Several dolphin species are found in the waters of Bangladesh. Among them are Irrawaddy dolphins, finless porpoises, Indo-Pacific humpback dolphins, bottlenose dolphins, pantropical spotted dolphins, spinner dolphins, and Ganges river dolphins.
Called "shushuk" in Bangla, Ganges river dolphins are the most well-known dolphin species in Bangladesh. Although their population is dwindling, they are found in the Padma, Jamuna, Meghna, Sangu and Karnaphuli rivers.
Irrawaddy dolphins, as pictured in this story, live in coastal waters where freshwater rivers meet the sea. They are native to South and Southeast Asia.
IUCN listed Irrawaddy dolphins as an Endangered species.
Research at global stage determined that the use of underwater sonar by ships and submarines can interfere with the bio sonar sounds produced by cetaceans (whales, dolphins, and porpoises) and can be fatal for them by affecting their ability to navigate and to locate and catch their food. They can also collide with boat propellers and get killed as a result.
Dolphins feed largely on fish. Traditional wisdom suggests dolphins indicate abundance of fishes around. So fishermen place nets in the water around a pod, and the dolphins get trapped.
Whales and dolphins cannot breathe underwater like fishes can, as the marine mammals do not have gills. They breathe in the air through blowholes. When dolphins surface, they breathe out and inhale fresh air.
When they get entangled in the fishing net, they cannot breathe, and after a while, they die. Some fishermen also reportedly hit the trapped dolphins to free the fishing net.
In some countries like Japan, dolphins are hunted for sport.
Apart from being hunted and killed as bycatch (when they are unintentionally caught in the net with other fishes), dolphins also face threats from habitat loss, and marine pollution.
The dolphins are an important indicator of the health of marine and river ecosystems. Their decline may signal a potentially devastating loss of water quality.