Among more than 400 species of sharks inhabiting oceans around the world, scientists have identified 5 species that are specialized for living in freshwater rivers and lakes.
To date, research on river sharks globally is quite limited. Scientists determine that most river sharks belong to the 5 species within the Glyphis family. Additionally, there is a possibility that many other shark species inhabiting freshwater areas have yet to be discovered by researchers.
River sharks can be found in freshwater regions in India, Southeast Asia, and various areas in Australia. However, they are rarely seen by humans.
Although they belong to the shark family, river sharks seem to be harmless to humans. Furthermore, activities such as fishing, environmental pollution, and rapid human development are seriously threatening the lives of the 5 species within the Glyphis family.
Typically, river sharks have a short body shape, wide mouths, and small eyes. They can grow up to 3 meters in length. Additionally, their bodies usually feature wide fins, making them appear more like fish than sharks.
Glyphis Shark
Glyphis shark or Glyphis glyphis is one of the species capable of inhabiting mangrove rivers with strong water currents in northern Australia and New Guinea.
They develop large dorsal fins. Their teeth are embedded deep in the jaw, quite small, and resemble a spear, hence the name “Glyphis Shark.”
According to scientists, Glyphis sharks tend to move with the changing tides to conserve energy. Their daily diet consists of fish and crustaceans. Like many shark species, they give live birth rather than laying eggs.
The International Union for Conservation of Nature (IUCN) has listed Glyphis sharks as a critically endangered species. Currently, there are only about 2,500 Glyphis sharks left worldwide, and their existence is threatened by habitat loss and indiscriminate fishing by humans.
Relatives of the Glyphis shark include the northern river shark, also known as the New Guinea river shark (scientific name: Glyphis garricki), and the Irrawaddy river shark (scientific name: Glyphis siamensis), which was discovered during a river research expedition in the Irrawaddy River in Myanmar in the 19th century.
Ghost Shark
Borneo river shark (scientific name: Glyphis fowlerae) is one of the most famous river shark species discovered in the 19th century.
According to IUCN shark researcher Leonard Compagno, scientific literature regarding the distribution and biological characteristics of river sharks worldwide is very limited. They are like rare “ghosts” that seldom appear and are sparsely distributed. Therefore, the sighting of a river shark is considered a remarkable event.
One of the rare and endangered river shark species is the Ganges river shark (scientific name: Glyphis gangeticus), which primarily inhabits freshwater areas in eastern and northeastern India.
Bull Shark
The Ganges river shark is often confused with the Bull Shark (scientific name: Carcharhinus leucas), as they have similar shapes and structures. They are referred to by various names, including river shark, Zambezi shark, or Nicaragua shark.
In contrast to the danger posed by bull sharks, Ganges river sharks are seldom seen and do not pose a threat to humans.
Bull sharks typically inhabit shallow, warm waters along coastlines and rivers worldwide. They are known for their aggressive hunting behavior and opportunism.
Occasionally, humans may encounter bull sharks far from the shores of Indiana and the Ohio River (USA). They are at the top of the list for shark attacks on humans in coastal areas.
Notably, bull sharks have evolved the ability to thrive in freshwater environments by developing skills to limit salt excretion in the blood through their rectal glands. Their gills and kidneys also help control the absorption and excretion of salt.
Typically, bull sharks hunt alone, but in some cases, they may work in pairs to capture more prey. They mark their territory and are ready to attack any intruders.
