First community level description of rocky reefs at the Cabo Blanco absolute natural reserve on Costa Rica’s Pacific Coast

The Cabo Blanco Absolute Natural Reserve (RNACB) is located at the southern end of the Nicoya Peninsula in Costa Rica. This research aimed to provide the first community-level description of rocky reefs within RNACB. Data was collected in June 2018, covering a total area of 1680 m² monitored across six transects at two depths: -5 m and -20 m. A total of 44 macroinvertebrate species were recorded, primarily represented by suspension feeders and filter feeders, mainly including ascidians and octocorals, as well as 48 fish species, notably dominated by macroinvertivore species such as surgeonfish and parrotfish. The biomass recorded was 4.91 tons.ha-1, with the highest values predominantly observed at deeper sites. Sessile macroinvertebrates were predominantly found in deeper areas, while mobile organisms showed no specific depth preference. The average biomass of fish was greater in the deeper zones, and in general, RNACB biomass exceeded the expected values for the Costa Rican Pacific.