Traces of genetic material collected from seawater have revealed the presence of the Chinese bahaba (Bahaba taipingensis) in western Hong Kong waters, marking the first scientific confirmation of the rare fish in the city for over ten years.Nicknamed the “Panda of the Sea“ due to its low numbers, the giant sea fish had vanished from local records after years of heavy fishing.The research paper, published on the preprint server bioRxiv under the title Tracing the ‘Panda of the Sea’: Species-Specific qPCR Assays for eDNA Monitoring of Critically Endangered Bahaba taipingensis in the Pearl River Estuary, details how scientists from Lingnan University and South China Normal University tracked the fish using environmental DNA (eDNA) technology.
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The joint study was co-led by Jack Ip Chi-ho, assistant professor in the Division of Science at Lingnan University, and Junjie Wang of South China Normal University.
Trace DNA reveals critically endangered Chinese bahaba in Hong Kong after decade without records
Tracking fish without catching them
The Chinese bahaba lives only along the Chinese coast and is the biggest member of the croaker fish family in the South China Sea, growing up to two metres long. Historically common around Tai O, where local villagers called it the “Tai O fish,” wild populations dropped fast due to high demand for its swim bladder, which is used in traditional medicine. The fish is now listed as a top-level protected wild animal in China.Standard fish surveys rely on dragging large nets, which can hurt rare marine life and damage the seabed. To avoid this, the research team studied the fish’s genes to build a precise testing method called qPCR.This new technique spots microscopic bits of genetic material, like skin mucus or waste left in the water, without mixing up the bahaba with other fish types.“There has been no recorded occurrence of the Chinese bahaba in Hong Kong SAR waters for more than a decade,” said Ip.“Given the species’ extreme rarity, the chance of encountering it through conventional survey methods is exceptionally low, making it difficult to understand its distribution. Reliable advanced monitoring technology is essential for effectively tracking wild populations and evaluating the survival and adaptation of released juveniles in their natural habitats.”Ip pointed out the clear advantages of testing water instead of catching live animals.“The greatest advantage of eDNA technology lies in its noninvasive nature. It enables scientists to confirm the presence of a species without capturing or disturbing individual fish. Researchers simply need to collect seawater samples to conduct large-scale marine surveys within a short period of time, significantly reducing sampling efforts.”“The technology also provides conservation organizations with an effective tool to evaluate the outcomes of juvenile fish release programs. Beyond long-term monitoring of the Chinese bahaba in the Pearl River Estuary and nearby waters, the technology can also be integrated with other eDNA approaches to support biodiversity monitoring and provide valuable reference data for conservation planning across the Guangdong-Hong Kong-Macao Greater Bay Area.“
Water samples across local bays
Between January and September 2025, researchers collected water across 23 spots in western Hong Kong. The team gathered samples from key nature zones, including the Mai Po Nature Reserve, Sha Chau and Lung Kwu Chau Marine Park, The Brothers Marine Park, and Southwest Lantau Marine Park.Field teams took three one-litre water samples at each site during every trip, gathering 414 seawater samples in total. Clean, distilled water was tested alongside the ocean samples to ensure no outside DNA mixed into the lab tests.Lab tests found Chinese bahaba eDNA in water collected in September 2025 at four distinct spots:
- Tai O
- Sha Chau and Lung Kwu Chau Marine Park
- Southwest Lantau Marine Park
- Sunny Bay, near The Brothers Marine Park
Tai O showed both the highest amount and most frequent traces of fish DNA among all positive sites.
Clues from recent fish releases
The high DNA levels found at Tai O in September 2025 matched up with a local release program. One month earlier, in August 2025, wildlife groups released roughly 1,300 young, farm-raised Chinese bahaba into the nearby Pearl River Estuary to boost wild numbers.The strong eDNA signals near Tai O suggest that several of these young fish swam into western Hong Kong waters after being set free.By proving that young fish moved into local bays, the water testing method gives scientists a safe way to track released fish and protect important water zones across the region.
