Estrutura populacional, reprodução e dieta de Gymnogeophagus taroba (Casciotta, Almirón, Piálek & Říčan, 2017), espécie endêmica de uma ecorregião Neotropical

Abstract

The Iguaçu River basin is considered a freshwater ecoregion due to the high degree of endemism of its ichthyofauna. Gymnogeophagus taroba is an endemic, small species and studies on its bioecology are scarce. Thus, the aim of the study was to characterize the population structure and feeding habits of G. taroba. Collections were carried out monthly from January 2010 to January 2011 and from September 2012 to December 2016, in the Lower Iguaçu River region, covering areas within the Iguaçu National Park (INP) and anthropized areas outside the INP. In all, 802 specimens were analyzed, with total length and weight ranging from 1.5 to 15 cm and from 0.02 to 51.90 g, respectively. The sex ratio did not show significant differences for the population and the largest length classes contained only male individuals. The weight-length relationship for both sexes exhibited isometric growth. The reproductive period established through the average variation of the Gonadal-Somatic Index (GSI) and frequency distribution of males and females encompassed between August and February, with reproductive peaks in September and November for females and in October for males. The size of the first gonadal maturation (L50) corresponded to 6.03 cm for males and 4.15 cm for females. The analysis of the frequency of degrees of repletion by periods (morning, afternoon and night), reveled greater feeding activity during the night. The feeding habit of the species, determined through the Index of Feeding Importance (IFI), was characterized as a benthic insectivore, with emphasis on the consumption of larvae of Chironomidae and Trichoptera. The study provides unprecedented information about certain parameters of the population structure, reproduction and feeding habits of G. taroba, which will assist in effective conservation actions for the species.