Distribuição dos peixes nos estuários do nordeste brasileiro de acordo com a salinidade da água

Abstract

The chief purpose of this study is to get facts on the relationships of the estuarine fishes, to natural water salinity. This study is on the basis of the data collected during the years 1966 to 1976 in several estuaries of the northeast Brasil, from the Ceará State to Sergipe State. An inventory of the fishes collected and a small study on the salinity gradiant in these estuaries were also made, including data found in the references. A total of 158 species are refered, and only two species are of the Class Elasmobranchii . On the basis of the 142 species studied, the fishes of the estuaries of the northeast Brazil were placed into 5 ichthyofaunistic components: fresh water, oligohaline, marine stenohaline, marine euryhaline and complet euryhaline. The freshwater component, comprises a few salt-tolerant species derived from the rivers and found in salinities below 15° /oo. The oligohaline component, those species with marine affinities restricted to estuaries but tolerating freshwater. The marine stenohaline component, includes those species derived from the sea and do no penetrate into estuaries below salinities of 25° /oo. The marine euryhaline component comprises those species derived from the sea and tolerate salinities below 25° /oo. The complet euryhaline component are those species that inhabit both pure freshwater and salt water indifferently. There is a relationship between water salinity and the number of species: the number of marine species decreases with decreasing salinity, the contrary being true of freshwater species, on the other hand, the number of oligoaline species is practically stable in the recorded salinity levels. Also, there is a predominance of the marine species, even in the low salinities.