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By Mariana Alejandra Moscoso Rodríguez
Javier Alejandro Maldonado Ocampo
Juan David Vargas Alonso
Translated by Donald Taphorn
Photo by Mariana Alejandra Moscoso
DECREASING FISHES of the MAGDALENA-CAUCA RIVER BASIN
Colombia ranks second in the world in freshwater fish species richness, with a total of 1,497 species, of which 371 are endemic. Nevertheless, the aquatic ecosystems in which this great fish species richness is found are experiencing an increase in the intensity of human impacts that negatively affect this special group of vertebrates. More dramatic still is what is happening to the emblematic Magdalena-Cauca River Basin of Colombia, where a total of 219 species of fish have been recorded and where more than half of those are found only in this basin; and where large numbers of families depend on these fishes for their survival.
The River
The hundreds of audiovisual, photographic and written records that exist about the Magdalena River and its main tributary, the Cauca, allude to one of the most important watersheds of the country, and often evoke the exuberant abundance of fauna and flora that accompany its landscapes, interrupted by water courses that flow in a south to north direction for more than 1,500 km. From its source in Magdalena Lagoon in the Páramo de las Papas, in the Colombian Massif, its channel winds along an extensive route that passes through spongy soils of high mountain cloud forests, wetlands, mountain peaks like the Nevado del Tolima and Ruiz, through valleys surrounded by mountain ranges, its waters increasing as tributaries join and accelerate the course of their flows, sometimes slowing in lagoons, marshes, and lowland plains, some of which are even slightly below sea level, before it finally reaches its mouth in Bocas de Ceniza in the Caribbean Sea.
Photos by Cesar David Martínez
This brief description not only brings together our natural history and cultural heritage, it also demonstrates the evolution of ideas that for decades stimulated our use and exploitation of the waters of the Magdalena River, constituting one of the most transcendental processes in the foundation of the socioeconomic, political and cultural development of the country . Every time we inquire about the history and importance of the river in Colombia, it is inevitable not to feel blessed, knowing that its waters were the principal means for development, that fomented the processes of social and cultural integration triggered through various human activities along its shores , such as the traditional fishing practiced by various human groups that for more than fifteen centuries, strengthened our sense of belonging, and maintained consistency in the process of formation and deepening of our national identity that led to great social revolutions and scientific discoveries .
The Problem
The river has been the scene of human progress that allowed the expansion of economic frontiers, as happened during the twentieth century with the emergence of exploration and exploitation of hydrocarbons and the establishment of large hydropower installations, renewable energy sources, but which caused negative environmental impacts affecting its natural fertility of its ecosystems and life cycles of its many and varied aquatic organisms. The well-being of the Magdalena Cauca River Basin should occupy a special place to guarantee its continuity, but that is not the case, the reality is very different, the current state of conservation of the Magdalena-Cauca Basin is seriously degraded, and the 219 species of fishes that inhabit its waters are gravely endangered .
But are these the only causes of the environmental deterioration of the basin? The answer to this question is not easy, because the basin and its fishes have been subject to many and diverse pressures such as the discharges of industrial effluents, sewage and solid waste discharges of untreated water, mining and industrial pollution that releases lead, cyanide and mercury . The processes of extraction of oil and its derivatives also alter water’s dissolved oxygen content, salinity and temperature, essential parameters for the life of the ichthyofauna, as well as extensive deforestation for livestock ranching, illicit crops and other factors that affect an immense area for their development. All these activities, combined with overfishing in the basin, certainly explain why there has been a very rapid decline in fish production in the basin which was around 81,653 metric tons per year in the 1970s compared to only 39,000 metric tons in 2010 .
 Overfish in Magdalena River |  Agricultural fields |
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 Agricultural fields |  Livestock in Páramos ecosystem |
 Rice production |  Hydropower plant |
 Growing sorghum |  Overfish in Magdalena River |
 Navigability Magdalena River |  Agroindustry |
 Livestock |  Cienaga Grande de Santa Marta |
 Zona Industrial Barranquilla. RÃo Magdalena |
Photos by Cesar David Martínez
Theaws and Regulations
In Colombia, since the enactment of the natural resources law (Law Decree 2811 of 1974) and the subsequent issuance of Law 99 of 1993, companies are obligated to identify and characterize the impacts on the environment caused by their activities. Those laws also defined the sanctioning regime to be applied to those who violate existing legal provisions. It was further established that those impacts that cannot be prevented, mitigated or corrected, should be compensated.
In 2012, the Ministry of Environment and Sustainable Development (MADS) issued, through Resolution 1517 of 20128 , a Handbook for the allocation of compensation for loss of biodiversity in terrestrial ecosystems , in order to provide a simple application tool to calculate the area of natural ecosystems affected and to define, through specific calculations, the area of the ecosystems to compensate to avoid the net loss of biodiversity in the areas of influence of the licensed projects. In addition, the Ministry has made progress developing methods to calculate the compensation for aquatic and marine-coastal ecosystems; however, these have not yet been legally adopted.
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However, the level of implementation of the Handbook by users has not been satisfactory, depriving the environmental sector of an important source of economic and technical resources to advance, at a regional and local level, the processes of conservation and restoration of ecosystems. The dynamics of transformation of the natural environment in the country requires a more agile and determined management by the Ministry and the regional environmental authorities to typify and quantify the impacts and also offer alternatives to compensate for inevitable impacts.
The "Handbook for the allocation of compensation for biodiversity loss" establishes the obligation to carry out studies to determine the causes of negative impacts, and where they occur; in the case of hydroelectric projects this means pre-construction and post-construction monitoring of fish and other aquatic biota populations. The proper implementation of environmental licensing processes and the compensation handbook will allow the collection of information and documentation through monitoring and follow-up, how fish communities are affected by the construction of hydroelectric power plants.
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Theaws and Regulations
In this sense, for some years, TNC has been developing a portfolio of aquatic ecosystem conservation for the Magdalena-Cauca River Basin , incorporating fishes since they are very important to determine high priority conservation areas. It is for this reason that this NGO, together with the Ichthyology Laboratory of the Department of Biology of the Pontificia Universidad Javeriana have been working on topics related to research, characterization, monitoring and modeling of various aspects related to the fishes of the Magdalena-Cauca River Basin. As a result of these cooperative efforts, it has been possible to determine that one of the main threats to fish in the basin has been the construction of hydroelectric plants, which interrupt the natural flow regime and the connectivity of river systems, two fundamental elements for the sustainability of fisheries and the continuity of species .
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Our research has combined two essential factors to reach this conclusion; the first result obtained came from an exhaustive and collective literature review and museum specimen verification of available information about the fishes present in the basin, which allowed the creation of a large database on species richness and distribution. Secondly, hydrological river modeling, i.e. an overview of the activity and status of functional stream networks available for fish migration and alteration of the natural flow of river sections downstream of hydroelectric sites, along with wetland areas and the degree of their transformation .
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Photos by Cesar David Martínez and Jorge García
Magdalena-Cauca Basin: Locations with records of fish; Functional subnetworks; Degree of flow control
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Combining data on where and how species are distributed along the river allows the creation of credible models of species distribution, with which questions can be formulated analyzed and, such as where the greatest concentration of migratory species is or which part of the basin are they found? With these distribution models, maps are made that illustrate recurring patterns of fish behavior in the basin. Once the data and maps have been prepared, it is possible to establish how the migratory routes of the species and areas of importance for the development of their life cycles (floodplains) are affected by where the hydroelectric plants are located in the basin .
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Magdalena-Cauca Basin: Models of species distribution; Wealth of migratory species through distribution models (Maps developed by Guido Herrera)
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The results obtained so far indicate that the river network connected to the floodplain systems is now 8,311 km long, which, when compared to the natural condition present before the construction of hydroelectric plants (11,998 km), indicates a loss of 30.4% of the length of rivers connected to these systems. In fact, only 3.3% of the total length of the river is affected by fragmentation between 0 - 400 meters above sea level (masl), but between 400 and 1,000 masl elevation this figure reaches 56.3%, and higher up, between 1,000 - 1,500 masl, 81% . This has important implications for fish species in the basin, such as migrating for reproductive and / or feeding purposes, since the loss of habitat for migratory species follows the same pattern of loss of connectivity already described. That is to say 4% loss between 0 - 400 masl, 35.3% between 400 and 1,000 msnm and 76.4% between 1,000 - 1,500 masl. This whole panorama of current and future fragmentation by the hydro-energetic development in the basin also increases the risk of extinction of the fish species distributed in it, since their ranges of distribution are reduced and the vulnerability due to loss of suitable habitat conditions required for their survival increases. .
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Magdalena-Cauca Basin: Risk of extinction of fish for present and future hydroenergetic development (Maps developed by Guido Herrera)
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We can make an analogy between the situation of the Magdalena-Cauca River Basin and our own circulatory system. What would happen to our health if our blood circulation were plugged in several different places? We would collapse and this would lead to death. The same thing is happening to our great river, with all these artificial blockages because of the hydroelectric dams that cut off the natural flow of the river. If river water flow is dammed and is subject only to the demands of energy generation to determine how much and when water is released to flow downstream, as a consequence the natural hydrological pulse of the wet and dry season in uncontrolled rivers is completely lost, and as a direct result the natural triggers for fish migrations for reproductive and nutritional purposes disappear, and fishes are completely disoriented.
To cite an example let’s assume that the dry season is starting today but from time to time the dam’s floodgate is opened to release water and dammed sediments, these releases change the dynamics of connection between the floodplain systems such as marshes and the main channel of the river. Swamps are the ecosystems where migratory fish species grow, juveniles are fed and take refuge in dense aquatic vegetation, that is to say where they fulfill a critical phase of their life cycle, but if the flow between the marsh and the river is altered because the amount of water discharged from a dam is regulated and does not correspond to natural annual cycle this has a very large negative impact on the dynamics of floodplain. And so, the reproduction of the species is also affected, as in the case of the Ciénaga Grande de Santa Marta, where one of the worst ecological disasters of the country was committed, when all water connections between the swamp and the sea were obstructed.
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Sketch of the Future
The final chapter of the history of the Magdalena River has not yet been written, its waters inspire disturbing projects that would guarantee the end of all life that depend upon its waters and would displace cultural and environmental structures that have been generated through the flow of time. Projects such as the Master Plan, prepared by Hidrochina which aims to create 17 new hydroelectric plants (which could be ready by 2030), challenges our determination in Colombia for the conservation of our natural resources. It is as if the private interests of energy producers outweigh the welfare of the species of aquatic life, their habitats and the human communities that depend on these resources.
Colombia has a total of 1,495 species of freshwater fishes, of which 220 are found in the Magdalena-Cauca River Basin. This diversity richness and high endemism has sustained the main national freshwater fishery throughout history, based on at least 40 species, of which 16 are known to carry out reproductive migrations from the lowland floodplains to the rivers in the foothills of the Andes (for example the Bocachico and the Striped Catfish, both emblematic species of the basin). It can be said that the cultural and economic importance of these species for fishermen who for decades have benefited from fish as an animal protein and economic resource is nowadays almost a legend. The decline of fish is so severe that their former abundance and wealth can only be found in the hundreds of audiovisual, photographic and written records of what our river basin once was.
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Bagre Rayado (Pseudoplatystoma magdaleniatum)
Viscaina (Cyphocharax magdalenae)
Doncella (Ageneiosus pardalis)
Bagre Rayado (Pseudoplatystoma magdaleniatum)
Migratory Species of Magdalena-Cauca Basin
Photos byy Jorge García
Notes
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1. Torres León, F. 1967. La comunidad de pescadores de Honda. Centro de Estudios Sociales.
2. Ideam-Cormagdalena. 2001. Estudio ambiental de la Cuenca Magdalena-Cauca y elementos para su ordenamiento territorial.
3. Miles, C. 1971. Los Peces del río Magdalena. Universidad del Tolima.
4. Castaño-Uribe, C. 2003. Río Grande de la Magdalena. Banco de Occidente.
5. Mojica, J.I., Usma, J.S., Álvarez-León, R. y Lasso, C.A. (eds). 2012. Libro rojo de peces dulceacuícolas de Colombia 2012. Instituto de Investigación de Recursos Biológicos Alexander von Humboldt, Instituto de Ciencias Naturales de la Universidad Nacional de Colombia, WWF Colombia y Universidad de Manizales. Bogotá, Colombia.
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6. Galvis, G. y J. I. Mojica. 2007. The Magdalena River freshwater fishes and fisheries. Aquatic ecosystem health and management 10: 127-139.
7. The Nature Conservancy, Fundación Alma, Fundación Humedales y AUNAP. 2016. Estado de las planicies inundables y el recurso pesquero en la macrocuenca Magdalena-Cauca y propuesta para su manejo integrado. Bogotá, Colombia.
8. Ministerio de Ambiente y Desarrollo Sostenible (MADS). 2012. Resolución 1517 “Por la cual se adopta el Manual para la Asignación de Compensaciones por pérdida de Biodiversidad”.
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9. Ministerio de Ambiente y Desarrollo Sostenible (MADS). 2012. Manual para la asignación de compensaciones por pérdida de biodiversidad. Ministerio de Ambiente y Desarrollo Sostenible.
10. Tellez, P., Petry, P., Walschburguer, T., Higgins, J. y Apse, C. 2012. Portafolio de conservación de agua dulce para la Cuenca del Magdalena-Cauca. Cormagdalena, Fundación Mario Santo Domingo, he Nature Conservancy, Colombia.
11.Carvajal-Quintero, J.D., Januchowski-Hartleyb, S.R., Maldonado-Ocampo, J.A., Jézéquele, C., Delgado, J. y Tedesco, P.A. (2017). Damming fragments species ranges and heightens extinction risk. Conservation Letters. Available online 10 December 2016.
12. Angarita, H., Wickel, A.J., Sieber, J., Chavarro. J., Maldonado-Ocampo, J.A., Herrera-R, G.A., Delgado, J. & Purkey, D. (2017). Large scale impacts of hydropower development on the Mompos wetlands, Colombia. (En preparación).
13. DoNascimiento, C., Herrera, E.E., Herrera, G., Ortega-Lara, A., Villa-Navarro, F., Usma, J.S. & Maldonado-Ocampo, J.A. Checklist of the freshwater fishes of Colombia: a Darwin Core alternative to the updating problem. Zookeys (En prensa). ​
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Photo by Cesar David Martínez