 |
| The Tiger Grouper-Giant Grouper hybrid (TGGG), also known as the Sabah grouper, has been introduced into Hong Kong waters through the religious practice of mercy release, impacting the balance of marine ecosystems. Credit: Arthur Chung. |
Ecologists from the University of Hong Kong's School of Biological Sciences (SBS) and the Swire Institute of Marine Science (SWIMS) have identified major ecological risks linked to the release of hybrid groupers into Hong Kong's coastal waters, a practice often associated with religious ‘mercy release’ rituals.
Their research reveals that the Tiger Grouper-Giant Grouper hybrid (TGGG), also known as the Sabah grouper, disrupts local marine ecosystems by occupying unique ecological niches and potentially becoming a dominant predator.
This study is the first to use advanced DNA metabarcoding to analyze the hybrid's diet, emphasizing the urgent need for public awareness and conservation efforts to prevent unintended ecological consequences.
The findings have been published in Reviews in Fish Biology and Fisheries.
Hybrid Groupers: A Popular Market Species with Hidden Ecological Risks
The Tiger Grouper-Giant Grouper hybrid (TGGG), bred through aquaculture by crossing the Tiger Grouper (Epinephelus fuscoguttatus) with the Giant Grouper (Epinephelus lanceolatus), is highly valued for its rapid growth and large size, making it a common presence in Hong Kong’s fish markets.
Its affordability and impressive appearance have also made it a popular choice for local mercy release rituals, where animals are set free into the wild for spiritual merit. However, this well-intentioned practice carries serious ecological risks.
To investigate the potential impacts of releasing hybrid groupers into Hong Kong’s coastal waters, researchers employed DNA metabarcoding to analyze the species' diet.
In a groundbreaking study, the research team became the first to apply this advanced technique to the TGGG, extracting and sequencing DNA from stomach contents to identify prey—even when fully digested or fragmented. This cutting-edge approach offers a precise and comprehensive understanding of the hybrid's feeding patterns and its influence on local marine ecosystems.
Innovative DNA analysis reveals the threat posed by the TGGG
The study identifies the TGGG as a formidable predator with a unique diet, preying on species not typically consumed by native creatures, such as fish, crustaceans, and cephalopods. By exploiting ecological gaps and underused resources, the TGGG disrupts local food webs, positioning itself as a dominant predator likely to thrive and establish dominance.
"Our findings show that the TGGG is more than just another invasive species; it has the potential to significantly alter trophic dynamics and reshape coastal ecosystems," said Professor Celia Schunter from HKU SBS and SWIMS, the study's lead investigator.
The researchers warn that the TGGG’s rapid growth, large size, and lack of natural predators in Hong Kong’s waters make it highly competitive. Combined with vacant ecological niches, these factors pose a serious threat to marine biodiversity.
The study also highlights the role of mercy release practices in introducing non-native species like the TGGG into local waters. Dr. Arthur Chung, postdoctoral fellow at HKU SBS and SWIMS and co-author of the study, stressed the need for caution: "This study emphasizes the importance of monitoring and managing human activities to prevent unintended consequences for biodiversity."
The researchers urge increased public education and stricter conservation measures to mitigate the ecological damage caused by mercy release and other human activities, which are crucial to preserving the health of Hong Kong’s marine ecosystems.
The study, authored by Arthur Chung et al., titled "Distinct resource utilization by introduced man-made grouper hybrid: an overlooked anthropogenic impact from a longstanding religious practice", was published in Reviews in Fish Biology and Fisheries (2024). It explores the ecological impact of the TGGG, an introduced man-made grouper hybrid, and highlights how its unique feeding habits disrupt local ecosystems. The paper provides a comprehensive analysis of how religious practices, particularly mercy releases, contribute to the spread of non-native species and their potential to alter marine food webs.
For full details, you can access the study here: DOI: 10.1007/s11160-024-09907-6.