The main channel and river confluences as spawning sites for migratory fishes in the middle Uruguay River

Abstract Evidence indicates that migratory fish reproduce in the middle Uruguay River, but location of spawning sites remains unknown. To identify basin, eggs and larvae were sampled monthly between October 2016 January 2017. The sampling was carried out three sections along covering two environments: main channel mouth tributaries (Comandaí, Ijuí, Piratinim rivers). A total 11,519 3,211 captured, belonged to ten species. Eggs fishes, widely distributed, with predominance segmented eggs, yolk-sac pre-flexion stages, higher densities near confluence River. Larvae assemblages showed spatial variation, indicating differ among This study provides new information about reproduction revealing species spawn different localities tributaries. region may function as a critical site for reproduction, although it is currently threatened by risk hydropower expansion, emphasizing need measures preserve their environmental conditions, hydrological connectivity ecological functions.