Finless Porpoise

The Finless Porpoise (Neophocaena phoconoides) is one of six porpoise species. In the waters around Japan, at the northern end of its range, it is known as the sunameri. A freshwater population found in the Yangtze River in China is known locally as the jiangzhu or "river pig".

Distribution

The Finless Porpoise lives in the coastal waters of Asia, especially around India, China, Indonesia and Japan. A unique fresh water population is found in the Yangtze River. At the western end, their range includes the length of the western coast of India and continues up into the Persian Gulf. Throughout their range, the porpoises stay in shallow waters (up to 50m), close to the shore, in waters with soft or sandy seabeds. In exceptional cases they have been encountered as far as 100 miles off-shore in the East China and Yellow Seas, albeit still in shallow water.

Physical description

The Finless Porpoise almost completely lacks a dorsal fin. Instead there is a low ridge covered in thick denticulated skin. This demonstrates that the body shape that evolution has chosen as the optimum for sharks, dolphins and porpoises is not the only possible body shape for a marine animal.

Adult Finless porpoises are a uniform light grey colour. Infants are mostly black with grey around the dorsal ridge area, becoming grey after 4-6 months. Adults grow more than 1.55 metres in length. Males become sexually mature at around 4.5 - 9 years of age, females at 3 - 7 years of age. Finless Porpoises eat a wide range of fish, shrimp and cephalopods, consuming whatever is available.

Conservation

There is not enough data to place finless porpoises on the endangered species list, except in China, where they are endangered. Their propensity for staying close to shore places them in great danger from fishing and from population - many Finless Porpoises are killed each year in nets or in lines of hooks (rolling hooks) placed across rivers.

There are no good estimates of the animals' abudance. However a comparison of two surveys, one from the late 1970s and the other from 1999/2000 shows a decline in population and distribution. Scientists believe that this decline has been on-going for decades and that the current population is just a fraction of its historic levels.