Resource use of three juvenile scarids (Cryptotomus roseus, Scarus iseri, Sparisoma radians) in Caribbean seagrass beds

The bucktooth parrotfish Sparisoma radians, the striped parrotfish Scarus iseri and the bluelip parrotfish Cryptotomus roseus are three herbivorous fishes commonly found at juvenile stages in Caribbean seagrass beds. While the diet of the three species as adults is relatively well known, few studies have been conducted on the feeding patterns of juveniles. In this study, the resource use of the juveniles of three scarid species were studied using two complementary methods: gut content and stable isotope analyses (13C:12C and 15N:14N ratios). Bayesian mixing model approaches were used to calculate the contribution of each food item to fish diets (SIAR, mixing models). The three parrotfish species appeared to rely essentially on the consumption of fleshy macrophytes. Cryptotomus roseus consumed more benthic invertebrates and presented a higher trophic level than the two other scarid species. Scarus iseri presented a higher assimilation of benthic biofilm, in accordance with the high percentage of sediment in its gut content, and Sparisoma radians assimilated more Thalassia testudinum leaves. This research highlighted a food resources partitioning among the juveniles of the three herbivorous fishes, probably to avoid inter-specific competitive interactions for the most palatable food at a critical stage of their life.

Keywords: Gut content analyses; Trophic niche; Stable isotopes analyses