WUHAN -- Four finless porpoises from Poyang Lake in East China's Jiangxi province have been relocated to waters in a nature reserve in Hubei province.

The four finless porpoises, two males and two females, were transferred Monday to Hewangmiao nature reserve along traffic-free sections of the Yangtze River in Hubei, according to sources with the Institute of Hydrobiology, the Chinese Academy of Sciences.

The reserve has a vast body of water, which is clean and rich in aquatic bio diversity due to limitations on fishing, the sources said.

A project was launched in 2017 by the Ministry of Agriculture, the Chinese Academy of Sciences and three provincial governments to relocate 22 porpoises, which are facing extinction, this year.

"Our plan is to move them to areas free from human activities, so they can flourish," said Wang Ding, a porpoise expert.

The finless porpoises, known for their "grins," live in the Yangtze River and two lakes linked to the busy waterway.

There are only around 1,000 porpoises left as their natural habitat is threatened by pollution, over fishing and river traffic.

China started a porpoise relocation program in 1992 after concerns were raised that the population of the species had shrunk by an average of 13.7 percent every year despite preservation measures.

"At first, the relocation was floated to protect the Yangtz River Dolphin, but they were 'functionally extinct' before we acted," said Wang Kexiong, a researcher with the Chinese Academy of Sciences.

China has established three finless porpoise nature reserves in Hubei, Hunan and Anhui provinces.

"It has been an effective measure. We have recorded three to five births each year. Tian'ezhou reserve in Anhui has already had more than 70 porpoises," Wang Ding said.

There are plans for more in the middle and lower reaches of the river.

The Yangtze, China's longest waterway, is known for its aquatic bio diversity. A decade ago, it was the only river in the world that had two kinds of aquatic mammal living in it at the same time -- the finless porpoise and the white-flag dolphin.

However, a 2006 survey found no white-flag dolphins in the river, suggesting they were "functionally extinct," which means the population is too small for the species to reproduce.

Scientists predict that without efficient protection the finless porpoise will also disappear in five to ten years.

Wang said an overemphasis on the Yangtze's economic value and the ignorance of its natural attributes has resulted in the deterioration of habitat for the river's endangered species.

Many porpoises have been found wounded or dead as a result of starvation, pollution-induced disease or injuries inflicted by ship propellers.

In 2016, China released a guideline to increase traffic along the Yangtze, part of efforts to build an economic belt along the river. It emphasized that development should not be at the cost of environmental protection measures.

"We are working on more comprehensive measures to protect the environment along the Yangtze River," said Li Yanliang, a Ministry of Agriculture official.