The damming of rivers to generate electric energy is among the main anthropogenic impacts on rivers and their ichthyofauna. One of the main impacts of the construction of hydropower plants is the interruption of the migration of rheophilic fish, affecting their reproductive activity. Studying fish reproductive activity through ichthyoplankton generates relevant information for conserving fishery resources in dammed rivers. The aimed study was to estimate the ichthyoplankton density and the spawning areas of migratory fish downstream of the Urrá hydropower plant (UHP) in the Sinú River (Córdoba, Colombia).
Between April and October 2022, ichthyoplankton was collected at four sites downstream of the Urra hydroelectric plant (UHP): Aguas Prieta Spout and Cotocá Abajo (Lorica, Córdoba, Col) and Grande Spout and Bonanza (San Bernardo del Viento, Córdoba, Col). Sampling was carried out daily, three times a day (00:08, 12:00 and 16:00 hours) between April and October. Spawning areas were estimated considering the ichthyoplankton’s age and the river’s weighted velocity. The presence of ichthyoplankton in Aguas Prietas Spout, Cotocá Abajo, Grande Spout and Bonanza suggests fish reproductive activity from April to August.
The higher density of ichthyoplankton in all sampling sites was estimated in April, and the lower densities were recorded between May and August, while in September and October, no ichthyoplankton was collected (Table 1). The fish spawned between 7.9 km and 84.3 km downstream of the UHP. However, the amount higher events of spawning (67.1%) occurring between 20.3 km and 50.1 km downstream of the UHP of migratory species such as Prochilodus magdalenae, Megaleporinus muyscorum, Sorubim cuspicaudus, Pimelodus yuma, Brycon sinuensis and Salminus affinis.
The results suggest that the 2022 fish reproductive season began on April 9th and extended until August 4th. April showed a higher density of ichthyoplankton and was the month of greatest reproductive activity of migratory fish. The most important spawning area downstream of the UHP for migratory fish is between 20.3 km and 50.1 km downstream of the UHP.