Fish community turnover in a dammed Andean River over time

Abstract

We describe the change in the fish community of the Porce River in Magdalena River Basin, Colombia, following the construction of the Porce III hydropower reservoir based on 13 years of monitoring data. The results show a clear reduction of the number of native species, which have been supplanted by colonizing non-native species, especially in the reservoir. Four native species detected prior to dam construction have apparently disappeared, but 12 new species were registered post-construction. We analyzed spatial changes in beta diversity in the aquatic environments surrounding the dam. The new environment generated by the reservoir presents a unique species composition and contributes significantly to the total beta diversity of the system. Altogether three distinct new fish assemblages emerged following reservoir formation and there are now six assemblages where there had previously been three. This dramatic change, already visible within a decade of construction, highlights just how strong of an impact dam construction has on habitats and how rapidly fish communities react in this hotspot for endemic fish diversity. Our findings demonstrate the importance of monitoring fish communities for revealing the impact of damming on river ecosystems and informs potential complementary fish diversity inventories elsewhere in the Magdalena River basin.

Patterns and drivers of water quality changes associated with dams in the Tropical Andes

“…Because the data come from sparse grab samples, it is not clear how persistent hypoxia is in these river reaches, but, at minimum, they indicate a loss of viable habitat for hypoxia-sensitive species for at least some parts of the year. The fish communities downstream of Colombia's Porce III dam -one of the projects with hypoxic tailwater -have shifted, with a loss of some native species and replacement by invasive exotic species (Valencia-Rodríguez et al, 2022). The authors of this study attribute these shifts to habitat fragmentation, but anoxia/hypoxia could be an important factor, as many other studies have commented that the multiple changes and stressors imposed by dams are difficult to disentangle (van Puijenbroek et al, 2021;Young et al, 1976).…”

Rescate de peces aguas abajo de la presa Porce III (Colombia) para reducir su mortalidad

“…La distribución de las especies aguas abajo de la presa de Porce III es similar a la tendencia general de la riqueza de peces en los ambientes acuáticos del área de influencia del embalse (Valencia-Rodríguez et al, 2022). Los peces que quedan atrapados en pozas y no logran reincorporarse nuevamente al cauce principal del río incluyen principalmente especies de pequeño porte, pertenecientes a los órdenes Characiformes y Siluriformes, los cuales por su abundancia, y posiblemente por diversos aspectos ecológicos asociados al uso del hábitat, la locomoción y sus estrategias alimenticias (Conde-Saldaña et al, 2017), lleguen a colonizar los nuevos espacios provocados por el aumento temporal del volumen de agua, generado por la apertura de las compuerta del vertedero.…”

“…Estas modificaciones influyen en la distribución y diversidad de los peces en el área de influencia de estos nuevos ambientes (Álvarez-Bustamante et al, 2018). La formación del embalse genera nuevos ensamblajes dentro del mismo embalse, así como en los sistemas acuáticos próximos (cauce del río, quebradas afluentes al embalse) (Valencia-Rodríguez et al, 2022). En centrales que tienen la descarga de agua turbinada varios kilómetros abajo del pie de presa, entre la base de la presa y el sitio donde retorna el agua al río, es frecuente observar ejemplares de especies de peces de pequeño tamaño como aquellas de los géneros Saccodon, Parodon, Astroblepus y Chaetostoma, los cuales aprovechan los hábitats que ofrece este sector del río .…”

Genetic diversity and structure of Brycon henni in regulated and non-regulated water flow rivers of the Colombian Andes

“…There are currently 25 dam producing over 100 MW of power and an undocumented number of smaller-scale dams (Angarita et al, 2018). Fragmentation due to the inclusion of the wall within the river channel, as well as other effects of dams on the composition of the ichthyofauna in the Magdalena-Cauca basin, have been described, but the impact on local fish populations remains to be systematically explored (Valencia-Rodríguez et al, 2022a;Martínez-Toro et al, 2022). In the Central mountain range, the landscape along the Porce River receives residual water discharge from the six-millionpeople city of Medellín, and its landscape has been highly transformed by agriculture, cattle farming, and urban, suburban, and rural expansion.…”

“…Despite the construction of several hydropower projects across the distribution range of B. henni, population genetic studies before such interventions have only been carried out in the Ituango area (Landínez-García and Marquez, 2020); thus, little evidence is available to contrast the historical and current population structure of B. henni in the dam-regulated water flow areas. In addition, a decrease in the number of captures of B. henni has been reported in the Porce II and III dams from through 2019(Álvarez-Bustamante et al, 1969Valencia-Rodríguez et al, 2022a), and implementation of stocking has been suggested as a measure to reduce environmental damage and guarantee food safety. However, these activities are expensive, complex, inefficient, and their impacts have not been sufficiently documented or monitored by environmental authorities (Mancera-Rodríguez, 2017).…”