ORIGINAL PAPER Changes in the taxonomic diversity of the reef fish community of San Jose ´ Island, Gulf of California, Mexico Emelio Barjau-Gonza ´lez • Jesu ´s Rodrı ´guez-Romero • Felipe Galva ´n-Magan ˜a • Juana Lo ´pez-Martı ´nez Received: 26 January 2012 / Accepted: 21 September 2012 / Published online: 27 September 2012 Ó Springer Science+Business Media Dordrecht 2012 Abstract Although San Jose ´ Island is considered one of the most important islands in the lower Gulf of California due to its commercial fishing activities, few studies have eval- uated 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 Jose ´ 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 D?), and taxo- nomic distinctiveness (D*). Visual censuses were conducted in 48 transects consisting of 100 9 5 m quadrants (500 m 2 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 rectifrae- num, 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 D? and D* indicated significant temporal and spatial differences. Keywords Conspicuous fishes  Fisher’s alpha diversity index  Gulf of California  Taxonomic diversity E. Barjau-Gonza ´lez  J. Rodrı ´guez-Romero  J. Lo ´pez-Martı ´nez Centro de Investigaciones Biolo ´gicas del Noroeste (CIBNOR), Apdo. Postal 128 La Paz, C.P. 23000 Mexico, BCS, Mexico E. Barjau-Gonza ´lez Departamento Acade ´mico de Biologı ´a Marina, Universidad Auto ´noma de Baja California Sur (UABCS), Apdo. Postal 19-B, La Paz, C.P. 23000 Mexico, BCS, Mexico F. Galva ´n-Magan ˜a (&) Departamento de Pesquerı ´as y Biologı ´a Marina, Centro Interdisciplinario de Ciencias Marinas (CICIMAR-IPN), Apdo. Postal 592. La Paz, C.P. 23000 Mexico, BCS, Mexico e-mail: galvan.felipe@gmail.com 123 Biodivers Conserv (2012) 21:3543–3554 DOI 10.1007/s10531-012-0378-z