Ecologists have identified significant ecological issues surrounding the release of hybrid groupers into Hong Kong’s coastal waters, a practice often linked to religious ‘mercy release’ ceremonies. Research indicates that the hybrid species known as the Tiger Grouper-Giant Grouper hybrid (TGGG), or Sabah grouper, disrupts local marine ecosystems by filling specific ecological roles and may evolve into a dominant predator. This pioneering study is the first to apply advanced DNA metabarcoding techniques to analyze the diet of this hybrid fish, emphasizing the urgent need for increased public awareness and conservation efforts to mitigate unintended ecological consequences.
A group of ecologists from the School of Biological Sciences (SBS) and the Swire Institute of Marine Science (SWIMS) at The University of Hong Kong (HKU) have uncovered significant ecological challenges linked to the introduction of hybrid groupers in Hong Kong’s coastal areas, often a result of the traditional ‘mercy release’ practices.
Their findings reveal how the Tiger Grouper-Giant Grouper hybrid (TGGG), also referred to as the Sabah grouper, interferes with local marine habitats by taking advantage of particular ecological roles and has the potential to rise as a primary predator. This research is noteworthy as the first to use innovative DNA metabarcoding methods to explore the dietary habits of this hybrid species, underscoring the pressing necessity for public education and conservation initiatives to diminish unintended ecological impacts. The study results have been published in the journal Reviews in Fish Biology and Fisheries.
Hybrid Groupers: A Favored Market Fish with Hidden Ecological Risks
The TGGG is formed through aquaculture by combining the Tiger Grouper (Epinephelus fuscoguttatus) and the Giant Grouper (Epinephelus lanceolatus). Its large size and rapid growth make it a popular choice in Hong Kong’s fish markets. Additionally, its cost-effectiveness and size have made it a preferred species for local mercy release customs, where animals are released as a form of spiritual merit. However, these seemingly altruistic acts can lead to substantial ecological consequences.
To understand the ecological effects of freeing hybrid groupers into local waters, our research team applied DNA metabarcoding to analyze the diet of the TGGG. They were the first to utilize this technique to assess the dietary habits of this hybrid species by extracting and sequencing DNA from the stomach contents of the fish, allowing them to identify prey even if it was completely digested or decomposed. This cutting-edge approach provides a detailed and accurate insight into the feeding behavior of the hybrid and its role in local marine ecosystems.
Advanced DNA Analysis Sheds Light on the Danger
The study found that TGGG is a formidable predator with a diverse diet, consuming various prey species that native fish typically do not eat, including fish, crustaceans, and cephalopods. By capitalizing on available ecological opportunities and gaps where resources or habitats are underused, the TGGG disrupts local food webs and is poised to thrive and become a major predator.
‘Our research shows that the TGGG is more than just another introduced species; it has the potential to greatly disturb food chains and alter coastal ecosystems,’ stated Professor Celia SCHUNTER from HKU SBS and SWIMS, the lead investigator of the study.
The researchers warn that the hybrid’s rapid growth, substantial size, and absence of natural predators in Hong Kong’s waters make it an exceptionally aggressive species. These traits, combined with available ecological niches, represent a real threat to marine biodiversity stability in Hong Kong’s coastal environments.
The study also sheds light on how mercy release practices contribute to the introduction of non-native species like the TGGG into local ecosystems. Dr. Arthur CHUNG, a postdoctoral fellow at HKU SBS and SWIMS and a co-author of the study, emphasized the need to recognize these dangers, saying, ‘This research underscores the importance of diligent monitoring and management to reduce the unintended effects of human behaviors on biodiversity.’
The researchers highlighted that raising public awareness and enforcing stricter conservation measures are crucial for mitigating the ecological damage caused by mercy releases and other human actions. Such initiatives are vital to preserving the well-being of Hong Kong’s marine environments.
