This data set consist of three parts: (1) fish underwater visual census data (total length > 3 cm) from 20 reef sites in North Malé Atoll, the Maldives; (2) combined biomass composition data for each fish species at each body mass class; and (3) stable isotope data (δ15N, δ13C) from fish species contributing to 80% of biomass per size class (and some species collected to refer to others which were unavailable to be collected.