New DNA tracking helps spot rare ‘Tai O fish’ in HK waters after over a decade

By the Editorial Team · Tuesday, July 28, 2026

Researchers have detected the critically endangered Chinese bahaba in Hong Kong waters for the first time in over ten years using a new environmental DNA (eDNA) method developed by scientists from Lingnan University and South China Normal University. This finding indicates potential migration of hatchery-released juveniles into the area and provides a non-invasive tool to support ongoing conservation and monitoring efforts for the species.

Researchers have successfully detected the presence of the critically endangered Chinese bahaba, also known as the “Tai O fish,” in Hong Kong waters for the first time in over a decade using newly developed environmental DNA (eDNA) technology. The detection marks a significant breakthrough in monitoring the species, which has been driven to near extinction by overfishing.

The study was co-led by Jack Ip Chi-ho, an assistant professor in the division of science at Lingnan University, and Wang Junjie, a professor at South China Normal University. Their team developed a highly sensitive genetic identification method capable of detecting minute traces of the Chinese bahaba’s DNA left in the marine environment, allowing researchers to confirm the fish’s presence without physical capture.

The breakthrough follows the release of 40 hatchery-reared juvenile Chinese bahaba into the Pearl River Estuary in August 2025. The new detection occurred in September 2025, suggesting that some of these released fish may have migrated into Hong Kong’s western waters.

“The new detection technology developed by our research team is highly sensitive,” Ip said, noting that even a tiny amount of eDNA left behind by the fish—through mucus, faeces, or other biological materials—can be accurately identified. Environmental DNA refers to genetic material organisms shed into their surroundings, which can be sampled through seawater collection.

The Chinese bahaba is the largest croaker species in the South China Sea, capable of reaching lengths up to two meters. Historically abundant near Tai O, a fishing village on Lantau Island, the species has nearly vanished due to intense fishing pressure targeting its swim bladder, prized in traditional medicine.

Conventional survey methods like trawling have proven ineffective in monitoring the species because of its rarity and elusive behavior. Ip highlighted that relying on eDNA analysis avoids disturbing the seabed and reduces harm to other marine life, as it requires only seawater samples rather than catching fish.

Between January and September 2025, the research team collected 414 seawater samples from 23 sites across Hong Kong’s western waters. Positive eDNA detection occurred at four locations in September: Tai O, Sha Chau and Lung Kwu Chau Marine Park, Southwest Lantau Marine Park, and Sunny Bay. Tai O showed the highest frequency and concentration of Chinese bahaba DNA.

The application of this innovative eDNA method represents a valuable tool for conservation efforts aimed at understanding the distribution and potential recovery of this critically endangered species in the region.

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