Assembleia de peixes de estuários negativos do Nordeste brasileiro: atualização taxonômica, padrões espaço-temporais e aspectos funcionais

Abstract

Estuaries has high fish species richness that respond to environmental conditions in different ways. This study aimed to survey the ichthyofauna occurring in the Choró, Curu, Pacoti and Pirangi estuaries (Ceará-Brasil); test the hypothesis that the fish assemblages change among estuarine zones, among periods of the year and among estuaries; test the morphological patterns of fish assemblage under the hypothesis that different morphological attributes suggest different forms of resources exploitation; and test the trait-environment relationship of fish assemblage along the estuaries. In the years 2014 and 2015 fish samples were taken in the main channel of the estuaries with seine and cast net. Abundances, biomasses and classification of fish species by use the estuarine environment, trophic and position in the water column guilds were obtained. Salinity and substrate type were measured. Fifteen functional traits related to ecological characteristics as the habitat use, locomotion and diet were obtained. Temporal and spatial variations in the species, families and guilds compositions were plotted with non-metric multidimensional scaling (NMDS). To verify the fish assemblages differences were performed PERMANOVA. Species, families and guilds with emphasis on the separation of the groups were identified using percentage of similarity analysis (SIMPER). Principal component analysis (PCA) assessed trends in interspecific variation in the fish assemblage. The null hypothesis that the morphological patterns of fish species are independent of the groups formed by the guilds was tested using PERMANOVA. With the rejection of the null hypothesis, canonical discriminant analysis (CDA) evaluated the ecomorphological relations. It conducted double inertia RLQ analysis to verify the relationship among the functional traits and the habitat structure. The statistical significance among the functional traits and habitat structure was assessed by permutation tests with the null models 2 and 4. Fourth-corner analysis details the RLQ patterns to determine the significance of bivariate associations. A total of 104 fish species were collected in the four estuaries, representing 19 orders and 45 families, with few species dominating in abundance or biomass and 96 new reports. The most representative guilds in number of species were marine, followed by the estuarine and freshwater guilds. The Curu estuary presented different abundances of species. The Choró, Curu and Pacoti estuaries showed distinct taxonomic and functional abundances among their zones. The estuaries did not change the fish composition temporally. The morphology of fishes explain in part the use of resources. Estuaries were homogenous regarding the distribution of fish functional traits, so that the habitat characteristics did not act in functionally select the assemblage composition. Taxonomic metrics were efficient in showing patterns, but the functional metrics also provided comparisons of the estuarine fish fauna components. This study presents new reports of fish species to estuaries from Ceará state and shows spatio-temporal patterns for three negative estuaries of northeastern Brazil with taxonomic and functional approaches.