Diet and reproduction of the abotoado catfish, Pterodoras granulosus (SILURIFORMES, DORADIDAE): an invasive species in the middle-upper reaches of the Teles Pires River, Southern Amazonia, Brazil

Abstract

Belonging to the order Siluriformes and the family Doradidae, the granulated catfish (Pterodoras granulosus) has become an invasive species in the middle-upper Teles Pires River region after the removal of the natural barrier formed by the Sete Quedas waterfall for the implementation of the Teles Pires Hydroelectric Power Plant dam, in northern Mato Grosso, Brazil. This study investigated the feeding and reproductive dynamics of P. granulosus in the Teles Pires River. Twenty-seven specimens were captured during December 2021 and February 2022 (flood) and April and May 2022 (ebb) in the area of influence of the Sinop Hydroelectric Plant, of which eighteen were male and nine were female. The fish were euthanized and biometry, removal and fixation of the digestive tract and gonads were performed at the Tropical Ichthyology Laboratory, for further analysis. The gonads were classified macro and microscopically according to their reproductive stages. Stomach contents were analyzed using the frequency of occurrence method, and relative volume and food index (FIi) indicators. In terms of reproductive biology, in December 2021 the specimens were in the gonadal development phase, and in May 2022 in the regeneration phase. The P. granulosus specimens displayed isometric growth (b = 3.028; r²=0.829; p=6.79e-10). The most common items in the diet of the species were: fragmented leaves (FIi 52.48%), bivalves of the species Corbicula fluminea (FIi i 15.88%) and seeds (FIi 14.17%). From the results obtained, it can be inferred that the breeding period for this species coincides with the flood season in the basin, and that its feeding habit is omnivorous, with a tendency towards herbivory.