Unusual reef fish biomass and functional richness at Malpelo, a remote island in the Tropical Eastern Pacific

Fish assemblages can vary across temporal and spatial scales due to changes in habitat structure and the influence of local factors such as wave exposure, depth and anthropogenic influence. This study presents a description of species richness, functional richness, density and biomass of fish assemblages of Malpelo Island, a Marine Protected Area located in the Tropical Eastern Pacific (TEP) region and considered a World Heritage site. Underwater visual censuses (n = 103) from two years and a local checklist were used to characterize the reef fish assemblage of Malpelo Island. Our results show a numerical dominance, during both sampling years, by the planktivore species Chromis atrilobata and Apogon atradorsatus, which are regional TEP endemic species. Among the most striking results found were the high biomass values (706.2 g/m2 ± 73.2 in 2010 and 879 g/m2 ± 116.2 in 2015) of large-bodied TEP endemic piscivorous species and the high functional diversity represented mainly by vulnerable species. The dominance in density and biomass of regional endemic species exemplifies the high endemism level within the TEP. High levels of fish biomass and functional richness suggest that Malpelo is one of the most pristine and vulnerable sites within the TEP region. Thus, Malpelo island represents a baseline for untouched assemblages in this marine province, as well as a priority area for conservation at the national and international level.