南海美济礁礁栖鱼类群落结构和功能群特征长期变动趋势及其影响因素

Coral reefs are the most distinctive ecosystem in the South China Sea. The declines of coral reefs and their fish communities has attracted worldwide attention in recent decades. Fish are the crucial component of the new approaches to diagnose and recover the degraded coral reefs. Chinese scholars have accumulated rich experience in the resource structure, biology and population assessment of reef fish in the South China Sea, but few have studied the long-term changes of community structures and functional groups of reef fish and its mechanism. Based on the biological and hydro-acoustic data accumulated from 1997 to 2018 and 2011 to 2018, this project analyzed the inter-annual variation of dominant species, diversity, community structure and trophic structure of reef fish in the lagoon of the Meiji Reef in the South China Sea. The acoustic target strength spectrum and spectrum index of fish were established and used to study the effect of fishing intensity on the size structure of fish community. This project will elucidate the succession process of community structure of fish in the lagoon of the Meiji Reef and reveal the key factors that influence the succession process using the Hierarchical Mixed Effects Models by combined with temperature, PH, chlorophyll and fishing information, etc. The results of the project will enhance our understanding of the key scientific issues such as the succession process of community structure of reef fish and its responses to environmental changes and human activities in the South China Sea.

珊瑚礁是我国南海最具特色的生态系统。近几十年来，珊瑚礁及其鱼类群落衰退问题引起了全球的广泛关注。鱼类是诊断和修复退化珊瑚礁新方法的关键组分。我国学者在南海珊瑚礁鱼类资源结构、生物学、种群评估等方面积累了丰富经验，而对珊瑚礁鱼类群落结构和功能群的长期变动过程和机制的研究甚少。本项目以南海美济礁之礁栖鱼类为研究对象，以1997–2018年及2011–2018年积累的生物学和水声学数据为基础，分析多样性、群落结构、食性功能群等的年际变动；引入鱼类声学目标强度谱和谱指数，研究捕捞强度对鱼类群落大小结构的影响；阐明美济礁鱼类群落结构的演替过程；结合温度、PH、叶绿素等生境数据和捕捞信息，利用分层混合效应模型，揭示影响其演替的主要因素。研究结果将提升对南海珊瑚礁鱼类群落结构演替过程及其对环境变化和人类活动的响应等关键科学问题的认识。

珊瑚礁鱼类作为珊瑚礁生态系统的重要组分，其研究、养护及可持续发展受到全球广泛关注。该项目研究南海美济礁鱼类种类组成、多样性和食性功能群变动；典型珊瑚礁鱼类生物学特征变动；构建美济礁鱼类声学粒径谱，分析其粒径结构特征。主要结果如下：1.首次初步阐明了南海美济礁珊瑚礁鱼类结构和食性功能群特征的长期变动规律，美济礁部分鱼类消失或明显减少，多样性和生产力明显下降，功能群结构组成趋于简单。分析认为，捕捞是造成鱼类多样性下降的主要因素，其次是珊瑚覆盖率下降。2.揭示了典型珊瑚礁鱼类种群特征的长期演变及其对外在胁迫的差异性响应，四带笛鲷(Lutjanus kasmira)、金带齿颌鲷(Gnathodentex aurolineatus)、尾纹九棘鲈(Cephalopholis urodeta)等鱼类的生存状况恶化。四带笛鲷衰退最明显，其次是金带齿颌鲷，尾纹九棘鲈无衰退趋势。3.鱼类声学粒径谱为研究珊瑚礁鱼类粒径结构提供了新的方法。相比手钓鱼类粒径谱，鱼类声学粒径谱在粒径级范围、粒径级连续性和均匀性、相应粒径级上鱼类丰度等均表现更好。美济礁瀉湖区极小型鱼类丰度占绝对优势，大型鱼类的比例极低。4.首次应用基于长度的贝叶斯生物量估计方法分析了南海珊瑚礁鱼类资源的开发状态，为南海珊瑚礁鱼类可捕规格制定提供了依据。评估的10种鱼类中，60%的种类遭受过度捕捞，20%已充分开发。