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Rescuing Roly-Poly Yangtze 'River Pig'

Dec 20, 2012     Email"> PrintText Size

 
Researchers survey the Shanghai section of Yangtze River while taking notes on the 1,100km survey journey. (Photo by Zhang Suoqing)
 
THE Yangtze River dolphin is extinct and scientists fear the same fate awaits its endangered cousin, the smaller, rounder finless porpoise known as the "river pig." Xu Chi reports.

The endangered porpoise known as the "smiling angel" because of its friendly appearance will probably become extinct in 10 to 15 years if no action is taken to protect its habitat from human threats, according to scientists who are concluding a new 40-day survey.

The finless Yangtze River porpoise, jiang tun (river dolphin), commonly known as the "river pig" (jiang zhu), is rarer than the more numerous giant panda, China's national treasure.

The Yangtze River dolphin, baiji, was declared functionally extinct in 2007. The freshwater dolphin is the only cetacean remaining in the river and its tributaries.

Today the number of finless porpoises is estimated to be around 1,000 in the Yangtze River, its tributaries and two connecting freshwater lakes, Dongting Lake in Hunan Province and Poyang Lake in Jiangxi Province.

In the last similar survey in 2006, the number of porpoises was estimated at around 1,800. This means the freshwater mammal's population is shrinking at an annual rate of more than 5 percent, experts say.

The main reasons for the drastic decline in the population are the increasing number of propeller vessels in the river, lakes and tributaries; sand dredging and destruction of habitat; lack of food for porpoises from overfishing; illegal fishing, including use of electrified nets in which porpoises get caught; and toxic water pollution caused by the expansion of heavy industries, experts says.

Porpoises are smaller and rounder than dolphins, with rounder, blunt snouts and spade-shaped teeth. The word porpoise comes from the Latin word porcopiscus - porcus meaning pig and piscus meaning fish.

Starting on November 11, researchers surveyed a 1,100-kilometer-long section of the Yangtze River between the city of Wuhan and Shanghai at the mouth of the Yangtze River. They spotted only 177 porpoises, says Wang Kexiong, associate researcher at the Institute of Hydrobiology of the Chinese Academy of Sciences.

The actual number of porpoises may actually be lower than those spotted because there may have been multiple sightings, Wang told reporters last Wednesday as his survey team arrived in Shanghai.

The team is now traveling back to Wuhan from Shanghai, a distance of around 1,700 kilometers, in the second and final leg of the survey. They are continuing to count.

The team includes scientists and researchers from the Ministry of Agriculture, the Chinese Academy of Sciences and the World Wildlife Fund.

They counted using two boats and observing from 7am to 5pm; they also use sonar equipment to collect sound traces of the porpoises.

"We are still collecting data to calculate the number of porpoises left in the Yangtze River, but apparently the number has fallen dramatically since the 2006 survey," Wang says.

To illustrate his point, Wang says the team did not spot a single porpoise at the mouth of the Yangtze River in Shanghai, while in 2006 they spotted one. In Dongting Lake, which is linked to the waterway, the team found less than 100 porpoises, compared with 150 six years ago.

The number of unnatural fatalities is on the rise. Usually 20 to 30 of the mammals are found dead every year - killed by propellers, starved for lack of food, electrocuted by fishermen or sickened by pollution - but more than 30 have been found dead in the first six months of this year, Wang says.

In Dongting Lake alone, 12 porpoises have died this year. Last month, the team spotted a dead porpoise whose head was mutilated by a ship's propeller, according to Wang.

"Most of the porpoises died in accidents with ships, or they died because of fishing, getting stranded and poisoning from severe water pollution," the researcher says.

The survey found that many porpoises fled the main river channel to escape from expanding shipping and moved into tributaries. "As a result, the porpoises are dived into small and scattered groups, making it harder for them to mate and bear offspring,"

In the river section between Wuhan and Shanghai, the team spotted 3,743 cargo vessels and 276 fishing boats. In a busy river section where they spotted 88 cargo vessels in 30 minutes, they only spotted 13 porpoises, compared with 40 sighted in the same section in the 2006 survey, according to Wang.

Vessels pose extreme danger because of the sounds made by engines and propellers, which confuse porpoises and affect their vocalizing and biosonar, he says.

Porpoises use their biosonar system to detect danger, navigate, hunt for food and communicate with others. They emit sounds, listen to the echoes and use them to identify objects.

To communicate with their mothers, porpoise calves emit sounds that are similar in frequencies to those of ships' engines and propellers. But their inability to distinguish can send them toward deadly propellers, especially during the first year of life.

Meantime, the team also found fishermen who were fishing illegally late at night by using electrified nets. Although they are not targeting porpoises, some mammals die while swimming into the nets.

"These porpoises are at the top of the food chain in the Yangtze River ecosystem and they don't have any natural enemies, except for man," says researcher professor Wang Ding from the Institute of Hydrobiology.

"The number of porpoises and their living conditions are strong indicators of the status of the river and now they are facing extinction, which means the river environment has deteriorated rapidly and may not support other life in the future," he says.

The survey also indicated that the number of fish - food for the porpoise - has also decreased dramatically because of the degraded environment and illegal fishing.

"If we human want to save the porpoises, we have to reduce the number of ships and the speed of vessels on the river," says associate researcher Wang Kexiong, "This means we need to press for the drafting of a sailing law."

"Vessels can navigate freely on the river, as well as in some freshwater porpoise protection regions, since there is no law to regulate their speed," he adds.

In some porpoise protection areas, local governments have approved transport-related projects that should have been denied, but they bribed higher officials to smooth the way, Wang says.

One proposal is that vessels in porpoise protection areas should be guided into one channel, while porpoises should be in another," he says.

Porpoises are categorized as class-2 endangered animals in China. Categorizing them in class-1, like the giant panda, would theoretically provide greater protection by making more funds and resources available, and punishing those who kill and endanger them. (Shanghai Daily)


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