fish composition was sampled in mar muerto lagoon (mexico) between 1991 and 1993. a total of 27 971 fish with a weight of 120.9 kg were collected. the total sample consists of 29 families, 45 genera and 66 species. the highest number of species is in the area with strong marine influence (near tonala inlet), abundant coastal vegetation and fluvial discharge. the lowest number of species is in the inner part of the lagoon, which is hipersaline in the dry season and of low salinity in the rainy season. the species with broad distribution are diapterus peruvianus, lile stolifera, anchoa lucida, anchoa mundeola, mugil curema, atherinella guatemalensis and anchovia macrolepidota.