Morphological and ecological approaches in reproduction of the endemic catfish of the eastern Amazon.

This study aimed to describe reproductive ecology based on morphological aspects of Peckoltia oligospila in stream rapids, eastern Amazon. A total of 186 fish (75 males and 111 females) were collected. The sex and gonadal maturity stage of these specimens were obtained based on histological characteristics of the gonads. The sex ratio, gonado-somatic index (GSI), relative frequency of the different maturity stages, size at first sexual maturation, condition factor of the population, and fluviometry were evaluated during the study. There was a significant female frequency during the study. The population exhibited positive allometric growth without differences between sexes. GSI and relative frequency showing a reproductive period synchronized in February, and the species exhibited parcelated spawning. L₅₀ was estimated at 5.85 and 7.39 cm for females and males, respectively. There were significant differences in the condition factor only in females that showed a highest value in August. Thus, based on the results P. oligospila has an intermediate strategy between the opportunistic and equilibrium strategies.