A study coordinated by Embrapa Pesca e Aquicultura (TO) successfully more than doubled the weight gain of tambaqui, also known as cachama or gamitana (Colossoma macropomum), in net cages.
By employing hormonal and dietary supplementation techniques, scientists achieved an average weight of 1.7 kg in ten months under this production system. This represents a weight gain rate 2.04 times higher than the typical result, which is approximately 1 kg in twelve months. These findings correspond to tanks with a density of 40 kg per cubic meter (kg/m³), with weight gain calculated based on the monthly average.
Enhancing tambaqui production in net cages is one of the priorities of agricultural research focused on fisheries and aquaculture, as it can contribute to the socio-productive inclusion of small-scale fish farmers. This is the case with the project “Uso de populações monossexo de tambaquis”, or Monotamba, led by researcher Flávia Tavares, which yielded these results.
Cachama Farming
Producing cachama in net cages is an efficient and environmentally responsible way to cultivate this species, promoting sustainable aquaculture with increasing productivity gains. Additionally, it facilitates access to local markets in riparian regions, enabling production closer to final consumers, which can reduce transportation costs and improve the quality of the final product.
The research exclusively used female tambaqui, as they demonstrate higher weight gain. The fish were administered estradiol hormone during the rearing phase for six weeks. Part of the study was conducted in a Recirculating Aquaculture System (RAS), while another part took place in a net cage in Lago de Palmas, where Embrapa has been conducting experiments in this production system.
Another related initiative, under the BRS Aqua project, had previously reduced the time for tambaqui to reach 1 kg from twelve to nine months in a net cage at a density of 40 kg/m³. This was achieved through management strategies such as fish grading and adjustments to feeding schedules.
The Monotamba project also yielded positive results with a mixed population (where males and females were raised together). The weight gain reached 1.4 kg in ten months, which is considered a favorable outcome. This population did not receive estradiol during the rearing phase and served as a control group in the net cage, meaning it was the baseline comparison for the hormone-treated group, which consisted exclusively of females.
Feed Conditioning
During the rearing phase in the indoor system, the fish were fed exclusively with pellets, conditioning them to this type of feed. When transferred to the net cages in Lago de Palmas for grow-out, they were already accustomed to this feeding method. According to the researcher, “they behaved like tilapia when feeding, something not observed before.” In this context, tambaqui reached 1 kg in about six and a half months—very close to the performance of tilapia, which typically reaches that weight in six months.
Tavares highlights that the significant and rapid weight gain was largely due to the nutritional training the females underwent during the rearing phase. This demonstrates the strong connection between different stages of aquaculture production, where early-stage practices can have positive or negative effects on later phases. In this case, the impact was beneficial.
She also emphasizes that indoor feed training “conditioned the fish to start feeding on pellets earlier, making them much more eager for food than untrained fish, which made a significant difference.” This difference contributed to the observed weight gain and opens up promising prospects for tambaqui production in net cages.
Science and Industry Collaborate to Develop Technological Packages for Tambaqui
This improvement in weight gain is part of a larger process built through collaboration between research and the aquaculture industry to enhance tambaqui productivity in net cages, according to the researcher. Unlike tilapia, which already has established production protocols and technological packages, tambaqui lacks a complete production framework. This is a key reason why tilapia remains the most farmed and exported fish species in Brazil.
The results from Monotamba are primarily zootechnical, meaning they focus on husbandry and production. However, economic analyses, which are just as crucial, are still lacking. According to the researcher, “it is necessary to calculate economic indicators to determine whether the cost of keeping fish in indoor systems for extended periods will be financially viable for producers.”
A fundamental consideration is that since the fish are conditioned from the start to consume only pellet feed—and this feed can account for up to 80% of production costs—understanding the right quantity and timing of feeding becomes even more critical for fish farmers.
Beyond the current weight gain improvements, increasing stocking densities in net cages is another future advancement. Tavares believes a density of 50 kg/m³ is feasible. This would further narrow the production gap between tambaqui and tilapia, which is typically farmed at higher densities.
The researcher contextualizes the current stage of the work: “We are making progress; this is part of a broader process. We will have improved tambaqui strains for net cages, and genomic editing will also contribute to weight gain in this production system. Tambaqui has enormous potential, especially for Brazil’s northern region.”
Contact
Flávia Tavares de Matos
Embrapa Pesca e Aquicultura
Email: flavia.tavares@embrapa.br
