Seasonal variation in the composition and abundance of mojarra species (Teleostei: Gerreidae) In a mangrove ecosystem in the gulf of California, México

Seasonal variation in the composition and abundance of a guild of seven gerreid species: Diapterus brevirostris (Sauvage, 1879), Eucinostomus currani Zahuranec, 1980, Eucinostomus entomelas Zahuranec. 1980, Eucinostomus gracilis (Gill, 1862), Eucinostomus dowii (Gill, 1863), Eugerres lineatus (Humboldt, 1821), and Gerres cinereus (Walbaum, 1792) was examined in order to assess the effect of the hydrological dynamics of El Conchalito estuary, a mangrove swamp ecosystem located in the southern Gulf of California. Monthly samples were collected from June 1996 to August 1997 using a stationary flume net deployed across the tidal channel. Densities were recorded for each species, as well as the standard length and weight of each individual. Hydrological parameters (water temperature, salinity, tidal level and dissolved oxygen) were measured in situ during each sampling event. The most abundant species in terms of density was D. brevirostris (62.6 %), while E. entomelas was the most prevalent species in terms of biomass (34.6%). A significant correlation was found between temperature and species abundance (including E. currani). Seasonal environmental variability in the ecosystem prompts changes in the composition and abundance of gerreids; the high incidence of juveniles during summer and winter highlights the importance of this ecosystem as a nursery for fish fauna.