Variation in the diet composition and weight-length relationship of small characids in urbanized and forested streams.

The diet of indicator fish species plays a crucial role in assessing ecosystem health. This study evaluated streams with and without urban influences, focusing on abiotic parameters and the trophic ecology of Psalidodon fasciatus and Piabina argentea. Forested streams exhibited higher redox potential, dissolved oxygen, transparency, and depth, whereas urban streams had higher temperatures, greater widths, and increased levels of total dissolved solids, conductivity, total coliforms, and thermotolerant coliforms. The P. fasciatus population exhibited isometric growth in forested streams and negative allometric growth in urban streams. Conversely, P. argentea exhibited negative allometric growth in both types of environment. The diets of both species included items of autochthonous and allochthonous origin. P. fasciatus had a similar diet in both stream types, whereas P. argentea's diet varied significantly between forested and urban streams. These findings highlight the importance of understanding the interplay between environmental characteristics and species diets, offering crucial insights into the health status of streams, especially those impacted by urbanization.