ISLAMABAD - Indus river dolphin is the world’s rarest mammal. It is one of four species of dolphin that spend all their lives in freshwater. It is the second most endangered freshwater dolphins in the world.
Indus river dolphin is originated in Tethys Sea. It is declared endangered by the IUCN red list status. Their weight is 155-245 pounds and length is 8.2 feet. They are characterised by their long beaks, rounded belly, stocky body, very small dorsal fin and large flippers. This species is also referred to as the ‘blind dolphin’ as its eyes have not developed a lens. It relies on echolocation to find fish, shrimp, and other prey in the bottom mud.
The Indus River dolphin swims on its side, at times enabling it to move in water as shallow as 30 cm. As it swims on its side, it trails a flipper along the bottom of the river.
After 30 to 60 seconds, when it needs to breath, it swims to the surface, rotates upright to take in the air, and then rotates 90 degrees again as it swims back to the bottom. This unique side swimming behaviour is not consistently seen in any other dolphin, except the Ganges River dolphin.
Initially, their population declined as the sea dried up approximately 500 million years ago. They were forced to adapt other habitat, i.e. river.
They extinct due to the loss of their habitat as most of the irrigation system are constructed and they live in muddy water which results in functionally blind dolphins.
Indus dolphins were sought and killed for oil until early 1970s. In addition, some communities who rely heavily on fishing consider that they are competing with Indus River dolphins for fish.
Now they are only 1,816 left which are found in lower parts of Indus river of Pakistan so they are called Indus river dolphin.
The Indus river dolphin matters because it is important health indicator of river and is found only in Pakistan.
The main reason for extinction of Indus river dolphin is the construction of rivers and barrages which split their population in small groups and ultimately which caused decline in their number and the other reason is that the fishing nets are set for many hours and dolphins get trapped in nets and get drown this accidental capture of dolphin is known as by-catch.
The untreated sewage from the communities and the industrial area goes directly into river which causes water pollution and the chemicals from the industries which are untreated go to river bank and make the water acidic which directly affects food supply of Indus river dolphins and result in reduced number of dolphins and the habitat fragmentation due to construction of barrages is major reason behind dolphins move downstream of Indus river and then they are unable to move upstream due to strong water currents .
The irrigation canals are extended in the river and the Indus river dolphin goes to canals and ultimately dies without being rescued.
Organisations like WWF are working hard for the population growth of Indus river dolphin by spreading radio tags which tell the movement of Indus river dolphin so they could keep a check on the movement of Indus river dolphin and if in case they are in danger, they can easily be rescued.