Fisherman Shu Yin'an remembers he was often woken up by the sounds of finless porpoises at night when he was young, but the animal, peculiar to China's Yangtze River, is hardly seen now.

Finless porpoises are a freshwater animal and the only water mammal in the Yangtze river. Around 1,000 finless porpoises are believed to live in the Yangtze and two lakes linked to the busy waterway.

In 1991, there were around 2,700 porpoises. By 2006, the number had dropped to 1,800 and the population has since declined further. Without effective protection, the porpoise may be extinct within 10 years.

Shu Yin'an, who lives where the Yangtze meets Poyang Lake, has joined with another ten, mostly retired, fishermen to form a squad to protect the species.

"When I was young, I once met a porpoise the size of a long wooden boat. When I slept on the boat at night, I was often woken up by noise the animals made. It is sad that there are so few of them now," Shu said.

Along the banks of Yangtze, local saying goes: "when the river pigs (porpoises) jump, the tide will be high." The appearance of porpoises on the surface often meant the air pressure was low and storm was coming.

"For so many years, I was a fish saboteur, and now I have to pay back," said squad leader Zhang Chuanguo, 65.

"We once used large trawls and sharp hooks. I saw dead porpoises a couple of times. They died from wounds by fish jigs," said Zhang, who volunteered to join the squad last year.

Along the Yangtze, there are forty wardens tasked specifically with protection of porpoises and the number is expected to reach 100 in July. They use an app called "Porpoise Wardens." They take pictures of any animals they see, upload the pictures, record injuries and report any activities that may threaten the environment such as illegal dredging, fishing and discharge of sewerage.

Each squad completes five patrols each week and covering 40 kilometers of river every day.

On March 14, Zhou Junqi, 63, found a dying porpoise in Poyang Lake.

"It was motionless when we discovered it. We hauled it up to the boat and found a baby porpoise under the mother's belly. There was nothing that I could do, and it was something that I can never forget," he said.

Patrollers confiscate any illegal fishing equipment they find. "Some fishermen know me and do not understand what I do now. They say: you were once a fisherman too, and now you take away some else's tools?" said Shu Yin'an.

"I tell them about law and new regulations and the importance of not to making money at the expense of mother nature. I tell them to think about what it means for the future generation if the environment gets worse," he said.

In 2016, then Ministry of Agriculture announced a Yangtze River Finless Porpoises Rescue Action Plan (2016-2025).