Variação espaço-temporal de assembleias de peixes em poças de maré em manguezal

Abstract

Intertidal mangrove forests play important roles for especies persistence, providing food and shelter from predators for marine and estuarine small fishes. Despite the great progress in knowledge of estuarine and mangrove systems in the last decades, little is know about fish community dynamics in the temporary enviroments of mangroves. The present study aims for understand the fish species distribution on tidepools inside the mangrove forest along the estuary (spatial dynamics), between seasonal surveys (temporal dynamics) and according to microhabitat characteristics. Field work was conducted from november 2017 to september 2018 on the Ceará-Mirim river mangrove (Northeastern Brazil). We stabilished 17 10m x 10m quadrats distributed along the estuary, which were used as sample units. Our fish collection followed a standardized protocol during low tide. Physical-chemical and microhabitat variables (density of roots, ponds, crab burrows, propagules, canopy cover and pond number and depth) were mesured. 1189 individuals belonging to 10 species were collected. with Kryptolebias hermaphroditus being the dominant species (52% of total fish abundance), followed by Poecilia vivipara (24%), Ctenogobius smaragdus (11%), Ctenogobius shufeldti (2%), Ctenogobius boleosoma (2%), Evorthodus lyricus (3%), Dormitator maculatus (<1%), Eleotris pisonis (1%), Guavina guavina (4%) and Erotelis smaragdus (<1%). Abundance, richness and diversity was higher in the rainy months. P. vivipara and Gobiidae species followed this pattern, with major abundances in this period. K hermaphroditus and Eleotridae species were more constant along the year. We found a inverse relationship between diversity and abundance along the estuary, with major diversity and minor abundance occurring closer to de ocean, in constrast with upper areas with minor diversity and major abundance. P vivipara occured more in the upper areas of the estuary, while C. boleosoma and E. pisonis tended to occur closer to the ocean. Other species were more constant along the estuary. The different microhabitat characteristics within the mangrove forest were also important to species distribution. We found evidences that the fish assemblages in the mangrove forest are modulated by rainfall cycle, the closeness to the ocean and microhabitat characteristics. We discuss these findings in light of the current knowledge on mangrove fish.