Spawning Grounds Model For Neotropical Potamodromous Fishes: Conservation And Management Implications

Silvia López-Casas ^1* Carlos Rogeliz ^2* Victor Atencio-García ^3,4 Cintia Moreno-Árias ^5,6 Diana Arenas ⁷ Kelly Rivera-Coley ^5,6 Luz F Jiménez-Segura ^5,6

• ¹ Wildlife Conservation Society, Bogotá DC, Colombia
• ² The Nature Conservancy, Bogotá DC, Colombia
• ³ Centro de Investigación Piscícola de la Universidad de Córdoba - CINPIC, Montería, Colombia
• ⁴ University of Córdoba, Montería, Córdoba, Colombia
• ⁵ Grupo de Ictiología de la Universidad de Antioquia - GIUA, Medellín, Colombia
• ⁶ University of Antioquia, Medellín, Antioquia, Colombia
• ⁷ Integral S.A., Medellín, Colombia

Freshwater fish migrations are an important natural process. All South American main river basins have potamodromous fish that migrate upstream to spawn. These species withstand fisheries, therefore are socially, economically, and ecologically important. Hydropower is the most important source of low-carbon energy in South America, where, in turn, the most diverse and endemic riverine fish fauna inhabits. Nevertheless, hydropower development does not consider spawning areas nor cumulative impacts in fish migratory routes at a macro-basin scale in their Environmental Impact Assessments. To show the potential use of early planning tools at macro-basin scale to ensure that freshwater ecosystems remain functional in supporting fish migrations, a distribution model of potential spawning areas of migratory fish species was built, using the Magdalena basin in Colombia as a case study.Methods: Potential spawning areas for 15 migratory fish species were estimated using ichthyoplankton sampling records, embryonic and larval time development, water velocity and average flow times estimations. Spawning distribution grounds, analyzed for species diversity and richness, were overlaid with the national hydropower projects portfolio to estimate the potential loss of reproduction areas due to hydropower dam development.Our basin-wide model calculated spawning areas for all of the species identified in the ichthyoplankton samples, using available data on larval and embryonic development times. Our model estimated the potential impacts of projected hydropower development in the basin and revealed spawning grounds encompassing 11,370 km of rivers, spanning Strahler orders three to eight, which represented 11.2% of the entire river network. These areas overlapped with 80 hydropower projects (56.7% of the total), with a projected 45.0% loss in reproduction areas for potamodromous species.Conclusions: Management measures to promote freshwater fish species conservation must avoid river fragmentation and critical habitat loss, whilst promoting habitat connectivity. Our model provides a solution for data-limited basins to analyze fragmentation impacts from hydropower dam development. It supports science-based decision-making for choosing dams configurations that minimize impacts (connectivity and reproductive habitat loss), whilst ensuring that rivers continue to support migratory fish for better conservation and food security outcomes.