Estructura comunitaria de peces, asteroideos y equinoideos en el Farallón de San Ignacio, arrecife situado en la “brecha faunística de Sinaloa”, México

Abstract

Even though there is extensive research on the rocky reefs in the Gulf of California, some areas still have scarce information, such as the Farallón de San Ignacio, which is well known for its high biodiversity and its location in the biogeographic transition zone known as the "Sinaloa gap." Due to the limited information available for this site, the present study aimed to describe the composition and structure of asteroid and echinoid fish assemblages at the Farallón de San Ignacio. For this purpose, visual surveys were conducted in November 2016 using belt transects of 25 m long by 4 m wide for fish and 25 m long by 2 m wide for invertebrates, to estimate species abundance, richness, diversity, and evenness indices, and to compare them with other rocky reefs located at the same latitude on the western coast of the Gulf of California that were visited the same year. A total of 34 species were recorded, including two asteroids and four echinoids. The most abundant species were the fish Azurina atrilobata, the starfish Phataria unifacialis, and the sea urchin Diadema mexicanum. Despite the Farallón’s isolation, the complexity of its community structure is similar to that of other islands in the Gulf of California, although there were differences in species composition due to the high abundance of herbivorous species at this site.