Fish as Indicators of Coral Reef Ecosystem Status

Monitoring coral reef health is essential for managing biodiversity and ecosystem

services in the face of accelerating environmental change. Here, we assess whether

aggregated reef fish indicators at the assemblage and family level can reflect variation

in coral reef benthic condition, structural complexity, and human pressure, across 77

sites in the western and central Indian Ocean. Our findings reveal that fish indicators

exhibit variable sensitivity and specificity to these ecological gradients. Human gravity

was the strongest and most consistent predictor across both assemblage-level and

family-level metrics, particularly for biomass and length-based indicators. Mean

assemblage trophic level, grouper (Epinephelidae) and butterflyfish (Chaetodontidae)

biomass, and surgeonfish (Acanthuridae) abundance were responsive to benthic

condition, while grouper length was the most specific indicator of reef structural

complexity. In contrast, parrotfish (Scarinae) indicators were not significantly

associated with benthic condition, challenging the assumption that they are tightly

linked to reef condition or degradation in this region. These results underscore the

need for careful selection of fish indicators of coral reef status and demonstrate how

family-level indicators can provide specificity in response to pressures that is not

captured within aggregate assemblage indicators. We recommend that additional

family-level fish indicators of coral reef ecosystem integrity and function be considered

within Red List of Ecosystems assessments, and that targeted family-level indicators,

such as butterflyfish and grouper biomass for benthic status, grouper length for

rugosity and surgeonfish abundance for benthic status, complement existing reef

benthic monitoring within global coral reef reporting frameworks such as the Global

Coral Reef Monitoring Network.

面对日益加速的环境变化，监测珊瑚礁健康状况对于生物多样性管理与生态系统服务维系至关重要。
本研究针对印度洋西部与中部的77个调查点位，评估以群落与科分类阶元汇总的礁鱼类指标能否反映珊瑚礁底栖状况、结构复杂度与人类活动压力的变化。
研究结果显示，礁鱼类指标对上述生态梯度的敏感性与特异性存在显著差异。
人类活动强度是群落与科分类阶元指标体系中最强且最稳定的预测因子，尤其在生物量与基于体长的指标中表现突出。
群落平均营养级、石斑鱼（Epinephelidae）与蝴蝶鱼（Chaetodontidae）的生物量，以及刺尾鱼（Acanthuridae）的丰度均与底栖状况显著相关；而石斑鱼体长则是反映珊瑚礁结构复杂度最具特异性的指标。
与之相反，鹦嘴鱼（Scarinae）相关指标与底栖状况无显著关联，这对该区域内“鹦嘴鱼与珊瑚礁状况或退化紧密相关”的既有假设提出了挑战。
本研究结果凸显了审慎选取珊瑚礁状态监测鱼类指标的必要性，并证实科分类阶元指标可捕捉到群落整体指标无法反映的压力响应特异性。
我们建议在《生态系统红色名录》评估中纳入更多用于监测珊瑚礁生态系统完整性与功能的科分类阶元鱼类指标；同时提出，可选取针对性的科阶元指标——如用于反映底栖状况的蝴蝶鱼与石斑鱼生物量、用于反映礁体粗糙度的石斑鱼体长，以及用于反映底栖状况的刺尾鱼丰度——来补充全球珊瑚礁报告框架（如全球珊瑚礁监测网络（Global Coral Reef Monitoring Network））中现有的礁体底栖监测工作。