Ichthyofauna associated with a no longer standing decommissioned oil plataform in the Tropical Eastern Pacific (4°S, Peru)

Abstract Seabed resources contribute to one-third of global oil extraction, leading to the development of offshore oil platforms that act as artificial ecosystems supporting diverse fish and invertebrate assemblages. However, ecological studies on ichthyofauna associated with oil and gas structures along the Peruvian continental shelf remain limited. This study used underwater video footage collected across a depth gradient (0–40 m) divided into five strata around the MX-1 oil platform, located off Los Órganos (4°S, Piura, Peru), during austral spring (October 2022), using open-circuit SCUBA. Temperature and salinity were recorded with a hand-held CTD. Over six dives, a total of 7,969 individual fish were recorded, comprising 27 species from 13 families, including eight species targeted by fisheries. Fish belonged to two biogeographic provinces: Peruvian (n = 3) and Panamic (n = 20), with four species from the transition zone. Vertical distribution pattern was observed: species richness was highest in the shallowest stratum (0–5 m; n = 19), while fish abundance peaked in deeper layers (30–40 m). Carnivorous and planktivorous fish predominated. MX-1 functioned as a fish-aggregating device (FAD) and a local hotspot of fish diversity. Its partial removal could result in habitat loss, affecting associated assemblages, artisanal fisheries, and recreational activities.