Abstract
1. Fish play a crucial role in nutrient recycling within various aquatic ecosystems, but how their contribution varies across streams with different levels of disturbance remains poorly understood.
2. In our study, we investigated the role of fish assemblage in nutrient cycling within eight Neotropical streams characterised by varying degrees of land use.
3. We found that fish were significant nutrient recyclers, excreting nitrogen and phosphorus at rates approximately 1.8‐ and 1.6‐fold higher, respectively, than the nutrient demand in these ecosystems. This contribution became even more pronounced in the forested, low‐nutrient streams. Notably, allochthonous insectivorous fish were dominant in these well‐preserved streams and played a primary role in nutrient excretion within the community. One particular, as yet undescribed species (Astyanax sp. n.) was found to excrete nitrogen and phosphorus at rates 2‐ and 2.9‐fold greater than the demand of the stream.
4. These findings underscore the critical role of fish as regulators of nutrient cycling and highlight the significance of specific key species in facilitating the transfer of nutrients from terrestrial to aquatic ecosystems.