Variação sazonal na diversidade da ictiofauna em uma área de influência do reservatório do rio Praquiquara, médio Apeú, Amazônia Oriental

Abstract

The ichthyofauna of the Amazon basin comprises about 1,400 freshwater species. However, knowledge about the diversity of this fauna is still incomplete, there is a shortage of data that presents its characteristics, composition and annual variations. In the present study, we bridge this gap by evaluating the influence of seasonal variation on the composition of the ichthyofauna of the Praquiquara watershed, Médio Apeú, Amazonia Oriental. Monthly collections were carried out during the period from July 2017 to June 2018, using gillnet and cast net at collection points. A total of 592 fish were collected, distributed in four orders, 11 families and 32 species. The orders Characiformes and Perciformes as well as the families Cichlidae and Characidae showed to be more abundant during the period of work. The percentage similarity analysis between station groups (SIMPER) identified the species Geophagus proximus, Heros efasciatus and Metynnis guaporensis for the dry period and the species Bryconops giacopinii, Geophagus proximus, Metynnis guaporensis and Hoplias malabaricusfor the rainy season as indicator species for the studied area. Analysis of the trophic structure of the community highlighted omnivorous species as the main food mode. Based on the collected data the following ecological indices were calculated: (1) Taxonomic diversity was calculated using the Shannon diversity index (H' = 2.909), (2) species richness was estimated using the Margalef index (d = 4.854) and (3) the equitability that describes the homogeneity of species distribution within a community was evaluated using the Pielou equitability index (J ' = 0.8394). To evaluate the seasonal influence between the dry and rainy season, multivariate statistical analyzes were performed. The analysis of similarity (ANOSIM), non-metric multidimensional scaling (nMDS) and hierarchical clustering (CLUSTER) showed that seasonal variation does not differentiate between abundance, richness and species diversity for the micro basin. Although there was no distinction between the studied periods (multivariate analysis), the study found some characteristics for each period, such as the increase of absolute abundance during the rainy season. The studied locality presented patterns different from those proposed for neotropical regions regarding their structure, fact that comes from the environmental modifications occurred from the implantation of a local reservoir. Data presented in this work are of great value for the knowledge of the Amazonian ichthyofauna, in addition to serving as a basis for maintenance plans of the local ichthyofauna.