China closed its longest river to commercial fishing in January 2021. Five years on, the fish are getting bigger - and that, more than any headline biomass figure, is what has fisheries scientists paying attention.
A 2026 study published in Acta Hydrobiologica Sinica examined long-term fish-monitoring data from the Yangtze's main stem before and after the ban took effect. Eight species showed a statistically significant increase in body size. Ten showed a higher proportion of sexually mature individuals.
Body length is not a vanity metric in fisheries science. Larger fish produce far more offspring, and a population with more mature adults in it has a healthier age structure - the difference between a genuine recovery and a temporary flush of juveniles that will never make it to spawning size. Many Yangtze species are slow-growing and need several years to reach maturity, which is precisely why the signal took half a decade to appear.
The broader picture had already turned. A study published in Science in February, comparing the two years before the ban with the two years after, found fish biomass had more than doubled and diversity had improved by 13 per cent. The Economist has since reported the total weight of fish in the river tripling over recent years. Separate monitoring reported in The Innovation Water documented 134 endemic fish species between 2021 and 2025, 25 more than pre-ban surveys found.
"It is really fantastic news. It is one of the first times that we can say that government measures have not just worked, but have really improved things," said Sebastien Brosse of the University of Toulouse, part of the team behind the Science paper. He called it the most positive freshwater conservation story he had seen anywhere in the world in 20 years.
Fangyuan Xiong of the Chinese Academy of Sciences, who led that study, framed it as a template rather than a curiosity. "The results reported in this study [...] provide hope that in an era of global biodiversity decline, ambitious political decisions that support large-scale restoration efforts can help reverse the ecosystem damages of the past and lead to a brighter future," Xiong said.
The scale of the intervention is worth stating plainly. The 6,300-kilometre river serves a population of around 400 million and a large share of the world's manufacturing. Fish stocks had fallen by roughly 85 per cent. Piecemeal restrictions had failed for decades before the central government imposed the full 10-year moratorium across the main stem and major tributaries. Around $3 billion went on compensating and re-employing some 200,000 fishers, with many of the 100,000 boats involved scrapped outright. The design drew on evolutionary game theory to model how communities, local governments and the central government would each respond to different mixes of punishment and reward - an unusually deliberate piece of policy engineering for a fishing closure.
The emblematic casualty is still the baiji, the near-blind freshwater dolphin wiped out earlier this century by pollution, dams, ship traffic and fishing with electricity and dynamite. Its surviving relative has fared better: observed numbers of the Yangtze finless porpoise rose from about 400 to 600, according to Brosse.
Nobody involved is calling it won. The authors of the Acta Hydrobiologica Sinica work stress that five years is half a programme, and that continued monitoring is essential before drawing long-term conclusions. Chen Yushun of the Chinese Academy of Sciences' Institute of Hydrobiology, a co-author on the Science study, has described the recovery as early-stage rather than secured.
The listed threats are specific. Illegal fishing persists, particularly in the Gan tributary, and needs harder policing by local authorities. Water quality remains a problem. The critically endangered Chinese sturgeon still cannot reach its spawning grounds past the giant hydropower plants on the river. A 2022 review in The Innovation made the point bluntly: a fishing ban alone will not restore the ecosystem unless habitat connectivity, water quality and river management improve alongside it.
Brosse has urged authorities on other major waterways - almost all of them deteriorating - to study what China did here, singling out the Mekong as a river facing much the same set of problems.
For anglers and fisheries managers elsewhere, the Yangtze is now the largest field trial in existence of a simple, unpopular proposition: stop taking fish out for long enough, pay the people whose livelihoods you end, and the river will do the rest. Five years in, the evidence says it partly works.
