Freshwater migratory fish populations are experiencing a dramatic global decline. A new international scientific assessment highlights a significant drop recorded over recent decades and stresses the urgent need for coordinated action among countries. This issue affects hundreds of species and threatens ecosystems, economic activities, and human communities relying on river systems.
The new global report and available data
The new “Global Assessment of Migratory Freshwater Fishes,” presented at CMS COP15 in Brazil, highlights that many of the world’s major wildlife migrations occur underwater. The report, based on extensive global datasets and IUCN assessments, analyzes nearly 15,000 freshwater fish species, providing the most comprehensive overview currently available of their conservation needs.
An unprecedented population decline
According to the study, freshwater migratory fish populations have declined by about 81% since 1970. In addition, almost all species included in the CMS are threatened with extinction. The situation is further complicated by the existence of more than 250 transboundary water bodies, covering about 47% of the Earth’s surface.
The importance of international cooperation
The assessment emphasizes that protecting these species requires managing rivers as interconnected systems rather than isolated national waterways. By aligning science, policy, and international cooperation, governments can help safeguard migrations and the ecosystems connected to them.
The main causes of the crisis
The decline of these species is linked to several factors:
- Dam construction
- Habitat fragmentation
- Pollution
- Overfishing
- Climate change
These pressures are accelerating the decline of species whose life cycles depend on interconnected rivers.
At-risk species and priority areas
The analysis identifies 325 species requiring urgent international conservation action. Their distribution includes:
- Asia: 205 species
- South America: 55
- Africa: 42
- Europe: 50
- North America: 32
Priority river basins include the Amazon, Río de la Plata-Paraná, Danube, Mekong, Nile, and Ganges-Brahmaputra.
Proposed tools and solutions
The report outlines several immediate actions:
- Protection of migratory corridors
- Safeguarding environmental flows
- Basin-scale management plans
- Transboundary monitoring
- Coordinated seasonal fishing
These measures aim to ensure ecological continuity within river systems.
The Amazon case and Brazil’s initiatives
Brazil has proposed specific conservation measures for the Amazon and Río de la Plata-Paraná basins, considered crucial for biodiversity. A case study identifies 20 migratory fish species that could be included in CMS Appendix II.
Among them is the golden catfish (Brachyplatystoma rousseauxii), known for migrations up to 11,000 km and for supporting regional fisheries valued at approximately 436 million dollars per year.
A multispecies action plan (2026–2036) has also been proposed, along with the inclusion of the spotted catfish (Pseudoplatystoma corruscans) in Appendix II, highlighting the need for coordinated action in the Río de la Plata basin.
The role of global cooperation
According to CMS, these initiatives represent some of the most ambitious international efforts undertaken so far to protect freshwater migratory fish species. Their success depends on applying conservation solutions across the entire distribution range of species and on effective international cooperation.
Managing rivers as shared systems is considered essential to prevent the permanent loss of these migrations.