Estrutura de assembleias de peixes demersais costeiros nos trópicos

Abstract

Determine the patterns of distribution of species are fundamental in ecology and conservation biology. For local communities,was demonstratedthat processes acting at spatial and temporal scales. That affects local characteristics, such as habitat structure, biotic interactions and environmental filters. For marinedemersalfish from shallow waters, the current distribution patterns reflect evolutionary adaptations and responses to environmental changes such as bathymetry,oceanographyfeatures and fishing. In this context, the aim was understand how different coastal formations (presence of reefs, coastal lagoons and river mouth) and different environmental variations (chlorophyll and turbidity) interact and affect occurrence patterns of demersal fishes in tropical coastal. So, experimental fishery using gillnets in the Northeast coast of Brazil was performed during a year. It were performed two local sampling at dry season (January to April) and two at rainy (May-July).Sampleswere takenin sixtransectsperpendicular to the coastline, with three sampling stations byisobath(10, 20 and 30 meters), totaling 18 sampling sites. To catch the fish was used a group of gillnet composed of 14 gillnet with 100 feet long by 2 wide, with internodes distances of 35, 40, 50, 60, 70, 80 and 90 mm. Turbidity and chlorophyll were recorded (nephelometric turbidity unit - NTU, mg / L ) at each site. The results indicated similarity at species richness and density for different depths (P> 0.05) in tropical coastal region. However, the difference in seabed complexity (defined as the proportion of reefs) were significantly different (P<0.05), acting in species composition, especially at shallow water depths. Regional factors (depth, seasonality) indicate greater relationship with turbidity (P<0.05) than chlorophyll (P> 0.05). Nevertheless, all variables (depth, period, region, chlorophyll and turbidity) affect the rate of species composition (P<0.05). Therefore, it is concluded that in tropical regions, understanding the species composition is more relevant than general data of abundance and species richness. So, it is still required more studies about topics such as functional, ecological, genetic and evolutionary characteristics.