In this Spanish-language article, Mongabay describes the decline of catfish and other migratory fish in rivers around the world. “Hydroelectric plants and other infrastructure works, overfishing and pollution are the main causes.”
“After more than two decades researching the Amazon, Carolina da Costa Doria, postdoctoral fellow in fisheries management at the University of Florida (United States), explains that dams disrupt the connectivity of rivers and alter the movement, feeding and reproduction of fish. fish , especially those that survive only in long stretches of fresh water, such as large migrants.
"These predators are essential to maintain the ecological balance, food and income of Amazonian families. It is necessary to maintain large free sections in the rivers and to follow the adaptation of the species to the works already implemented. The new dams will have very serious repercussions for the economies and the people who depend on these species, ”says da Costa Doria, who is now a professor at the Federal University of Rondonia.”
“Migratory fish populations have declined by 76% in various regions of the planet since the 1970s. Losses were greatest in Europe (93%) and in Latin America and the Caribbean (84%). The rates are higher than those of terrestrial and marine species.”
““Fish are important from a cultural point of view, especially for indigenous peoples; from the social, for recreation and mental health; from the economic, for fishing and other commercial activities; from the nutritional, as the world's largest source of protein; and from the ecological, to maintain biodiversity and the balance of ecosystems. There are very good reasons to protect fish for future generations ”, explains Professor Lee Baumgartner, post-doctorate in Ecology from the University of Canberra (Australia).”
“The Amazon has more than 50 migratory species , including the largest freshwater marathoner. El Dorado travels 8000 kilometers between the Andean regions and the mouth of the Amazon River. But, the great champion also suffers from human actions. The largest dorado ever recorded was almost 2 meters. Today, they are half the size.”
“In the Madeira river complex, there are plans to build the binational plant of Ribeirão, in Nova Mamoré (RO), and of Cachuela Esperanza, on the Beni river, in Bolivia. The measures adopted for the passage of fish in these structures are under permanent observation and criticism of the experts.”
“Deforestation, which amplifies the climate crisis, also complicates the multiplication of species. Changes in temperature can trigger fish migration and reproduction. This causes such events to happen at inappropriate times, for example, at times of the year when the waters are low or there is not enough food in the rivers for adults and young.”
“Fish passages are often approved without testing whether they will benefit migratory species. Studies show that these measures can be an ecological trap, even more so without qualified tools to select the best systems for certain rivers ”, says Luiz Gustavo Silva, from the Federal Institute of Technology in Zurich (Switzerland).”
According to Luiz Gustavo Silva, from the Federal Institute of Technology in Zurich (Switzerland), “Rivers without free reaches are lethal for migratory fish. Like jaguars, they are indispensable for the conservation of large spaces and many other species. There will be no truly sustainable dams with projects that continue to weigh more than all economic variables. We need to attack this scenario with more science and public debates on power generation and environmental conservation ”
Additional photos, maps, diagrams, and video can be found at the original article.