River shark

River sharks are requiem sharks in the genus Glyphis, with species living in rivers and coastal waters of the Indo-Pacific. They are rare, poorly known, and threatened by habitat loss and fishing.

Glyphis: A genus of requiem sharks adapted to river and coastal habitats in the Indo-Pacific. River shark names the genus itself; its species differ in range and conservation status.
Speartooth shark: A rare Glyphis species found in rivers and estuaries of northern Australia and southern Papua New Guinea. It is one of the best-known river sharks and has a restricted range.
Freshwater adaptation: Physiological or anatomical traits that allow organisms to live in low-salinity environments. River sharks must balance water and salts differently from sharks restricted to seawater.
Shark population assessment: The estimation of shark abundance, demographic structure, and population trends. Rare encounters make reliable population estimates especially difficult for Glyphis.
Requiem shark: A family of mostly migratory sharks that includes many familiar coastal and open-water species. Glyphis belongs to this broader shark group despite its unusual river habitats.
Ganges shark: A critically endangered Glyphis species known from the Ganges–Hooghly river system in India and Bangladesh. Its river-basin range illustrates the genus's association with large tropical rivers.
Osmoregulation: The regulation of water and dissolved-ion concentrations within an organism. It is the physiological challenge underlying movement between freshwater and seawater.
Environmental DNA: Genetic material organisms shed into water, soil, or air and that can be sampled to detect their presence. Water samples may reveal river-shark presence where direct sightings are scarce.
Carcharhinidae: The family of requiem sharks, characterized by typical placoid scales and two dorsal fins. This family classification places Glyphis among the requiem sharks.
Irrawaddy river shark: A poorly known Glyphis species described from the Irrawaddy River in Myanmar. Its identification rests on a limited specimen record from a major river.

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Bull sharkCompared with: Unlike these specialized river sharks, bull sharks are large coastal sharks that also enter rivers.