Avaliação temporal da estrutura funcional da ictiofauna do reservatório Santo Anastácio, Ceará, Brasil

Abstract

Understanding how environmental changes affect ecosystems temporally requires considering the multiple characteristics of natural communities and the attributes of organisms. Functional characteristics of the taxa that compose communities favor the understanding of relationships between species and ecosystems. This approach can be visualized temporally in a single ecosystem under constant effect of environmental pressures such as eutrophication. Characteristics of the fish assemblage present in the Santo Anastácio reservoir, Ceará, were evaluated over a period of forty-two years (1977 to 2019). Through these studies, changes in fish assemblage from a functional approach were investigated. With the attributes of the individuals (morphological, physiological and behavioral) it was possible to evaluate the influence of ecosystem changes on the fish assemblage. Three articles published over a period of thirty-two years (1977, 1987 and 2009) were used to compare the taxonomic and functional richness of large-scale temporal fish species. For a smaller scale analysis, monthly comparisons of taxonomic and functional abundance and dissimilarity were performed, as well as the temporal variation in the β-functional diversity metrics of the assemblies. The collections were performed in a standardized way, using nets, trawls and fishing nets in the years 2009 and 2019. The collected fishes were identified to the lowest possible taxonomic level. Subsequently, information related to the composition, number of species and functional characteristics related to body structures, feeding, breathing and behavior of the ichthyofauna were used to identify temporal changes in the assembly. Composition and abundance changed temporally, with fish species less tolerant to disturbed environments being replaced by species more tolerant to eutrophication environmental conditions over time. Thus, the reservoir tends to lose fish diversity and increase the abundance of species that have similar functional traits and can survive in more eutrophic environments.