Integrating complementary methods to improve diet analysis in fishery-targeted species

Developing efficient, reliable, cost-effective ways to identify diet is required to understand trophic ecology in complex ecosystems and improve food web models. A combination of techniques, each varying in their ability to provide robust, spatially and temporally explicit information can be applied to clarify diet data for ecological research. This study applied an integrative analysis of a fishery-targeted species group - Plectropomus spp.in the central Great Barrier Reef, Australia by comparing three diet-identification approaches. Visual stomach content analysis provided poor identification with ~14% of stomachs sampled resulting in identification to family or lower. A molecular approach was successful with prey from ~80% of stomachs identified to genus or species, often with several unique prey in a stomach. Stable isotope mixing models utilising experimentally-derived assimilation data, identified similar prey as the molecular technique but at broader temporal scales, particularly when prior diet information was incorporated. Overall, Caesionidae and Pomacentridae were the most abundant prey families (>50% prey contribution) for all Plectropomus spp., highlighting the importance of planktivorous prey. Less abundant prey categories differed among species/colour phases indicating possible niche segregation. This study is one of the first to demonstrate the extent of taxonomic resolution provided by molecular techniques, and, like other studies, illustrates that temporal investigations of dietary patterns are more accessible in combination with stable isotopes. The consumption of mainly planktivorous prey within this species group has important implications within coral reef foodwebs and provides cautionary information regarding the effects that changing resources could have in reef ecosystems.

为解析复杂生态系统的营养生态学特征、优化食物网模型，亟需开发高效、可靠且成本效益优异的饮食识别技术。多种技术在提供稳健、时空分辨率明确的信息方面能力各有差异，通过组合应用这些技术可有效厘清生态研究中的饮食相关数据。本研究以澳大利亚中部大堡礁（Great Barrier Reef）的渔业目标物种群——石斑鱼属（Plectropomus spp.）为研究对象，通过对比三种饮食识别方法开展整合分析。视觉胃含物分析法的识别效果较差，约14%的采样胃仅能鉴定至科及更低分类阶元；分子鉴定法效果优异，约80%的采样胃内猎物可鉴定至属或种水平，且单个胃中常存在多种独特猎物。基于实验推导的同化数据构建的稳定同位素混合模型（stable isotope mixing models），能够鉴定出与分子技术一致的猎物类群，但可覆盖更宽泛的时间尺度，尤其是在整合已有饮食信息的情况下。总体而言，对于所有石斑鱼属物种而言，梅鲷科（Caesionidae）和雀鲷科（Pomacentridae）是最主要的猎物科（猎物贡献占比超50%），凸显了浮游生物食性猎物的重要性。丰度较低的猎物类群则因物种/体色变型而异，这暗示了潜在的生态位分化。本研究是首批阐明分子技术所能提供的分类学分辨率水平的研究之一，与其他同类研究一致，本研究证实结合稳定同位素技术可更便捷地开展饮食模式的时间尺度调查。该物种群主要捕食浮游生物食性猎物这一现象，对珊瑚礁食物网具有重要意义，同时也为探讨资源变化对礁区生态系统的影响提供了警示性参考。