Diversity of a Teleoste Fish Assembly in a Mangrove, São Luís Island, Maranhão, Brazil

2. Universidade Estadual Paulista, Brazil

Abstract: This study addressed aspects of the fish community present in a mangrove, on the island of São Luís, Maranhão, Brazil; covering composition and diversity. Species diversity analysis was based on the Simpson Index (D), because it gives greater weight to common species and the Shannon Index (H '), because it gives greater weight to rare species. For species richness analysis, which is a measure of diversity importance, the Margalef index was chosen. Regarding uniformity, or evenness, in the distribution of individuals among species, which corresponds to the maximum possible diversity for a given number of individuals N in the total of existing species; when the N individuals are distributed as evenly as possible among the s species, the Simpson Equitability and Shannon Equitability indices were used. Sampling was monthly for 16 months. The fishing tackle used was a gillnet fishing. 10.824 individuals were collected, including 63 species in 27 families. Margalef's wealth index ranged from 4.48 to 9.80; Simpson diversity between 0.63 to 0.87; Shannon diversity between 1.52 to 2.45; Simpson equitability between 0.66 to 0.91 and Shannon equitability between 2.20 to 3.50. Through the application of nonparametric Mann-Whitney test there was no significant difference between these indices in the dry and rainy seasons. The diversity observed in Raposa mangroves should not only be attributed to the nutrient input that is normally higher in mangroves, because this does not mean direct influence on diversity or richness, but on biomass. Probably this fact occurred due to the foraging behavior of the ichthyofauna, both species that seek food in the bottom substrate and those that feed on organisms that are in the water column. Then the difference may be in the availability of resources of this environment, also including protection from predators.