These so-called “river sharks” of the genus Glyphis are some of the most rarely seen, poorly understood, and critically endangered sharks on Earth.
Recognizable by their relatively small eyes, Glyphis sharks are found in large rivers and in nearby coastal ocean habitats in parts of the Indo-Pacific including Northern Australia, Papua New Guinea, Indonesia, India and Pakistan. “The bull shark and the river sharks in the genus Glyphis are the only sharks that can live in freshwater for extended periods of time, although many other sharks can tolerate estuarine conditions to different degrees,” said Gavin Naylor of the College of Charleston, a study co-author.
Though 24 percent of all known species of sharks and their relatives are considered threatened with extinction by the IUCN Red List, Glyphis sharks are in particularly bad shape. They are threatened not only by the overfishing that affects many shark species, but by habitat destruction caused by dams and other coastal development and pollution. It can also be difficult to raise public support for lesser-known species. “The surge in public support for shark conservation is deeply encouraging, but does still tend to focus on the largest, most charismatic species,” said Sonja Fordham, president of Shark Advocates International. “Securing protections for the hundreds of smaller, more obscure yet at-risk species can be tough.”
The research expedition that identified the sharks was part of a multi-year collaborative effort to bring shark experts from the U.S. and Australia to biodiversity hotspots with relatively low scientific infrastructure, including Papua New Guinea, Indonesia and Borneo. “The main aim of the project is to provide the necessary information on the shark and ray resources of Papua New Guinea to enable Papua New Guinea to manage its shark and ray resources on a sustainable basis,” said Will White of the CSIRO Australian National Fish Collection, the study’s lead author. “This is critical from a regional perspective as many shark species have ranges which cover multiple countries, thus we need to understand what pressure is on their populations throughout their range to be able to properly manage their stocks.”
An important step in protecting a species is gathering scientific data about their population distributions. “In the last decade or so, increased research on the two species which occur in northern Australia has drastically improved our knowledge on this group of sharks and will allow for more directed management plans to be developed,” White said. His team will continue to work with local villagers to study the Glyphis sharks of Daru, as well as other threatened and understudied species throughout the Indo-Pacific.
David Shiffman is a Ph.D. candidate at the University of Miami, where he studies the ecology and conservation of sharks. He writes about marine science and conservation for the blog Southern Fried Science as well as for Scientific American, Slate, and Gizmodo. Follow him on Twitter and Facebook.