River shark

The genus *Glyphis* contains a group of animals known as river sharks. These sharks belong to the family Carcharhinidae. They are distinct from the bull shark, which is also sometimes called a river shark. While bull sharks and *Glyphis* sharks may live in the same river systems, they are different groups. These sharks are unique because they inhabit rivers and coastal regions. They are often found in parts of Southeast Asia and Australia. Some reports even place them in the Zambezi River in Africa.

River sharks prefer very specific environments to survive. They are often found in nine different tidal areas. These areas usually consist of muddy waters with low salinity. Salinity refers to the amount of salt present in the water. Some species stay in freshwater environments. For example, the Ganges shark is restricted to freshwater. Other species, like the northern river shark and the speartooth shark, can also live in coastal marine waters. Their presence in coastal areas suggests they are usually born around October.

Scientists use taxonomy to organize and name the different species within *Glyphis*. The genus is considered to be most closely related to the genus *Lamiopsis*. Currently, there are several recognized species in this group. These include the Borneo river shark, the Ganges shark, the northern river shark, the speartooth shark, and the Irrawaddy River shark. There are also known extinct species, such as *Glyphis hastalis* and *Glyphis pagoda*. The exact number of species might be higher than what scientists currently accept. However, the secretive habits of these sharks make research very difficult.

Taxonomy is a changing field as new studies provide more information. Scientists once thought there were five different species in this genus. Later, molecular studies changed this understanding. These studies revealed that *Glyphis gangeticus* has an irregular distribution in the Indo-West Pacific region. Because of this, the Bornean and Irrawaddy River sharks may actually be variations of *Glyphis gangeticus*. Despite these findings, some scientific authorities still choose to keep these species separate.

History shows how long humans have been studying these animals. The Ganges shark was first described by J. P. Müller and Henle in 1839. The Irrawaddy River shark was named by Steindachner in 1896. Other species have been identified much more recently. For instance, Compagno, White, and Cavanagh described the Borneo river shark in 2010. For a long time, researchers actually believed these sharks were extinct. It was not until the end of the 20th century that small populations were rediscovered in Borneo and Northern Australia.

Conservation is a major concern for the survival of river sharks. Many populations are currently very poorly known to researchers. The Ganges shark uses the Ganges River as nursery grounds. A nursery is a place where offspring are born and raised. Unfortunately, these populations have been severely diminished. This decline is caused by a long history of fishing and pollution issues in the Northern Arabian Sea. These environmental pressures make it difficult for the sharks to maintain healthy numbers.

Fishing activity also plays a significant role in shark populations. India is a major location for these activities. It is reported to be one of the top three greatest shark and ray capturers in the world. In fact, India accounts for up to nine percent of reported global landings for these animals. This high level of fishing, combined with pollution, creates a difficult environment for the genus *Glyphis*. Understanding their distribution and habitat is vital for protecting these secretive creatures.