From the murky waters of the Amazon River, a fisherman pulls out a striking creature. Its sleek, over a meter-long body with silver skin and whiskers shimmers in the bright tropical sun.
Dorado catfish, also known as gilded catfish (Brachyplatystoma rousseauxii), are a large freshwater migratory species.Each year, these giants travel thousands of kilometres through the vast arteries of the Amazon Basin, undertaking the longest migration of any freshwater fish on Earth.
Its only recently, in 2017, that scientists uncovered the true scale of this journey. Over their 12- to 15-year lifespan, the catfish travel between 8,000 and 12,000 kilometres a distance nearly equal to the entire length of South America. But this remarkable discovery was coupled with growing concern: human-caused disruptions along the migratory route could one day stop the fish from making the journey altogether.
From 23 to 29 March, governments, experts, and civil society representatives from around the world are gathering in Campo Grande, Brazil, for the 15th meeting of parties to the Convention on the Conservation of Migratory Species of Wild Animals (CMS COP15), the preeminent treaty focused on the conservation of migratory species and their habitats.
With Brazil, home to the Amazon Basin, hosting the COP, momentum is building to protect the dorado and all migratory freshwater fish. A new report launched by the CMS, the Global Assessment of Migratory Freshwater Fishes, aims to put these species at the top of the agenda and support their survival by highlighting their role in the environment and in economies and the need for countries along migration routes to strengthen conservation.
Life cycle written in motion
The dorados journey begins near the foothills of the Andes, where mountain rivers plunge into the Amazon Basin. Carried downstream by powerful currents, the larvae drift with the flow and travel thousands of kilometres across the vast Amazon floodplains.
When the dorado arrive at the estuary, where the Amazon River meets the Atlantic Ocean, the fish have developed into juveniles. In this area, fresh river water combines with salty ocean water, forming one of the most nutrient-rich ecosystems on Earth. For two to three years, the catfish feed and grow in this abundant environment, building the strength they will need for the next stage of life.
When the fish reach adulthood, they begin the journey back home. Triggered by seasonal rains in the western Amazon, rising water levels indicate that it's time to migrate. As the rivers swell, new pathways emerge across the basin, and once-narrow streams transform into vast aquatic highways. This allows the adult catfish to swim upstream against the current back toward the Andes. Upon reaching the headwaters, the catfish spawn, marking the beginning of a new life cycle.
The lifelong journey illustrates how the Amazon operates as a single, interconnected ecosystem stretching from the Andes to the Atlantic Ocean and how the survival of its many migratory species relies on the entire route being conducive for their travels.
Predator and prey
Its not only the dorados incredible journey that makes it so important. It also plays key roles in the Amazon river system. As an apex predator, it helps structure the aquatic food systems and maintain ecological balance. Declines in such important predators can trigger a cascade of destabilizing effects on the health and balance of the entire ecosystem.
The dorado along with other Amazonian catfish are also a key component of human food security throughout the region, providing a key source of protein for millions and livelihoods. The migrations of these catfish underpin some of the most important commercial fisheries in the Amazon, fuelling local economies.
Disruptions on the way
The species migration, however, is becoming more difficult. The CMSs new Global Assessment report highlights how new dams and hydropower infrastructure across the Amazon are reshaping ecosystems for freshwater fish. These projects disrupt the natural flow of rivers, affect water temperatures, and decrease seasonal flooding that nourishes floodplains. More importantly, poorly designed infrastructure can obstruct essential migration routes, preventing fish from accessing the spawning grounds crucial to their life cycles.
Meanwhile, the report also notes that despite its economic benefits, the Amazons fishing industry is ripe with unsustainable practices and high fishing mortality rates, preventing populations from replenishing themselves. Waterborne pollution, deforestation and climate change are further destabilizing already fragile systems and threatening the species.
These challenges are not unique to the dorado and other freshwater fish in the Amazon. Infrastructure, species exploitation, pollution, habitat degradation and fluctuations in natural rhythms are disrupting the migrations of species around the world moving not only through water but also across land and air.
The Amazonian catfish are incredibly unique creatures, but theyre also emblems of the challenges facing migratory species across the world, said Amy Fraenkel, the Executive Secretary of the CMS. If we disrupt their migratory patterns and habitats, we will also disrupt our own economies and well-being.
A case for increased cooperation
Migratory fish do not recognize national borders, and no single country can effectively address the growing threats to Amazonian catfish and other migratory species. This is why the CMS is pushing for increasing collaboration among countries to secure safe migration routes holistically rather than through a part-and-parcel approach. On the table at the upcoming CMS COP15 is the Multi-species Action Plan for Amazonian Migratory Catfish, which would improve the conservation and sustainable use of these species and their priority habitats.
The CMS collaborates with governments to promote regional coordination for mapping and protecting migration routes, restoring connectivity and environmental flows, regulating fishing, and reducing pollution. It also advocates for the involvement of Indigenous peoples and local communities in decision-making.
With scientific knowledge now at hand, we hope that at the upcoming COP, Parties will translate evidence into ambition and ambition into coordinated action that keeps migratory species moving and freshwater ecosystems thriving, said Fraenkel.
