This paper contains a preliminary list of the fishes caught monthly during the period between March, 1982 and April, 1986, in the littoral of the São Luís Island, and estuarine region including the localities Cururuca, Paciência, Cachorros and Ana Jansen, and the straits Coqueiro/Mosquitos. 132 species belonging to 94 genera and 56 families were obtained. Salinity ranged between 1.0 - 37.5‰ at Cururuca and Paciência; 3.9 - 20.8‰ at Ana Jansen, and 1.0 - 32.7‰ in the area including Mosquitos/Coqueiro and Cachorros. No correlation between salinity and distribution of species was obtained. Genyatremus luteus was the predominant species (21.4%) followed by Mugil curema (11.6%) and Arius herzbergii (11.2%). Ariidae, Mugilidae, Sciaenidae and Engraulidae were the most representative families in number of individuals and species.