A sample of 1535 individuals of Elops saurus Linnaeus, 1766, from Ciénaga Grande de Santa Marta (CGSM) and the adjacent sea was examined between February 1987 to January 1988 and May 1990 to February 1992. The main meristic and rriorphometric aspects of the species, as well as the size frequency, are presented. The Lenght-Weight relationship obtained was TW= 2.7399*10-ÿLT5 Q931, and the average condition factor K was 4.74. It was determinated that 96% of the sexed individuals were inmature and sexually undifferenciated and that the female-male ratio was 1.5:1. The smallest mature females collected was 520 mm in TL. We conclude that juveniles live in the CGSM and the adults in the sea, where spawning probably takes place during the whole year. Fecundity was estimated in 519400 eggs for 950 mm TL female. Stomach contents analysis suggest that the main component of the diet are engraulidids fish and penaeids shrimp. Some differences were detected in the diet in relation with seasons and size. The permanent capture of juveniles in the CGSM must be controlled in order to protect the population and avoid further unbalance in the fisheries and the ecosystem.