Fish assemblage structure in a port region of the Amazonic coast

The fish assemblage structure in a port area in Sao Marcos Bay ( Amazon ic  coast)  was evaluated  based on the spatial and temporal distributions to identify potential changes in response to anthropic pressure increases associated with industrial and port activities in region. The samples  were taken  between March 2011 and Novemb er 2015. The  ichthyofauna  was represented by  a total of 56  species, distributed in 15 orders and 29 families. Captures  were dominated  by  Genyatremus luteus , but  Sciades proops  was the most representative in terms of biomass.  Seasonal distri butions of fish assemblage did not reveal significant differences. However, there was a difference between catch sites, abundance, biomass and Shannon diversity index was higher in the Site 1 and evenness in Site 4. The analysis NMDS and the test ANOSIM be tween months and between sampling sites, based on species composition, revealed a  seasonal  differentiation associated with the rainy and drought months , as  well as  spatial differentiation , in  function of  a  depth gradient and hydrodynamics ,  resulting from g reater distance from  mangrove  areas . The low diversity recorded may be a reflection of port activities that historically occur in the area investigated. However, there was still a maintenance of regional diversity throughout the period under analysis. Thus, temporal and spatial scales becom e important for the detection and understanding of fish biodiversity in an Amazonian estuary, reflecting,  the  importance of mangroves for the maintenance of the  ichthyofaunistic  diversity in the area. In this context,  the present study may  subsidize possible conservation projects in the area since information of this nature is almost non - existent for estuarine fish from the  Maranhao  Amazon.