The Indus River Delta is a highly productive ecoregion at the juncture of both freshwater and marine systems. It has a rich freshwater fauna and is an important area for migrating water birds.
Melting snow and glacier ice in the Himalayan Mountains pour into the Indus River, which picks up speed as it heads through Pakistan. Throughout its 1,900 mile (3,000 km) course, the Indus provides mineral-rich soil and water to its floodplains. Both the Indus and the streams that feed it are home to many types of unusual fish and other animals.
Heavy rains swell the Indus River during the monsoon season from June to September. Because this happens soon after the winter snows melt, floods can occur at this time of year. For a long distance, the river is a wide channel of cloudy water twisting through a dry landscape. Before it pours into the Arabian Sea, the Indus creates a wide delta of swamps, streams, and extensive mangroves.
Many fish species live in or migrate through the waters of the Indus River Delta. The Hilsa shad swims up from the Arabian Sea to spawn in freshwater. This fast swimmer has been clocked at 43 miles (71 km) per day. Other unusual fish that live in the Indus include the Indus baril, Indus garua (a catfish), and the Rita catfish. Several snakehead fish also live here, including the giant snakehead, which can grow to be 6 feet (2 m) long and eats fish, frogs, snakes, insects, and earthworms. There are even reports that it will occasionally eat a water bird! Species that are important to people as food, such as the golden mahaseer and large freshwater shrimp, are part of the abundant aquatic life of the delta. But the most unusual member of the ecoregion is the endangered Indus River dolphin, one of four species of freshwater dolphin in the world.
Cause for Concern
Dams on the river reduce flows in lower portions of the system and limit the transport of fertile sediments downstream into the delta. They pose a serious threat to the survival of the Indus River dolphin, as the remaining individuals become isolated into smaller groups. Water extraction for irrigation and run-off of chemicals into the rivers also threaten the freshwater species of the Indus Delta. Introduced species may pose a problem for the native fauna, too.