One of the strategies used to improve fish production is lowering the feed costs and the environmental impact by reducing dietary protein content. Using the deletion method, we determined the optimal amino acid (AA) ratio for Nile tilapia (Oreochromis niloticus) (body weight 20 g). Eleven experimental diets and four replications, taken two at a time, distributed in a randomized block design were used. For this trial, a balanced diet (BD) was formulated. Ten other diets were formulated by the deletion method, in which the BD diet was adjusted to result in a reduction of 45% of the test amino acid. Fish were fed three times a day for 57 days. Groups of fish at the beginning and at the end of the experiment were euthanized for further determination of the carcass nitrogen (N) composition. The optimal ratio of each AA was derived by dividing the requirement for each AA by the requirements for lysine. The essential AA ratios, expressed relative to lysine (=100), were methionine 64, threonine 93, tryptophan 24, arginine 125, histidine 34, isoleucine 57, leucine 96, valine 76 and phenylalanine 101. Our findings might be used to design strategies aimed at reducing the production costs of Oreochromis niloticus.

Freshwater pond aquaculture is the prevailing fish culture system worldwide, especially in developing countries. The sustainability of such systems has not been assessed and it can be improved based on suitable scientific analyses. In the present study, we apply the emergy synthesis to assess the sustainability of lambari aquaculture, used as a model of freshwater pond monoculture in Brazil, to identify the key practices, and to propose changes to improve them towards sustainability. As a study model, nine semi-intensive lambari farms operating at three levels of management were evaluated: low (LC), moderate (MC) and high (HC) control. Results showed that the main inputs for LC were services (27–46%), feed (7–39%) and water (15–21%), while for the MC and HC farms, they were feed (35–49% and 17–48%, respectively) and services (33–39% and 26–36%, respectively). All farms required more than 60% of their emergy from purchased inputs, resulting in low emergy sustainability index (ESI = 0.1–0.5). Increasing juvenile productivity, using superficial water instead of springwater, controlling pond fertilization and replacing animal protein in diet composition by vegetable sources can lead systems to higher efficiency and resilience, increasing sustainability.

Protected areas have been used worldwide to conserve natural resources. Nevertheless, economic activities to provide income for communities living within and surrounded by conservation areas remain an issue. This study aimed to assess the sustainability of a Deuterodon iguape hatchery, situated within an Atlantic Rainforest Park, to leverage grow-out farming of this small native fish, affording income and food security for local families. We have used a set of indicators of economic, social, and environmental sustainability. The initial investment is about US$ 40,000, which should see a return in ~2 years. The internal rate of return is close to 50%, including the externality costs, which is attractive for both public and private investors. The hatchery generated few direct jobs, but the workforce can be recruited from the community, and the hatchery can enable the establishment of several small grow-out farms, leveraging the development of indirect jobs and self-employment. The system had a low environmental impact, showing a minor release of pollutants, a low risk for biodiversity, and absorption of 18 g of CO2 equivalent per thousand post-larvae produced, contributing to the struggle against climate change. Therefore, the D. iguape hatchery demonstrates the potential of combining biodiversity conservation and income generation, meeting the Sustainable Development Goals of Agenda 2030.

Freshwater pond aquaculture is the prevailing fish culture system worldwide, especially in developing countries. Climate change outcomes and inadequate environmental practices challenge its sustainability. This study applies emergy synthesis to assess the environmental performance of freshwater pond aquaculture in Brazil, aiming to identify and propose practices towards sustainability. As a study model, nine semi-intensive lambari farms operating at three levels of management were evaluated: low (LC), moderate (MC) and high (HC) control. Results showed that the main inputs for LC were services (27-46%), feed (7-39%), and water (15-21%), while for the MC and HC farms, they were feed (35-49% and 17-48%, respectively) and services (33-39% and 26-36%, respectively). All farms required more than 60% of their emergy from purchased inputs, resulting in low emergy sustainability index (ESI = 0.1-0.5). Replacing animal protein and oil on diet composition by vegetal sources, using superficial water instead of springwater, increasing juvenile productivity, and controlling pond fertilization can lead all systems to higher efficiency and resilience, increasing sustainability.