Do macrophytes act as restaurants for fishes in a tropical beach? An approach using stomach content and prey availability analyses

Abstract Tropical sandy beaches have low primary productivity, thus depend on external food sources. Generally, allochthonous macrophytes, form the basis of these food webs, also may influence factors such as fish’s abundance, richness, species composition, and biomass. However, the role of such drifting macrophytes to the feeding ecology of fishes in tropical sandy beaches is uncertain. We aim to explain if this microhabitat acts as restaurants for fishes in a tropical sandy beach by performing stomach content and prey availability analyses using Stellifer punctatissimus as a model because it has an association with drifting macrophytes mainly on sandy beaches along the northeastern Brazilian coast. The most consumed prey was amphipods, which were eaten in a specialist way, especially by the smaller fishes. The prey availability along with electivity index suggested that this species may choose amphipods. Seasonal variations suggest that the fishes did not locate suitable prey as an effect of the availability, this can be also explained by optimal foraging theory and compensatory growth. Here, we redefined the S. punctatissimus trophic guild as zooplanktivorous, highlighting drifting macrophytes as restaurants for fishes in a tropical sandy beach as they are the main source of food.