Changes in the taxonomic diversity of the reef fish community of San José Island, Gulf of California, Mexico

Although San José Island is considered one of the most important islands in the lower Gulf of California due to its commercial fishing activities, few studies have evaluated their fish taxonomic diversity. The aim of this study was to determine the variation in the taxonomic diversity of the conspicuous fish community in eight locations around San José Island from March 2001 to February 2002. We assessed the changes in the diversity of rocky reef fish based on the taxonomic distances between species, using Fisher's alpha diversity index, average taxonomic distinctiveness (AvTD Δ+), and taxonomic distinctiveness (Δ*). Visual censuses were conducted in 48 transects consisting of 100 × 5 m quadrants (500 m² sampling area) at an average depth of 5 m, from 09:00 to 16:00. A total of 26,608 fishes belonging to 112 species and 76 genera were found. The index of relative abundance was used to determine the most important species, which were in order of abundance: Abudefduf troschelii, Thalassoma lucasanum, Stegastes rectifraenum, Mulloidichthys dentatus, Chromis atrilobata, Lutjanus argentiventris, and Scarus ghobban. According to Fisher's alpha diversity index, the highest diversity of species was found in July and the lowest in February. The indices of Δ+ and Δ* indicated significant temporal and spatial differences.