How Mamirauá fishers helped restore arapaima through canoe-based counts

The arapaima, Arapaima gigas, known as the “cod of the Amazon,” is at the center of one of the planet’s most successful cases of species recovery through community management. The foundation of that success is a precise and remarkably direct practice: local fishers visually count the animals when they rise to the surface to breathe.

Because arapaima have an obligatory form of aerial respiration, they surface every 15 to 20 minutes. That pattern allows local specialists trained by the Mamirauá Institute to estimate population size with 95% accuracy. A species that had been close to extinction became an abundant resource, supporting food security while helping protect entire lakes from destructive fishing.

The Mamirauá Model puts communities in charge

The foundation of this positive impact is the so-called Mamirauá Model, a social technology that transfers the leading role in resource monitoring and use to riverine communities. Rather than relying on outside enforcement alone, the system allows residents to establish rules for the lakes where they live and work.

Those rules include preservation zones, where fishing is prohibited, and management zones, where catches are strictly controlled. This social organization is documented as a powerful conservation tool because it creates a sense of ownership and responsibility among the people who know the territory most closely.

The result is an organic monitoring system. Community surveillance discourages intruders and helps ensure that only the ecosystem’s biological surplus is removed. The reproductive structure of the populations remains intact, while the resource continues to support the needs of riverine families.

The model also changes the relationship between conservation and authority. Rules are not seen only as restrictions imposed from outside, but as agreements to protect a shared resource. In lakes where management is organized, the fishers’ daily knowledge is combined with scientific procedures to guide decisions.

A large fish adapted to low-oxygen waters

Arapaima are among the largest freshwater fish in the world. They can reach three meters in length and weigh more than 200 kilograms, or about 9.8 feet and 441 pounds. Their size helps explain their value, but their biology also shows why community management depends so heavily on careful observation.

The fish has a modified swim bladder that works in a way similar to a lung. This evolutionary adaptation allows it to extract oxygen from atmospheric air and is crucial for life in slow-moving, oxygen-poor environments such as floodplain lakes.

The same adaptation that helps arapaima survive also makes them visible and vulnerable. They must rise to the surface and can therefore be hunted with harpoons. That vulnerability explains the vital importance of community protection zones, where capture is prohibited or subject to strict rules.

The species also displays important parental behavior. Arapaima care for their young, and males protect the fry during the first weeks of life. That behavior helps make management effective: when communities protect breeding sites during the closed season, they secure very high recruitment rates.

Established biological science shows that areas under community management can see arapaima populations increase by as much as 400% in just one decade. The figure challenges any catastrophic view of natural-resource use in the Amazon when extraction is carried out with scientific rigor.

Counting sets the harvest limit

Counting is the scientific heart of the management system. It is conducted annually and determines the fishing quota for the following year. In general, that quota does not exceed 30% of the adult individuals counted in the previous year, a limit that prevents overfishing.

During the count, fishers position themselves quietly in canoes and watch for the “boio,” the moment when a fish rises to breathe. Each surface trace, together with the sound of a tail slap, gives an experienced observer a clue about the animal’s approximate size.

The estimate requires attention, memory and knowledge of fish behavior. Local specialists trained by the Mamirauá Institute turn those observations into information for managing the population. The 95% accuracy associated with the work shows that riverine knowledge can produce consistent data for conservation decisions.

This combination of a fisher’s trained eye with academic statistical formulas defines a modern approach to environmental management in Brazil. The system is internationally recognized as an example of a circular bioeconomy because it links species protection, controlled use and community well-being.

Income, food security and riverine empowerment

The economy generated by sustainable management acts as a force for social transformation deep in the forest. Managed arapaima command a high market value because of their traceability and superior quality, since slaughter follows strict sanitary standards.

Sales profits are distributed equitably among community members. The money finances everything from solar-power generators to educational infrastructure. According to data from the Mamirauá Institute, management not only generates income, but also reduces territorial conflicts by establishing clear rules for shared use.

The benefit is not limited to the fish that reach the market. By increasing arapaima availability and organizing harvests, the model also reinforces food security. Community members help define the rules, monitor the condition of the lakes and determine how much can be removed without threatening the continuity of the population.

In this sense, biodiversity conservation becomes an economic strategy for development in Brazil’s North. Protection is no longer an isolated obstacle to local activities. It becomes the condition that preserves the resource’s value and supports the stability of the territory.

Protecting arapaima protects the whole lake

Protecting lakes for arapaima management benefits hundreds of other species. When a community guards a lake against illegal arapaima fishers, it automatically protects turtles, caimans and many smaller fish species that live there as well.

This umbrella effect is essential to the integrity of ecosystem services. Conservation does not focus only on a large fish, but maintains the conditions of an entire environment, including its associated species and ecological relationships.

Maintaining water quality and the vegetation of aquatic macrophytes around the lakes supports carbon sequestration and local thermal balance. Arapaima therefore becomes an ambassador for a healthy biome, where human presence stops being a threat and becomes a force sustaining wildlife.

The success of arapaima management in Mamirauá shows that the future of the Amazon does not depend only on prohibition. It also depends on the qualified inclusion of people who know the rivers, lakes and every signal given by the fish. When riverine residents are treated as forest scientists and arapaima as a renewable heritage, a cycle of prosperity can cross generations.

The most advanced technology for saving the planet may be found at the end of an oar, guided by the wisdom of people who know every breath rising from the silent waters of the Amazon. In Mamirauá, observation becomes data, data become rules, and rules sustain both biodiversity and community life.

Reporting: Anne Silva / Amazonia Mag