The Conservation Report

When most people think of a freshwater or river shark they recall the bull shark (Carcharhinus leucas). However, bull sharks are not true freshwater or river sharks. True freshwater sharks belong to the genus Glyphis. The genus Glyphis seems to prefer freshwater, but some species can probably tolerate different degrees of salinity while others may be entirely freshwater. Virtually nothing is known of river shark life history or geographical distribution, and all species of river shark are very rare and poorly described. In fact, many are known only from a handful of specimens or even a single specimen. Currently, there are about six known species of river shark, and most are undescribed or have not been formally described. The known species include:

1. Bizant river shark (Glyphis sp. nov. A)
2. Borneo river shark (Glyphis sp. nov. B)
3. Ganges shark (G. gangeticus)
4. Irrawady river shark (G. siamensis)
5. New Guinea or Northern river shark (Glyphis sp. nov. C)
6. Speartooth shark (G. glyphis )

River sharks seem to only be found in fresh or slightly brackish water. As a result, river sharks are most likely very susceptible to anthropogenic activities like coastal development, since they are specialists amongst elasmobranches or cartilaginous fish such as rays, sharks, and skates. Agriculture runoff, coastal development, fishing, industrial pollution, and sewage discharge certainly are threats to all species of river sharks. Researchers believe that river sharks have a low, minimum population doubling time, so recovery from negative impacts is probably very difficult for all species. To facilitate conservation efforts, researchers are currently working to improve river shark description through genetic studies. From Charles Darwin University, Australia:

Forensic scientist Dr Louise McMahon recently completed research on the identification and genetics of the threatened genus of shark called Glyphis.

Glyphis is a nationally and internationally threatened genus of shark about which scientists know very little. However, it is believed there are five possible species in the world, two of which occur within Australia (Glyphis sp. A and C)….

The research details the results into a preliminary assessment of genetic differences between two Glyphis species and several carcharhiniid species….

Her research on Glyphis has been submitted to the journal Marine and Freshwater Research for publication.

Public awareness campaigns are an important tool for conservationists working to save the river shark, because until people recognize river sharks “for what they are”, scientists risk losing important data from valuable specimens that may end up as food on the dinner table. From The Mysterious, Endangered River Sharks:

River sharks are not always recognized for what they are: extremely rare, little known wildlife. So few specimens are available for study that the loss of even one is a great blow to scientific and conservation efforts. In 1986, a Glyphis was caught by an angler in fresh water about 60 km upstream the South Alligator River, in Australia’s Northern Territory. Although the jaws were retained, this priceless specimen was eaten by the angler who caught it, resulting in the loss of much valuable data.

Here’s hoping that, as more and more people become aware of them, the drive to protect and conserve river sharks — and their habitats — will grow. River sharks may not be particularly dangerous or flashy, but they are rare creatures that add to the diversity and mystery of our world.

IMAGE: Borneo river shark

IMAGE: Glyphis spp. versus carcharhinid shark species

IMAGE: Glyphis spp. identification

References:

1. Glyphis n.sp. A Shark Once Feared Extinct is Rediscovered !
2. The Mysterious, Endangered River Sharks
3. Ever caught one of those sharks in the freshwater?
4. Gangetic sharks face extinction
5. Glyphis sp. A (Freshwater Speartooth Shark or Bizant River Shark) and Glyphis sp. C (Northern River Shark)
6. Freshwater and Estuarine sharks

Image Found Here
Image Found Here
Image Found Here

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