Ecological surveys from several coastal environments in Bahía de La Paz were analysed to determine the seasonal changes in the fish assemblages in the largest bay of the Gulf of California. We identified 58 species from 37 genera and 23 families in seasonal gill net samples were taken over 1 yr. Using the relative abundance index (%N), the most important species were Gerres cinereus, Arius platypogon, Lutjanus guttatus, Haemulon sexfasciatus, Kyphosus elegans, Diapterus peruvianus, Chaetodipterus zonatus, and Nematistius pectoralis. By relative weight (%W) the main species were similar but in a different ranking Kyphosus elegans, L. guttatus, G. cinereus, A. platypogon, Carcharhinus porosus, H. sexfasciatus, and Scomberomorus sierra. Three seasonal species groups were determined and their abundance, richness, and diversity were analyzed. Dissimilarity analysis suggests that were closely three habitats associated with three different fish assemblages inside Bahia de La Paz: (a) an exposed coastal zone with big rocks and sandy beaches; (b) protected coastal estuarine zone with sandy and shallow bottom; and (c) an oceanic island zone with rocky bottom and sandy patches
