Diapterus rhombeus dominates the nektonic community of Terminos Lagoon and is associated to zones with submerged vegetation, temperatures between 27 and 33°C and salinity between 25 and 36.5 UPS. A total of 3 024 individuals were collected with a trawl net in 23 sites between September 1997 and September 1998. The length-weight model parameters are a = 0.0098; b = 3.155 with a 96% correlation. The growth parameters are L∞ = 20.4 cm, k = 0.74 and to = - 4.207 and the total mortality coefficient is 3.526. Fish length is 2.5 - 18.0 cm with a mode of 7.5 cm. Recruitment is continuous with a peak from May to August. The species uses several habitats of the lagoon mainly for feeding and growth, reproduction probably occurs in the adjacent continental shelf. Movements between continental shelf and the estuarine system represent a continuous energy flow
Keywords: Diapterus, rhombeus, Gerreidae, Terminos lagoon, fish growth, abundance, distribution