Released through the religious practice of mercy release, the Tiger Grouper-Giant Grouper hybrid (TGGG), also known as the Sabah grouper, now swims in Hong Kong waters, affecting the balance of marine ecosystems. Photo credit: Arthur Chung.
被放生的老虎斑龍躉混種魚（又稱沙巴龍躉）已在香港水域迅速繁殖，對本地海洋生態系統的平衡造成嚴重干擾。圖片提供：鍾炘熾
Ecologists from the School of Biological Sciences (SBS) and the Swire Institute of Marine Science (SWIMS) at The University of Hong Kong (HKU) have identified significant ecological risks associated with the release of hybrid groupers into Hong Kong’s coastal waters, a practice often linked to religious ‘mercy release’ rituals.
Their study highlights how the Tiger Grouper-Giant Grouper hybrid (TGGG), also known as the Sabah grouper, disrupts local marine ecosystems by exploiting unique ecological niches and potentially becoming a dominant predator. This research, the first to use advanced DNA metabarcoding to analyse the diet of this hybrid species, underscores the urgent need for public education and conservation measures to mitigate unintended ecological impacts. The findings have been published in the journal Reviews in Fish Biology and Fisheries.
Hybrid Groupers: A Popular Market Species with Hidden Ecological Threats
The TGGG is a hybrid species bred through aquaculture by crossing the Tiger Grouper (Epinephelus fuscoguttatus) with the Giant Grouper (Epinephelus lanceolatus). Valued for its large size and rapid growth, it is a common sight in Hong Kong’s fish markets. Its affordability and impressive size have also made it a popular choice for local mercy release practices, where animals are released into the wild as an act of spiritual merit. However, this seemingly benevolent act has significant ecological consequences.
To explore the potential ecological effects of releasing hybrid groupers into Hong Kong’s coastal waters, our research team utilised DNA metabarcoding to analyse the diet of TGGG. Becoming the first to apply this method to study the dietary habits of this hybrid species, the team extracted and sequenced DNA from the hybrid’s stomach contents, allowing them to identify its prey, even when the prey was fully digested or fragmented. This innovative approach provides a detailed and accurate picture of the hybrid’s dietary habits and its interactions with local marine ecosystems.
Innovative DNA Analysis Highlights the Threat
The study found that the TGGG is a formidable predator with a distinctive diet, feeding on various prey species not typically consumed by native species—including fish, crustaceans, and cephalopods. By exploiting broader ecological niches and gaps in the ecosystem where resources or habitats are underused, the TGGG disrupts local food webs and is highly likely to thrive and establish itself as a dominant predator.
‘Our findings show that the TGGG is not just another introduced species, it has the potential to significantly disrupt trophic dynamics and reshape coastal ecosystems,’ said Professor Celia SCHUNTER of HKU SBS and SWIMS, the study’s lead investigator.
The researchers warn that the rapid growth, large size, and absence of natural predators in Hong Kong’s waters make it an exceptionally competitive species. These traits, combined with the availability of vacant ecological niches, pose a serious threat to the balance of marine biodiversity in Hong Kong’s coastal ecosystems.
The study also draws attention to the role of mercy release practices in introducing non-native species like the TGGG into local waters. Dr Arthur CHUNG, the postdoctoral fellow of HKU SBS and SWIMS and co-author of the study, emphasised the importance of addressing these risks, ‘This study underscores the need for careful monitoring and management to mitigate the unintended impacts of human activities on biodiversity.’
The researchers stressed that public education and stricter conservation measures are essential to minimising the ecological damage caused by mercy release and other human activities. These efforts are critical for preserving the health of Hong Kong’s marine ecosystems.
About the journal paper: Chung, A., & Schunter, C. (2024). Distinct resource utilization by introduced man-made grouper hybrid: an overlooked anthropogenic impact from a longstanding religious practice. Reviews in Fish Biology and Fisheries. https://doi.org/10.1007/s11160-024-09907-6
News links: 1, 2, 3, 4, 5, 6, 7
香港大學（港大）生物科學學院和太古海洋科學研究所的生態學家發現，傳統宗教儀式「放生」中將混種石斑魚釋放到香港沿岸水域的行為，可能帶來嚴重的生態風險。研究發現，經常用於放生的老虎斑龍躉混種魚（Tiger Grouper-Giant Grouper，TGGG），俗稱沙巴龍躉，具有獨特的生態棲位（ecological niche），流入本地海域後可成為強勢的捕食者，嚴重干擾本地海洋的生態系統。該研究首次運用先進的 DNA 元條形碼技術分析沙巴龍躉的食性，強調須加強公眾教育和採用保育措施，以減少不必要的生態破壞。研究結果已發表於《魚類生物學與漁業評論(Reviews in Fish Biology and Fisheries)》期刊。
放生行為的隱藏禍害
沙 巴 龍 躉 是 一 種 通 過 水 產 養 殖 、 由 老 虎 斑 （Epinephelus fuscoguttatus） 與 龍 膽 石 斑（Epinephelus lanceolatus）雜交而成的混種魚，因其體型具大、成長迅速而深受市場青睞，因而成為香港魚市場中的常見物種。由於價格相對便宜且體型顯眼，沙巴龍躉成為「放生」活動中的熱門選擇。然而，這種本屬善意的行為卻對生態環境造成重大的影響。為了探討沙巴龍躉被放生到沿岸水域後可能帶來的生態影響，研究團隊首次運用 DNA 元條形碼技術，通過分析其消化系統中食物殘留的 DNA 來研究其食性。該技術的特點是即使獵物已被消化或分解，仍能準確辨識出其物種。這種創新的方法精確揭示了沙巴龍躉的飲食習慣及其對本地海洋生態系統的影響，為理解其生態互動提供了重要而深入的見解。
創新 DNA 分析揭示威脅
研究發現，沙巴龍躉是一種極具競爭力的外來捕食者，憑藉其獨特的飲食習性和高度適應能力，對本地生態系統構成嚴重威脅。牠們主要捕食本地魚類不常選擇的魚類、甲殼類及頭足類等，並能有效利用生態系統中未被其他物種佔據的資源及生態棲位，從而干擾食物鏈並破壞生態平衡。
研究同時指出，放生活動在將外來物種引入至本地水域方面扮演了關鍵角色。研究團隊警告，沙巴龍躉在香港水域內快速擴散，加上其體型龐大且缺乏天敵，將進一步威脅原有物種的存續，對香港沿岸生態系統的海洋生物多樣性帶來挑戰。港大生物科學學院與太古海洋科學研究所的 Celica SCHUNTER 教授表示：「研究結果表明，沙巴龍躉
並非普通的外來物種，它極有可能擾亂食物鏈，進而破壞沿岸生態系統的平衡。」該研究的共同作者、港大生物科學學院與太古海洋科學研究所的博士後研究員鍾炘熾博士強調，必須正視放生行為的潛在風險：「本研究突顯了加強監測與管理的必要性，以減輕人類活動對生物多樣
性帶來無意的影響。」
研究人員強調，推動公眾教育和加強保育措施，對於減少宗教活動及其他人類行為對生態造成的破壞至關重要。這些措施對於維護香港海洋生態系統的健康具有重要意義。
有關此研究的詳細內容，可參考以下論文：Chung, A., & Schunter, C. (2024). Distinct resource utilization by introduced man-made grouper hybrid: an overlooked anthropogenic impact from a longstanding religious practice. Reviews in Fish Biology and Fisheries.
相關研究論文可於以下網址查閱：https://doi.org/10.1007/s11160-024-09907-6