Hindawi Publishing Corporation Journal of Marine Biology Volume 2013, Article ID 176760, 17 pages http://dx.doi.org/10.1155/2013/176760 Research Article Fish Larvae Response to Biophysical Changes in the Gulf of California, Mexico (Winter-Summer) Raymundo Avendaño-Ibarra, 1,2 Enrique Godínez-Domínguez, 1 Gerardo Aceves-Medina, 2 Eduardo González-Rodríguez, 3 and Armando Trasviña 3 1 Departamento de Estudios para el Desarrollo Sustentable de la Zona Costera, Centro Universitario de la Costa Sur (CUCSUR), Universidad de Guadalajara, Avendia V. G´ omez Far´ ıas 82, 48980 San Patricio Melaque, JAL, Mexico 2 Instituto Polit´ ecnico Nacional, CICIMAR-IPN, Departamento de Plancton y Ecolog´ ıa Marina, 23096 La Paz, BCS, Mexico 3 Centro de Investigaci´ on Cient´ ıica y de Educaci´ on Superior de Ensenada, Unidad La Paz, 23050 La Paz, BCS, Mexico Correspondence should be addressed to Raymundo Avenda˜ no-Ibarra; ravendan@ipn.mx Received 17 April 2013; Revised 1 July 2013; Accepted 4 July 2013 Academic Editor: E. A. Pakhomov Copyright © 2013 Raymundo Avenda˜ no-Ibarra et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We analyzed the response of ish larvae assemblages to environmental variables and to physical macro- and mesoscale processes in the Gulf of California, during four oceanographic cruises (winter and summer 2005 and 2007). Physical data of the water column obtained through CTD casts, sea surface temperature, and chlorophyll a satellite imagery were used to detect mesoscale structures. Zooplankton samples were collected with standard Bongo net tows. Fish larvae assemblages responded to latitudinal and coastal- ocean gradients, related to inlow of water to the gulf, and to biological production. he 19 ∘ C and 21 ∘ C isotherms during winter, and 29 ∘ C and 31 ∘ C during summer, limited the distribution of ish larvae at the macroscale. Between types of eddy, the cyclonic (January) registered high abundance, species richness, and zooplankton volume compared to the other anticyclonic (March) and cyclonic (September). hermal fronts (Big Islands) of January and July afected the species distribution establishing strong diferences between sides. At the mesoscale, eddy and fronts coincided with the isotherms mentioned previously, playing an important role in emphasizing the diferences among species assemblages. he multivariate analysis indicated that larvae abundance was highly correlated with temperature and salinity and with chlorophyll a and zooplankton volume during winter and summer, respectively. 1. Introduction he biological-physical interactions in the oceans play an important role in determining patterns of horizontal distribu- tions of the plankton communities [1], and these interactions occur at a wide range of temporal and spatial scales [2], being the mesoscale processes such as fronts, eddy, and upwelling, the most determinant factors in the spatial distribution and structure of the zooplankton communities on basin and local scales [3]. Mesoscale oceanographic structures such as eddy and fronts can work as mechanisms of retention and concen- tration of ish larvae [4–11], and upwelling ilaments, includ- ing eddy, may work as mechanisms of dispersion [12–17]. he Gulf of California is a semienclosed dynamic sea where strong changes in temperature, salinity, and currents [18] are related to the seasonal lux of the Gulf of California and to tropical surface water masses which provide a unique environment where the southern tropical, subtropical, and northern temperate marine biota develops [19, 20]. he northern region has an anticyclonic circulation most of the year, while in June and September it reverses to a cyclonic eddy [21]. Strong winter upwelling is present in the continen- tal coast, while during the summer it is weak at the peninsular coast [18]. hree to ive alternated eddy and jet streams [22, 23] have been registered from south of the Big Islands to the south o the gulf with a markedly seasonal component. All these dynamic features may promote a wide diversity of responses of the ish larvae community to the environment. It has been shown that the ichthyofauna distribution in the Gulf of California responds to a latitudinal gradient: (a) temperate species are more abundant to the north, (b) tropical ainity species are more abundant to the south, and