturity rates have made sharks even more severe.
Recently, global concern of shark is increase. Even so, knowledge about sharks are still lacking such as about population dynamic, migration area and species identification. Further, more than forty percent sharks, skates, rays, inhabit the deep ocean. One of them is sixgill shark. Sixgill shark typically inhabit in more than 200 m depth, both tropical and temperate oceans. Many studies have been hindered by their inaccessible habitat and the specimens are often difficult to get. As a consequence, miss-identification is commonly happened when it comes to identify the sixgill sharks. Therefore, scientists studied a detailed ecological and molecular examination as well as the distribution and biodiversity.
A team of scientists led by Toby Daly-Engel from Florida Institute of Technology has confirmed that sixgill species from Atlantic diverge from those in the Pacific and Indian Oceans. The new species has a new name called Atlantic sixgill shark (Hexanchus vitulus). Previously, it was thought that these sharks species are resemble as Indian-Pacific sixgill shark (H. nakamurai). An evidence from a recent publication in the journal of Marine Biodiversity reveals the differences between the two species.
Through genetic study using 1,310 base pairs, scientists confirmed that the two species are different. Study has been conducted in Belize, the northern Gulf of Mexico and the Bahamas from 2007 to 2016. In total, 45 sixgill sharks (H. vitulus and H. nakamurai) were captured. The sharks were measured fork length and total length. For genetic analysis, 0.5 cm fin clip has been sampled. Further, the genetic analysis was deployed and compared the genes (DNA sequences) with other studies. The finding highlighted that the two species i.e. Hexanchus nakamurai and Hexanchus vitulus are two distinct species.
As fishing efforts intensively and increasingly higher and move further into the deep ocean, it is very important to identify the species correctly to avoid misinterpretation of their status and resilience.