Original title: First report of Centrocestus formosanus infection associated with mass mortality in the critically endangered Chinese Bahaba (Bahaba taipingensis)
Zhen Wu, Liwen Xu, Lin Yan, ChiHai Ji +5 · September 2026
The Chinese bahaba is a critically endangered fish that can live in both the sea and brackish river mouths. Between November 2025 and January 2026, a deadly disease outbreak struck these fish at an aquaculture facility in China. Researchers investigated the dead fish to uncover what killed them. They discovered that a freshwater parasitic flatworm called Centrocestus formosanus had spilled over into the fish. Swimming parasite larvae thrive in low-salinity water, precisely matching the brackish conditions where the fish were kept. The parasites burrowed into the gills and formed cysts. This triggered a severe immune reaction in the fish. The gills filled with excess mucus, swelled, scarred, and fused together, destroying the delicate breathing tissue. The researchers found an average of 3832 ± 473 parasites per fish, showing that this parasite poses an acute, newly recognized threat to saving this endangered species.
Imagine you have a pet fish that lives in saltwater. You decide to slowly lower the salt level because it can handle both salt and fresh water. But at that exact low-salt level, tiny invisible organisms that normally only live in freshwater suddenly become active and start attacking your fish's gills. Here, the fish is the Chinese bahaba, kept at low salinity for convenience, but that low salt level is exactly what the parasite Centrocestus formosanus needs to swim and infect, turning a safe environment into a death trap.
This discovery means that captive breeding programs for Chinese bahaba must now control for a parasite they never expected in saltwater. Because the parasite thrives at the low salinity that the fish tolerate, any brackish-water holding facility becomes a lethal trap. Without new screening and water management, recovery efforts for this critically endangered species could fail.
The abstract describes a single outbreak at one aquaculture base, so it does not establish whether wild Chinese bahaba in higher-salinity waters face the same risk. Only 10 infected fish were examined for histopathology. The study does not identify the intermediate snail host or the source of the parasite in the facility, so the route of introduction remains unknown.
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First report of Centrocestus formosanus infection associated with mass mortality in the critically endangered Chinese Bahaba (Bahaba taipingensis) — Zhen Wu, Liwen Xu, Lin Yan et al. — International journal for parasitology. Parasites and wildlife — doi:10.1016/j.ijppaw.2026.101280
Abstract licence: CC BY
Explanation generated by Synthesis from the abstract — it is not the original paper.