Trophic ecology and reproductive biology of Ageneiosus lineatus (Actinopterygii, Siluriformes, Auchenipteridae) in the middle Negro River, Brazilian Amazon

Ageneiosus lineatus Ribeiro, Rapp Py-Daniel et Walsh, 2017 is a medium-sized catfish widely distributed in the Amazon and Orinoco basins. Despite its ecological relevance and potential in the ornamental fish trade, little is known about its biology. This study aimed to describe the feeding ecology, reproductive traits, and population condition of the species in the middle Negro River. Standardized sampling was conducted in three hydrological periods between 2016 and 2019, resulting in 164 individuals analyzed. The species showed predominantly nocturnal activity, a carnivorous diet with strong piscivory tendency (AI i > 94% in females). Females reached larger sizes than males, although males matured at slightly smaller lengths. The wide size range (7.50–18.0 cm) and condition factor ( K n > 1) indicate a healthy population. Although gonadal activity was recorded during high water, the limited sampling intervals prevented inference on reproductive seasonality. These findings highlight the ecological role of sedentary Amazonian catfishes and reinforce the need to incorporate them into adaptive management and conservation strategies.