Unlike other shark species, river sharks are found in rivers rather than the ocean. Because they reside in freshwater rather than saltwater, they are not like the sharks you see in movies. Scientists continue to learn fascinating things about river sharks. Their distinct characteristics and habits enable them to thrive in their freshwater habitats. River sharks are endangered by human activity, despite their significance to freshwater ecosystems. It’s critical to learn more about these creatures in order to safeguard both the intriguing creatures and the waterways that sustain them.
About the River Shark
The tropical river shark is found on the floor or bottom of mangroves. The Eastern Indian Ocean is home to the Irrawaddy river shark. It is located in and around the Irrawaddy River, which flows north to south across Myanmar (Burma) and is one of the largest and most significant commercial waterways in the nation. Because its habitat is being destroyed for fuel, building materials, and non-timber forest products, this shark species has been designated as critically endangered. Concerns about artisanal fishing and habitat pollution also pose a threat to the population of this endangered species.
The River Shark is a thick-bodied, plain gray shark with small eyes, a short, rounded snout, and a large dorsal fin at the top. There are 29 tooth rows in the upper and lower jaws of the large mouth. Live young are born to females. The Irrawaddy river shark’s short teeth indicate that smaller fish are its primary food source.
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Physical Characteristics
Because they evolved to live in freshwater habitats, river sharks have unique physical traits that are appropriate for their environment. They usually have fusiform forms and streamlined bodies that let them move quickly across river currents. Frequently extended, their dorsal fins provide stability during swift motions and aid in their efficient maneuvering in choppy waters. Furthermore, river sharks have powerful jaws with sharp teeth, which allows them to hunt a variety of aquatic prey. Their sensory organs, like their strong electroreception and sharp eyesight, are well adapted for seeing prey and navigating the murky river conditions. The combination of these physical adaptations demonstrates river sharks’ exceptional evolutionary adaptations to riverine habitats, enabling them to flourish as apex predators in their freshwater ecosystems.
Distribution and habitat
Although their exact geographic range is unknown, the recognized species have been found in Australia, South Asia, Southeast Asia, New Guinea, and parts of Africa [5]. Science now recognizes three species: the northern river shark and speartooth shark inhabit coastal marine waters, while the Ganges shark exclusively inhabits freshwater. Despite occasional confusion between the bull shark (Carcharhinus leucas) and the river sharks of the genus Glyphis, it’s crucial to distinguish between them. While other sharks may thrive in saltwater, river sharks have evolved to give birth to their young in freshwater, making them safe to roam in the water.
Conservation
Together with Indigenous communities, the Marine Biodiversity Hub of the National Environmental Science Program is working to better understand these uncommon sharks and how to conserve them. The multispecies recovery strategy of the Australian government, which includes initiatives to increase the population of these endangered sharks, is informed by the research.
Biology
Within the family Carcharhinid, there are potentially four or five species of Glyphic, of which Glyphic glyphic and Glyphic Garrick are two. These medium-sized whale sharks have small, gray eyes, a short, broadly rounded snout, and upright, roughly triangular, serrated upper teeth. They lack a recognizable color pattern (Last & Stevens, 1994).
The Glyphic sharks’ narrow teeth and small eyes indicate that they are predominantly carnivores that have adapted to hunting in murky river and estuary waters. These species may reach a maximum length of two to three meters, while their exact size is unclear (Last & Stevens, 1994). The bull shark, Carcharhinids leucas, can be readily confused with Glyphic glyphic and Glyphic Garrick because all three species share a similar habitat and may even inhabit comparable ranges at different phases of their life cycles. But compared to bull sharks, glyphic appear to be more suited to low-oxygen habitats (Last, pers comm).
Threats and Conservation Status
River sharks’ existence is threatened by a variety of factors, which adds to their precarious conservation status. Deforestation, pollution, and dam construction are among the human-caused habitat degradation activities that cause these animals’ freshwater ecosystems to be disrupted and their populations of available prey to decline. Overfishing is a serious issue as fishing gear frequently unintentionally captures river sharks or targets them for their fins and meat. In addition, habitat fragmentation prevents individuals from moving freely and from exchanging genetic material with other populations, which lowers genetic diversity and makes populations more susceptible to environmental changes. Conservation measures, such as habitat restoration programs, protected area creation, and fishing practice regulation, are in progress despite these obstacles. Raising awareness of the value of protecting river shark populations and their ecosystems—and emphasizing the pressing need for coordinated action to preserve the long-term survival of these mysterious species—also depends on collaborative research and community participation.
Human interactions
It seems that there are very few subpopulations of the northern river shark in Australia and Papua New Guinea, although there might yet be more of them. Information available suggests that there are no more than 250 mature individuals in the wild, with no more than 50 in any one subpopulation. [1] Both commercial and recreational fishermen use longlines and gillnets to catch this species, which is also legally and illegally harvested; habitat deterioration could be another threat to the species’ existence. The northern river shark has been classified as vulnerable by the IUCN due to its low natural abundance, restricted distribution, strict habitat needs, and vulnerability to a variety of stressors induced by humans. The 2000 Territory Parks and Wildlife Conservation Act and the 1999 Commonwealth Environment Protection and Biodiversity Conservation Act also classify it as endangered.
Research and Scientific Studies
Because of their elusiveness and distant locations, river sharks have not been the subject of much scientific research. On the other hand, new research has sought to unearth vital details regarding their behavior, ecology, and population dynamics. Researchers have learned more about the movements, migratory patterns, and genetic diversity of different river shark species through methods like acoustic telemetry, genetic analysis, and ecological modeling. The findings of these studies greatly influence conservation policies and management initiatives to protect these threatened apex predators and their freshwater habitats. The long-term survival of this rare and ecologically significant species depends on ongoing research into the biology and ecology of river sharks.