Dynamic energy budget modeling reveals reproductive collapse of an Amazonian catfish under dam-induced environmental change

• Energy budget modelling links flood pulse to fish life history shifts. • Lower food availability constrains growth, delays puberty, reduces egg production. • Fish adapts to post-dam conditions by increasing energy allocation to reproduction. • Fish reproduction collapses below critical food availability levels. • Model projections help assess dam impacts on tropical river fishes. In this study, we evaluated the effect of flood pulse alteration caused by the Belo Monte dam on a population of the catfish Tocantinsia piresi in the Volta Grande region of the Xingu River, Brazilian Amazon. We developed a Dynamic Energy Budget (DEB) model and simulated multiple scenarios combining temperature and food availability to assess their influence on the growth and reproduction of T. piresi . Model simulations were calibrated and validated using the Add-my-Pet method, incorporating empirical, field, and literature-based data. While increased temperatures had some effect on lifehistory traits, reduced food availability was the main driver of changes, leading to decreases in puberty size, ultimate body size, egg size and an increase in puberty age. Under severe food limitation ( f = 0.6), the model predicted failure to reach maturity and complete reproductive cessation. To better match empirical observations, we tested an adaptive scenario involving reduced allocation to somatic maintenance (lower), which improved model performance under post-dam conditions. Our findings highlight the strong influence of altered flood regimes on the metabolic and reproductive traits of Amazonian fishes and demonstrate the utility of DEB modeling in evaluating the ecological impacts of hydropower projects. We recommend incorporating DEB models into environmental impact assessments and conservation strategies for Amazonian ichthyofauna, especially in areas affected by existing or planned river dams.