Anqing in Anhui province has seen a significant increase in the number of critically endangered Yangtze finless porpoises following its endeavor to rectify violations that jeopardized habitats of the mammal, which is known in China as the "water panda" because of its rarity.

There are now 180 to 200 such porpoises in the Anqing section of the Yangtze River, up from the 130 to 150 counted in 2015, according to the local department of ecology and environment.

In a video shot by a vessel owner passing by Anqing along the Yangtze that went viral on the internet last year, five of the mammals showed up and occasionally jumped out of the water, including a calf.

"What a big group of river pigs. I thought there must be over 10 of them. Not afraid of us, they were swimming just a stone's throw away from me," the veteran vessel runner was quoted by local media as saying. "I have not seen them for more than a decade."

The porpoise is called a river pig in many areas in southern China.

The change has come about after the city was rebuked by the high-profile central environmental inspection in 2018 for unapproved changes to a safe zone for the mammal that was set up in Anqing in 2007. Stretching for 806 square kilometers, the zone covered the entire main stream of the Yangtze that runs through the city.

In a monthlong visit to Anhui, however, inspectors found that, without approval from provincial authorities, the local government had adjusted the zone's size and downgraded the protection level in some areas to allow activities that threaten the porpoise.

A 2015 document from the Anqing government, for example, reduced the safe zone to 552 sq km and left it covering only part of the Yangtze's main stream, according to a circular from the Ministry of Ecology and Environment, where the office of the inspection is based.

Staffed by officials from the ministry, teams with the inspection are usually led by ministerial-level officials and report to a central group headed by Vice-Premier Han Zheng.

A 91-km Yangtze section excluded from the protected area threatened the survival of about 50 Yangtze finless porpoises, the circular said.

The protection levels of two foraging areas were downgraded in 2016, and a year later the areas were removed from the zone altogether, inspectors found. More than 10 wharves, including one handling hazardous chemicals, were set up along a 2-km section of the Yangtze between the foraging areas.

None of the changes, however, went through necessary procedures as required by a 2010 guideline on natural reserves issued by the State Council, the country's Cabinet. The document states that approval from provincial-level governments is needed to make such adjustments, and the adjustments should be recorded with the ministry.

According to the Anhui department of ecology and environment, it rolled out classified measures to rectify violations at all of the 121 wharves along the section of the Yangtze in the city. While 53 of them were upgraded, the other 68 were shut down, returning 37 km of shoreline to the Yangtze.

Seven of the total 18 sewage outlets that discharge into the Yangtze in the city were removed, it said. All wastewater disposal plants in urban Anqing were asked to treat sewage in accordance with the highest national standard.

The city enacted a regulation on protecting the porpoise in 2020.Approved by the Anhui government early last year, Anqing set up an almost 400-sq-km protected area for the Yangtze finless porpoise. "It is currently the largest protected area for the mammal," the department said.