In the sea area of east China's Xiamen bay, two white and gray figures swim happily with frequent floating, rolling, and jumping.

"Look! The white one is Dabai, and the gray one is her baby. She is playing with her baby," said Wang Xianyan, a researcher at the Xiamen-based Third Institute of Oceanography, Ministry of Natural Resources, as he showed a video on his mobile phone.

Dabai is a Chinese white dolphin living in Xiamen bay. The mammal is guarded under the first-class state protection in China and is included on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species in 2008.

According to Wang, despite being called the "white dolphin," the newborn calves are grey.

Wang took the video this April. As a researcher in the field of Chinese white dolphins for more than a decade, he has filmed countless videos and pictures of the dolphins.

"There are about 60 to 70 white dolphins in Xiamen bay. It's not rare to see a few heads of white dolphins while walking on the shore. People living at the seaside often see white dolphins from their balconies," Wang said.

In Xiamen bay, the living environment of white dolphins highly overlaps with the range of human activities. Xiamen is the only city in China where people are able to see inshore dolphins on its beaches. In other provinces and regions, such as Guangdong and Guangxi, people can only get to dolphins in the open sea after hours by boat.

Protecting the white dolphins takes decades of persistence and dedication.

According to Cai Libo, director of the Xiamen Chinese White Dolphin Amphioxus Nature Reserve Affairs Center, the provincial white dolphin reserve was set up in Xiamen to lure back the rare mammals in 1997. In 2000, it was upgraded to a national-level nature reserve for rare marine species, covering a total area of 7,588 hectares.

In addition to designating protected areas, supporting measures have been timely followed up. In 2001, the construction plan of the national reserve and special protection plan for Chinese white dolphins were formulated and implemented. The reserve authorities also took the lead in compiling and organizing the implementation of the national action plan for Chinese white dolphins.

Measures including fishing bans were also adopted to reduce the impact of human activities on dolphins. Ecological measures such as the restoration of mangrove wetlands have expanded the living space of white dolphins.

"White dolphins are the top predators in an ecosystem and an indicator species of ecosystem health. In Xiamen bay, an area of high human activity, the white dolphin population is stable and increasing, which indicates that the ecosystem here is relatively healthy," Wang said.