Chinese ecological wisdom powers Yangtze revival

WUHAN, Aug. 9 (Xinhua) -- To many Chinese, the Chishui River stirs memories of the Red Army's epic crossing during the Long March or the rich aroma of Moutai it has nurtured, but to fish ecologists, it is a living vault of ecological mysteries.

As the only major tributary in the upper reaches of the Yangtze River that still flows freely, the Chishui River has become a vital sanctuary and breeding ground for rare and endemic fish. Chinese scientists are using it as a natural laboratory to conduct research aimed at reviving the ecology of the Yangtze, China's longest river.

SANCTUARY FOR RARE FISH

Flowing through Yunnan, Guizhou and Sichuan provinces in southwest China, the Chishui River runs freely, undammed along its main course.

Since the 1990s, researchers from the Institute of Hydrobiology (IHB) of the Chinese Academy of Sciences (CAS) have been stationed along its banks, surveying, monitoring and breeding fish. Their work has yielded an unrivalled chronicle of the river's biodiversity.

More than 160 fish species inhabit the Chishui, over 40 of which are rare and endemic to the upper Yangtze. With the hydropower development along the Yangtze's main stem and many of its large tributaries, the Chishui River's role as a "refuge" for rare fish has become increasingly vital.

Liu Fei, born in 1984 far from any great river, first joined an IHB research team on the Chishui as a senior university student in 2008. That experience changed him, sparking a lifelong commitment to protecting the Yangtze. Today, as an associate researcher at IHB, he has spent 17 years conducting continuous scientific monitoring along the Chishui's free-flowing waters.

The monitoring data from Liu's first decade in the field painted a sobering picture. Compared to historical records, large and medium-sized fish were shrinking from the catch, while populations of some endemic species were declining year after year.

Following strong appeals from scientists, a "10-year fishing ban" was implemented on the Chishui River starting January 1, 2017.

The impact was immediate. Catch per unit effort nearly tripled, biomass surged, and the ecosystem grew in maturity and stability. Rare species increased from seven to nine, while 11 species, including the Yangtze sturgeon and eel, reappeared after years of absence, according to Liu Huanzhang, director of the IHB's Aquatic Biodiversity Conservation and Utilization Laboratory and head of the Chishui River research station.

The fishing ban was just the first step. Unregulated small hydropower stations on the Chishui's tributaries had once caused riverbeds to dry up and habitats to fragment. In 2020, a "dam removal campaign" was launched.

Liu Fei's team inspected 373 small dams one by one, prioritizing removals based on the ecological needs of rare fish and local demands for drinking water and irrigation.

By the end of 2024, over 320 small dams had been dismantled. In addition, researchers and conservation authorities adopted nature-like restoration techniques to create diverse habitats for fish with different ecological requirements.

For species like the Yangtze sturgeon, recovery remained slow. Relying on the river's excellent water quality, the team conducted natural breeding experiments.

"Since around 2000, no natural reproduction of the Yangtze sturgeons had been recorded," Liu said.

"We modified the Chishui's natural riverbed, and in April this year, the sturgeons finally spawned and hatched successfully. This marks a critical step toward restoring their wild population," Liu added.

Liu Huanzhang said that the Yangtze sturgeon experiment also provided valuable insights for the assisted reproduction of more endangered species, like the Chinese sturgeon and other species.

RECUPERATING YANGTZE

The Chishui's comprehensive, long-term datasets, breeding experiments and fluvial-ecology insights now underpin restoration strategies for the entire Yangtze.

Hu Wei, deputy director of IHB, pointed out that since the turn of the century, the Yangtze's ecological environment has deteriorated sharply. Rare aquatic species like the Baiji dolphin and Chinese paddlefish have been declared functionally extinct, while the Chinese sturgeon and finless porpoise are critically endangered. Populations of the four major domestic fish have also declined drastically.

IHB-led surveys of the Yangtze finless porpoise show its numbers plummeted from about 1,800 in 2006 to just 1,000 in 2012, making it even rarer than the giant panda. Without timely and effective conservation measures, the species could vanish from the wild within 15 years. Overfishing is the primary culprit, Hu said.

As early as 2006, CAS academician Cao Wenxuan, with the IHB, first called for a 10-year fishing ban for the Yangtze, a pivotal policy that later materialized.

Liu Huanzhang explained that the traditional three or four-month seasonal bans only postponed inevitable overfishing once they ended. A decade-long ban, covering two to three generations of key species, provides a real opportunity for lasting recovery.

On January 1, 2020, the Yangtze River 10-year fishing ban took effect.

IHB established 10 field stations covering key Yangtze habitats. It also maintains the longest and most comprehensive aquatic biodiversity database for the river, and has developed advanced smart monitoring systems.

Hu noted that the fishing ban has now reached a crucial midpoint. Monitoring data from 2021 to 2024 recorded 344 native fish species in the Yangtze basin, 36 more than before the ban. In the Yichang section of the middle Yangtze, the spawning biomass of four major native fish species has nearly doubled each year, rising 1.97-fold annually.

SAVING "GIANT PANDA OF THE WATER"

In an aquarium named after the Baiji dolphin at IHB in Wuhan, capital of central China's Hubei Province, visitors can only see preserved specimens of the Baiji, a species declared functionally extinct in 2007, leaving a deep regret felt by people worldwide.

"The Yangtze was once home to two cetacean species: the Baiji and the Yangtze finless porpoise. Now, this facility is dedicated to protecting the latter," explained Zheng Jinsong, head of IHB's cetacean conservation biology research group.

The Yangtze finless porpoise, dubbed the "giant panda of the water," is the ecological barometer of the Yangtze and its population mirrors the health of the river.

Wang Kexiong, a researcher with IHB's cetacean conservation biology group, recalled, "In the 1990s, Yangtze finless porpoises were still common, and our attention was focused on the Baiji. But by 2006, their numbers had plummeted, falling to just 1,012 by 2017. Sand mining, illegal fishing, pollution, heavy shipping and habitat loss were the main culprits."

Facing this crisis, IHB established an integrated protection system combining in-situ conservation, ex-situ conservation and captive breeding research.

Zheng noted that the aquarium currently houses 12 finless porpoises, five of which were born in captivity, including second-generation births. New calves arrive almost every other year since 2018.

Ten nature reserves protect the species in the wild, supported by regular monitoring and targeted habitat restoration.

"China conducts a finless porpoise population survey every five years. The 2022 survey recorded 1,249, increasing over 200 since 2017. This marks the first recorded increase, a historic milestone. This rebound would have been impossible without the 10-year fishing ban," Wang said.

As early as the 1980s, witnessing the Yangtze's ecological decline, Chinese scientists feared the finless porpoise might follow the Baiji into extinction. They proposed an innovative approach of ex-situ conservation in the Yangtze oxbow lakes, which are old river channels formed by natural course changes. Although met with skepticism internationally because no successful precedent existed for cetacean ex-situ conservation, Chinese scientists persisted and ultimately succeeded.

Of the four ex-situ conservation sites, the Tian'ezhou oxbow in Shishou, Hubei Province, stands out. This lake, formed by a Yangtze course shift, has seen its porpoise population grow from four in 1996 to about 100 in 2021.

As ex-situ populations thrived and approached their environmental capacity, scientists began a new effort to reintroduce them into the Yangtze's mainstream.

"With the Yangtze's improving environment and recovering fish stocks, we're confident about returning ex-situ finless porpoises to their natural home. They belong in the Yangtze," Wang said.

Scientists chose Laowan, an oxbow in the Xinluo section of the Yangtze, as China's first finless porpoise rewilding base.

"Ex-situ conservation sites resemble lakes with calm waters, but the water flow in the Yangtze is complex. Laowan's seasonal water level changes mimic the Yangtze's main stem. Porpoises here learn to navigate currents and hunt in running water. We even simulate ship noises to acclimate them," Zheng said.

In April 2023, two porpoises trained in this base were released into the Yangtze's main stream near Laowan. Three months of monitoring showed their successful integration into a wild group. At the same time, another two porpoises were released into the Shishou section of the Yangtze, after five months of rewilding training at Jiaozi River, a small branch of the Yangtze River, near the Tian'ezhou oxbow. Currently, three more porpoises are undergoing training in the Laowan oxbow, slated for release later this year.

"We hope the reintroduced porpoises can aid wild population recovery in the Yangtze," Zheng said.

China's success in finless porpoise ex-situ conservation has reversed international skepticism. This innovation stands as the world's first successful case of small cetacean ex-situ conservation, offering Chinese wisdom and a Chinese model for global conservation efforts.

In June 2025, 19 officials and cetacean experts from five Southeast Asian countries visited IHB to study the Yangtze experience, seeking solutions for the critically endangered Mekong Irrawaddy dolphin while exploring opportunities for international collaboration on cetacean conservation. ■