Trophic overlap of lionfish (Pterois volitans) and two native predators (Lutjanus apodus and Cephalopholis cruentata) in the western Caribbean

Abstract Impact of invasive species on native biota may be due to predation, competition for space or food, or indirect effects. Lionfish (Pterois volitans), invasive in the western Atlantic, is a voracious generalist predator, so it is expected to have a significant trophic overlap with native fishes of comparable size and habits. The goal of this study was to determine the diets of potential competitors of the lionfish, in particular a grouper, Cephalopholis cruentata (Graysby), and a snapper, Lutjanus apodus (Schoolmaster), and to compare them to the diet of lionfish in Xcalak, southern Mexican Caribbean. Stomach contents were analyzed and electivity and diet overlap were estimated. The trophic overlap between the lionfish and the two putative competitors, especially the grouper, was high, including prey that was consumed by the predators in higher proportion than the relative abundance of the prey in the environment, and probably at the same time of day. Lionfish and grouper shared as important diet items Stegastes sp., Halichoeres sp., Brachyura, and Palaemonidae, and most full stomachs were found during the early morning. The hypothesis of competition between them for particular prey is supported, so we advise to continue the culling programs of lionfish and also to monitor the abundance of the possible native competitors.

摘要
入侵物种对本地生物群落的影响可归因于捕食、空间或食物竞争，亦或是间接效应。入侵西大西洋的蓑鲉（Pterois volitans）是一种贪婪的广食性捕食者，因此预计其与体型、习性相近的本地鱼类存在显著的营养生态位重叠。本研究旨在明确蓑鲉潜在竞争者的食性，具体为灰鮨（Cephalopholis cruentata，Graysby，一种石斑鱼）和校长笛鲷（Lutjanus apodus，Schoolmaster，一种笛鲷），并将其食性与墨西哥加勒比海南部卡尔阿克（Xcalak）海域的蓑鲉食性进行对比。研究通过分析胃含物，评估了捕食选择性与食性重叠程度。结果显示，蓑鲉与这两种疑似竞争者（尤其是灰鮨）之间的营养重叠度较高，二者捕食的猎物占比高于该猎物在环境中的相对丰度，且捕食活动时段大概率重合。蓑鲉与灰鮨的重要摄食对象包括雀鲷属（Stegastes sp.）、海猪鱼属（Halichoeres sp.）、短尾下目（Brachyura）和长臂虾科（Palaemonidae），且多数饱满的胃样本采集于清晨。二者针对特定猎物存在竞争的假说得到了支持，因此我们建议持续开展蓑鲉扑杀计划，并对潜在本地竞争者的种群丰度进行监测。