Feeding Ecology of the Large-Scale Triggerfish, Canthidermis macrolepis (Boulenger, 1888), from Yemeni Coastal Waters

Information on fish feeding ecology is crucial for understanding trophic interactions, energy flow, and ecosystem dynamics in marine environments. Although the feeding ecology of several balistid species has been well documented, the trophic dynamics of the large-scale triggerfish, Canthidermis macrolepis, remain largely unstudied. To address this gap and define its ecological role, we investigated the diet and feeding intensity of C. macrolepis harvested from the Yemeni Red Sea coast between June and October 2025. Stomach content analysis (N = 57) was performed utilizing qualitative taxonomic identification and quantitative metrics, specifically frequency of occurrence (%F) and volumetric percentage composition (%C). The results characterize C. macrolepis as an active pelagic carnivore. The diet was predominantly composed of small teleosts, with zooplanktonic crustaceans serving as a critical secondary resource. Benthic invertebrates (sipunculids and worms), small mollusks, and macroalgae were present only as minor, opportunistic dietary components. Furthermore, feeding intensity was exceptionally high (Fullness Index: 98.25%; Vacuity Index: 1.75%), indicating continuous foraging activity. These findings establish C. macrolepis as a pelagic predator, differentiating its ecological niche from that of heavily benthic-dependent reef triggerfishes, and provide essential baseline trophic data to support regional ecosystem-based fisheries management.