Traces of genetic material collected from seawater have revealed the presence of the Chinese bahaba (Bahaba taipingensis) in the waters of western Hong Kong, the first scientific confirmation of the rare fish in the city for more than ten years.was nicknamed “sea panda“ Due to their low numbers, the giant marine fish had disappeared 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 assay for eDNA monitoring of the 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 bobtail living in Hong Kong for a decade without records
tracking fish without catching them
The Chinese bobcat lives only off the Chinese coast and is the largest member of the croaker fish family in the South China Sea, growing up to two meters long. Historically common around Tai O, where local villagers called it “Tai O fish”, the wild population declined rapidly due to high demand for its swim bladder, which is used in traditional medicine. This fish is now listed as a top-level protected wild animal in China.Standard fish surveys rely on dragging large nets, which can harm rare marine life and damage the seabed. To avoid this, the research team studied the fish’s genes to create an accurate testing method called qPCR.This new technology detects microscopic pieces of genetic material, such as skin mucus or waste left in the water, without mixing the shark with other types of fish.“There have been no recorded incidents of Chinese Bahaba in Hong Kong SAR waters for more than a decade,” the Ip said.“Given the extreme rarity of the species, the likelihood of encountering it through traditional survey methods is exceptionally low, making it difficult to understand its distribution. Reliable advanced monitoring techniques are essential to effectively track wild populations and evaluate the survival and adaptation of released juveniles into their natural habitats.”The IP pointed out the obvious advantages of testing the waters rather than capturing live animals.“The greatest advantage of eDNA technology lies in its non-invasive nature. It enables scientists to confirm the presence of a species without capturing or disturbing individual fish. Researchers 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. In addition to long-term monitoring of Chinese eel in the Pearl River Estuary and surrounding waters, the technology can also be integrated with other eDNA approaches to support biodiversity monitoring and provide valuable reference data for conservation planning in the Guangdong-Hong Kong-Macao Greater Bay Area.“
Water samples in local creeks
Between January and September 2025, researchers collected water from 23 locations in western Hong Kong. The team collected samples from key nature areas including Mai Po Nature Reserve, Sha Chau and Lung Kwu Chau Marine Parks, The Brothers Marine Park and Southwest Lantau Marine Park.Field teams took three one-litre water samples at each site during each visit, collecting a total of 414 seawater samples. To ensure that no foreign DNA was mixed into the laboratory tests, clean, distilled water was tested with the ocean samples.Lab tests found Chinese eel eDNA in water collected at four different locations in September 2025:
- tai o
- Sha Chau and Lung Kwa Chau Marine Park
- Southwest Lantau Marine Park
- Sunny Bay, near The Brothers Marine Park
Tai O showed the highest amount and most frequently detected traces of fish DNA among all positive sites.
Clues from recently released fish
The high DNA levels detected in Tai O in September 2025 match a local release event. A month earlier, in August 2025, wildlife groups released about 1,300 young, farm-raised Chinese eel into the nearby Pearl River estuary to boost wild numbers.Strong eDNA signals near Tai O suggest that many of these young fish swam into the waters of western Hong Kong after being freed.By proving that young fish migrated into local creeks, the water testing method gives scientists a safe way to track released fish and protect vital water areas throughout the region.