In July 2016, Yu Yongguang saw a Yangtze finless porpoise for the first time in a newspaper, and he found himself fascinated by the "smile" of the calf porpoise that had been saved by a fisherman.

Two months later, Yu, who was working as a teacher at the Jiangsu University of Science and Technology in Zhenjiang, Jiangsu province, established an on-campus association to protect the critically endangered mammal. At first, there were only seven members.

"At the very beginning, I was just fascinated by that 'smile'. After reading more about the animal, I learned that it is an 'indicator species', whose health has far-reaching importance for the Yangtze River's ecosystem and even beyond," the 40-year-old said.

Yu now works as a secretary for the committee of the Communist Youth League of China at the university's School of Environmental and Chemical Engineering.

In recent years, his perseverance has paid off, and the association he founded now has about 750 members. Moreover, thanks to close cooperation with universities, government bodies and nonprofit organizations, the association has mobilized about 8,000 volunteers across the Yangtze River Basin to contribute to the cute mammal's protection.

This year, Yu was selected as one of China's 100 model environmental protection volunteers.

"In the early days, we mainly rolled out publicity activities in primary schools and residential communities to improve awareness of the Yangtze finless porpoise and environmental protection," he recalled.

To date, his team has organized more than 300 publicity activities in 16 major cities in five provincial regions across the river basin, traveling 15,000 kilometers in total.

As his association has developed, its work has gone far beyond organizing mere publicity activities.

Under Yu's leadership, his team members compiled the country's first popular science book on the finless porpoise. They have also devised various designs for a science popularization curriculum targeting different groups of people.

The team has also developed an app that incorporates science popularization with exchange and training programs on the conservation of the aquatic mammal.

Employing a cross-university group established by the association to advocate for the mammal's protection, it mobilized students from 12 schools in six provincial regions within the river basin to participate in the endeavors.

Yu said he never imagined that the small association he founded would unite so many forces to protect the animal that is often dubbed China's "smiling angel".

In addition to organizing summer and winter camps that allow university students to visit the major habitats of the porpoise, he has led his team to those fertile areas to conduct scientific investigations and environmental monitoring.

Based on this work, the team has compiled a series of reports that include research-based suggestions on improving the habitat preservation work. The scientific investigation is conducted every five years.

Currently, the number of Yangtze finless porpoises is stable and stands at around 1,000, Yu said.

He has pledged consistent work by himself and his team to safeguard "the porpoise's smile" and "the vitality of the Yangtze".

"President Xi Jinping once said that our generation must not allow the ecological environment of the Yangtze River to continue to deteriorate, and that we must leave our descendants a clean and beautiful Yangtze River," he said.

"Inspired by those words, I will continue to work on the front line of conservation of the Yangtze finless porpoise and the river."

He said he believes that the consistent endeavors of different sectors of society will see the number of finless porpoises continue to rise, and will also help the environment around the Yangtze basin to improve continually.