Fish monthly samples were made in three tributaries and in the main stream in order to study population dynamics and the influence of flow on abundance of Agonostomus monticola (Mugilidae) and Brycon behreae (Characidae) in the basin of Térraba River Basin (Costa Rica). Flow was seasonal in these rivers, with peak flow in October. Recruitment was different among the species, B. behreae recruited from January to June and A. monticola all year round with a peak in June-July and October-November. Juveniles were more abundant in smaller streams. Abundance was higher in general during low flow and low turbidity periods. The results suggest that the streams have an important role in the maintenance of both species in the ecosystem, where juveniles can use the streams as nursing habitats during their development, allowing these small streams to be considered as essential fish habitats. Also, it was determined that the increased volume and turbidity of water can significantly affect the proportion of adults and juveniles between the main river and its tributaries.
Population dynamics; Fish recruitment; Environment conservation
