Como a dieta influência na atividade reprodutiva de Characideos em riachos Amazônicos? Um estudo de caso do tetra-bandeira Hyphessobrycon heterorhabdus (Characiformes: Characidae).

Abstract

The present study aimed to analyze the relationship between the feeding ecology of Hyphessobrycon heterorhabdus and the seasonality of its reproductive activity in streams in the Eastern Amazon. Collections were carried out bimonthly from March 2019 to January 2020 in three streams using sieves. Captured fish were euthanized, fixed in formalin in 10%, and preserved in 70% alcohol. In the laboratory, the standard length (SL), total weight (Wt), and stomach weight (Ws) of the specimens were measured. Gonads were weighed (Wg) and stored. Food items were then identified to the lowest taxonomic level and grouped into 19 food categories. Each category was evaluated for its Relative Volume (V%) and Frequency of Occurrence (FOi%), which were combined to obtain a Dietary Importance Index (IAi%). The feeding intensity of H. heterorhabdus was evaluated using the Stomach Replenishment Index (SRI%). The reproductive activity of H. heterorhabdus was assessed using the Gonadosomatic Index (GSI). GSI values were compared between months, separately for males and females, using the Kruskal-Wallis test and Wilcoxon multiple comparison test. The GSI was correlated with the dietary importance of the three most important categories in the species diet and dietary intensity through Spearman survey analysis. This correlation was also performed considering the GSI of a given month and the importance of the categories two months before and two months after. A total of 81 adult males and 56 females were sampled, which showed reproductive activity throughout the months, with a greater intensity between March and May 2019. The diet of H. heterorhabdus was predominantly composed of allochthonous insects, with more evident seasonal variations in the consumption of Diptera and Formicidae larvae and pupae. The Stomach Replenishment Index (SRI%) varied significantly between months, with higher feeding intensity in March. The spearman demonstration showed a significant relationship between male reproductive activity and feeding intensity in the same month. These results reinforce that diet of H. heterorhabdus may not be the main predictor of reproductive activity, which in turn may be predominantly influenced by variations in the availability of spawning microhabitats, formed mainly in periods of greater local variations.