Efectos de la variabilidad climática y factores antrópicos sobre la reproducción de los peces migradores del río Sinú, aguas abajo de la hidroeléctrica Urra, Córdoba, Colombia

Abstract

This study evaluated the effects of climate variability and various anthropogenic factors on the reproduction of key migratory fish species in the Sinú River downstream of the Urrá Hydroelectric Power Plant during the 2001–2022 period. The research focused on four species of ecological and fisheries importance: bocachico (Prochilodus magdalenae), dorada (Brycon sinuensis), bagre blanco (Sorubim cuspicaudus), and barbul (Pimelodus yuma). Climate variability associated with the ENSO (El Niño–Southern Oscillation) phenomenon, combined with anthropogenic activities—such as hydroelectric dam construction, pollution, loss of connectivity between the river and wetlands, and overfishing—has altered the reproductive dynamics of these species. The Urrá Hydroelectric Power Plant fragmented the natural course of the Sinú River, modifying the hydrological regime and reducing migration and spawning areas. Ichthyoplankton data collected daily during the migratory fish spawning season (April to September) over a 22-year period (2001–2022) were analyzed. Environmental variables such as water temperature, ambient temperature, and flow rate were also evaluated. Non-parametric statistical tests (Shapiro-Wilk, Kruskal-Wallis, and Dunn) and the Random Forest machine learning algorithm were employed. Additionally, a spatial characterization of spawning areas was conducted using ArcGIS and the Herfindahl-irschman Index (HHI). The results suggest that flow rate was one of the environmental variables with the greatest influence on larval abundance. Analyses of ENSO revealed effects of the climatic phenomenon (6, 12, and 24 months post-ENSO) that showed significant differences in larval abundance—particularly during El Niño events—and were associated with decreases in larval abundance. Conversely, La Niña years showed higher larval abundances. These trends were observed across all four species evaluated, although the *dorada* exhibited the greatest sensitivity to environmental variations. Anthropogenic factors were analyzed through a review of records concerning the loss of lateral connectivity between the river and wetlands, the construction of roads and levees, sedimentation in waterways, agricultural and livestock expansion, and contamination by heavy metals and pesticides—all of which have degraded the quality of reproductive habitats. Concentrations of mercury, arsenic, cadmium, and lead were detected in sediments and fish, posing potential risks to fertility, embryonic development, and larval survival. Furthermore, overfishing and the harvesting of juveniles have depleted breeding populations and compromised the sustainability of the fishery. Spatial analysis revealed that the spawning zone extends from the Urrá Hydroelectric Plant to the Gallo Crudo sector, covering approximately 125.2 km downstream. A shift of the reproductive zone toward areas with superior environmental and water quality conditions was also observed. The study results lead to the conclusion that the reproduction of migratory fish in the Sinú River is determined by the interaction between climate variability and multiple anthropogenic pressures. The ENSO phenomenon indirectly influences larval abundance through changes in river flow and hydrological conditions, while river fragmentation, pollution, wetland loss, and overfishing reduce reproductive potential and threaten the sustainability of migratory populations. This study highlights the need to strengthen conservation measures, restore ecological connectivity, and improve environmental and fisheries management in the Sinú River basin.