Finless Porpoise
From Wikipedia, the free encyclopedia
 |
||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
 |
||||||||||||||||||
|
|
||||||||||||||||||
|
Data deficient
|
||||||||||||||||||
| Scientific classification | ||||||||||||||||||
|
||||||||||||||||||
|
|
||||||||||||||||||
| Neophocaena phoconoides (G. Cuvier, 1829) |
||||||||||||||||||
 Finless Porpoise range
|
The Finless Porpoise (Neophocaena phocaenoides) 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".
Contents |
[edit] 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.
[edit] 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 has evolved to be 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 and up to 30-45 kg (65-100 lb) in weight. 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.
[edit] Conservation
There are 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' abundance. 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. A 2006 expedition estimated that fewer than 400 of animals survived in the Yangtze River [1].
At the end of 2006 it was estimated that there are about 1400 porpoises left living in China, with between 700 and 900 in the Yangtze, with about another 500 in Poyang and Dongting Lakes.
2007 population levels are less than half the 1997 levels, and the population is dropping at a rate of 7.3 per cent per year.
Sand dredging has become a mainstay of local economic development in the last few years, and is an important source of revenue in the region that borders Poyang Lake. But at the same time, high-density dredging projects have been the principal cause of the death of the local wildlife population.
Dredging makes the waters of the lake muddier, and the porpoises cannot see as far as they once could, and have to rely on their highly-developed sonar systems to avoid obstacles look for food. Large ships enter and leave the lake at the rate of two a minute and such a high density of shipping means the porpoises have difficulty hearing their food, and also cannot swim freely from one bank to the other. [2]
[edit] Notes
- ^ http://www.cnn.com/2006/TECH/science/12/13/china.dolphin.ap/index.html
- ^ http://www.chinadialogue.net/article/show/single/en/839-Poyang-Lake-saving-the-finless-porpoise
