Yangtze River Dolphin (Baiji)

The baiji is also called Yangtze River Dolphin,is a graceful animal, with a long, narrow and slightly upturned beak and a flexible neck. As opposed to some other freshwater dolphins, like the Indus River dolphin, its eyes are functional, although greatly reduced. Its coloration is bluish-gray to gray above and white to ashy-white below. It weighs 135 - 230 kg (300 - 510 lb) and measures as much as 2.5 m (8.2') in length.
The baiji only occurs in freshwater rivers and lakes. It favors large eddy counter-currents such as are found below meanders; channel convergences; and areas in a river with structure, such as sandbars. In the Yangtze River, the baiji generally lives in the deeper sections, swimming to shallow water only to catch small fish. Any available species of small (less than 6.5 cm (2.5") in width) freshwater fish is eaten. Feeding activity is primarily diurnal.

A group may congregate in the quiet area of an eddy for 5 - 6 hours. At night the baiji often rests in areas of very slow current. Several underwater acoustic signals are apparently used for communication and echolocation. Baijis generally live in small groups of 3 - 4 animals, which may come together to make up a larger social unit of 9 - 16 dolphins.
The distribution of the baiji originally included not only the lower and middle reaches of the Yangtze River down to the river’s mouth, but also the Qiantang and Fuchun Rivers and Dongting and Poyang Lakes. It no longer occurs in the lakes or branches of the Yangtze but only in the mainstem, and the extent of its distribution is significantly reduced. The baiji is considered the most endangered cetacean, and its prospects for survival are extremely doubtful.
Deaths from entanglement in or electrocution by fishing gear, collisions with vessels, blasting for channel maintenance, and illegal harvesting of the baiji are at least partially responsible for the decline of its range and abundance. In addition, the damming of tributaries, drainage for land "reclamation," dredging, depletion of the baiji's prey by over-fishing, and noise and congestion caused by vessel traffic in the river have substantially degraded the Yangtze's environment. The Three Gorges Dam will produce further stress on the baiji population by altering the Yangtze's hydrological regime. The baiji generally occurs in large eddy counter-currents which are expected to be eliminated for approximately 200 km (120 mi) downstream by the water released below the dam.