Condições ambientais e morfológicas na modulação do canibalismo em larvas de Brycon amazonicus

Abstract

This thesis evaluated how environmental and morphological conditions modulate cannibalism in matrinxã larvae, Brycon amazonicus, a native Amazonian species with high ecological and economic relevance for regional aquaculture. The research was organized into three complementary chapters. The first chapter presents an integrative comparative review of cannibalism and aggressive behavior in cultured Brycon species, showing that available evidence is concentrated in a small number of species, especially B. amazonicus, and that the onset of exogenous feeding is a critical window for cannibalistic interactions. The second chapter develops a morphometric predictive model to estimate the maximum size of conspecific prey that B. amazonicus larvae are able to ingest, based on the relationship among total length, body depth and maximum mouth opening. The model indicated that cannibal larvae can ingest prey ranging from 92 to 106% of their own total length, demonstrating high predatory capacity during early ontogeny and no evident morphological limitation within the analyzed interval. The third chapter evaluated the effect of different light spectra on ontogeny, survival, body cortisol and intraspecific predation in B. amazonicus was evaluated. Darkness delayed the development of some morphological structures, but increased survival and reduced stress, whereas red light was associated with higher mortality. Overall, the findings indicate that cannibalism in B. amazonicus should be understood as an ontogeny-driven, morphologically favored and environmentally modulated process. Therefore, strategies such as appropriate first-feeding management, prey-size compatibility, size grading and light control may reduce larviculture losses, improve animal welfare and support more sustainable production systems in the Amazon.