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Diets of fish larvae may vary within populations and among species and are affected by larval prey availability and foraging capacity. We aimed to describe the diet of fish larvae based on empirical field observations, emphasizing the interaction and organization of the predator–prey network using Auchenipterus osteomystax as a species model. The network showed few interactions (low connectance and modularity) but a nested structure (some items that had fewer records tended to occur together with the most frequent ones), low complementary specialization (the proportions of ingested items tended to be equivalent) and a pattern of segregation (some items tended not to be consumed together) in the use of resources among individuals. Robustness was low when the removal of prey with a higher consumption frequency occurred. The correlation between morphological variables and network attributes was significant and positive for abundance and strength, while the correlation with nested rank was negative. The availability of suitable dietary resources is likely to be the key factor for success and survival in the early stages of development. With changes in morphology during larval development, A. osteomystax showed a generalist position in the network as its predation capacity increased. A new approach to trophic ecology studies of fish larvae incorporating network analysis may help explain the individual characteristics of larvae and assess the pattern of interactions in the population. [ABSTRACT FROM AUTHOR]

In order to investigate the reproductive dynamics of the ichthyofauna in the Brazilian Pantanal, this study examines the spatial and temporal distribution of ichthyoplankton, taxonomic composition, and its correlation with environmental factors within one of the most important sub‐basins, the Taquari River. Egg and larvae collections were conducted at 11 sampling points between October and March of 2017/2018 and 2018/2019. Significant differences were observed between collection points, months, and years, with higher ichthyoplankton densities in the Coxim and Taquari rivers, particularly between November and January. Twenty‐eight genera and/or species of fish were identified, including 10 long‐distance migratory species. Egg density showed a negative correlation with water temperature and rainfall. For larvae, water transparency and rainfall were both significant, negatively influencing larval abundance. However, different species tend to occur in environments with distinct abiotic qualities. Yolk‐sac, preflexion, and flexion larval development stages were distributed throughout the sub‐basin, especially near the Pantanal. Considering the data and analyses presented in this study, the importance of connectivity between these environments, specifically between the plateau and Pantanal, is evident, highlighting the significance of the entire sub‐basin for fish reproductive processes. Therefore, research focusing on the ecological processes influencing the distribution of ichthyoplankton offers valuable insights for ecosystem conservation and aids in effective environmental management. [ABSTRACT FROM AUTHOR]