Drivers for the artisanal fisheries production in the Magdalena River

Abstract

We review knowledge on the Magdalena River in Colombia and its fish to identify those drivers that influence the artisanal fisheries production. We identify eight direct drivers (four natural and four anthropogenic) and at least four indirect drivers. Those drivers modify conditions in the fluvial network that promote fish movements, reproduction, and their larvae survivor. Landscape, rains, floods, connectivity of the fluvial net as land cover change, water pollution, hydropower, and alien species are the natural and anthropogenic direct drivers described in this article. The river–lake interaction dynamics in the Magdalena River are determined by two rainy cycles per year. Two seasonal flooding periods induce two cycles in the biological productivity of floodplains because water and sediment inputs. The most visible consequences in these hydrological cycles are the migrations of potamodromous fish and the periodic increase in the artisanal fishery production. Major floodplains are reducing their storage capacity by trapping ∼10%–40% of upstream sediment production. This process induces many research questions about rates of biomass production, carbon fluxes in the basin, impacts of human-induced erosion, and increasing rates of sediment load on floodplain connectivity, but still there is not enough data to answer them. Finally, we make some suggestions toward the sustainability of the Magdalena floodplains. The well-being of the floodplain ecosystems and their connectivity with the main river are the main tools to preserve and manage the ecosystem services of the Magdalena River and its floodplains lakes.

Causes and consequences of recent degradation of the Magdalena River basin, Colombia

“…Similarly, in the delta region of the CGSM, the ENSO‐driven periods of flood and drought influence the freshwater input from the Magdalena River into the CGSM wetland complex resulting in hypersaline conditions during dry events (Jaramillo et al 2018 b ). Together these results suggest that during El Niño years, floodplain lakes with a higher degree of connectivity to the Magdalena River could face major droughts and substantial reductions in river flow, leaving them hydrologically isolated (Jimenez‐Segura et al 2022).…”

“…Basin‐scale analyses on the lower river floodplains (Mojana; Fig. 1) further show that new hydropower infrastructure could drastically enhance (> 90%) habitat fragmentation between lowland floodplains and upstream fish spawning habitats (Angarita et al 2018; Jimenez‐Segura et al 2022). It could also intercept > 80% sediment load through the new dams (Angarita et al 2018).…”

“…El Niño–Southern Oscillation (ENSO) influences the hydro‐climatological conditions of the Magdalena River basin, with extended periods of low precipitation (droughts) during El Niño events and prolonged rains (floods) during La Niña events (Restrepo and Kjerfve 2000). These climatological conditions are essential in connecting the main river and adjacent wetland and lake systems (Blanco et al 2006; Jimenez‐Segura et al 2022) (Fig. 4).…”

“…Hydropower infrastructure accounts for almost half of Colombia's electric demand in the Magdalena River basin, with an expected three‐fold increase in the coming decades (Angarita et al 2018). Appraisals of the impacts of these dams on the aquatic communities show that cumulative hydrologic alterations, coupled with the loss of longitudinal connectivity, will destabilize ecosystems by altering species composition and distribution, affecting the natural bimodal migration patterns, and reducing the extent of spawning habitats (Jimenez‐Segura et al 2022). Most fish endemism occurs across the tributary river headwaters; the longitudinal connectivity loss will pose a greater extinction risk for endemic species (Carvajal‐Quintero et al 2017).…”