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a b s t r a c tThe accelerated and disorderly expansion of aquaculture can lead to economic, social, and environmental problems. In this sense, it is necessary to prioritize the adoption of practices that aim for sustainable production. The aims of the present study were to identify the contributions from nature and economy in the system of tilapia cage farming. In addition, emergy accounting was utilized to evaluate whether the use of periphyton as a complementary food and the reduction of storage density improve the sustainability of this production system. Three different production managements were evaluated and compared: using traditional stocking density adopted by farmers (80 kg/m 3 ) with 100% of the daily recommended feed and without substrates for periphyton (TRAD); traditional stocking density (80 kg/ m 3 ) with 50% of the daily recommended feed and with substrates for periphyton (TDS); lower density (40 kg/m 3 ) with 50% of the daily recommended feed and with substrates for periphyton (LDS). We calculated using emergy accounting the transformity (Tr), renewability (%R), emergy yield ratio (EYR), emergy investment ratio (EIR), emergy loading ratio (ELR), emergy exchange ratio (EER), and emergy sustainability index (ESI) of the distinct production managements. The results showed that tilapia cage farming is highly dependent on resources from economy, and feed is mainly responsible for this. Thus, the decrease in stocking density and feed rate, combined with the use of periphyton, improved all emergy indices evaluated. This occurred because there was a decrease in the use of resources from economy and increase in the use of renewable natural resources. The study shows through the emergy accounting that the use of periphyton to feed cultured fish combined with a reduction in artificial feed use and a decrease in the stocking density should be encouraged to promote the sustainability on tilapia cage farming.Published by Elsevier Ltd.

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The search for healthier protein sources and the growing demand for food by an increasing world population require aquaculture systems to not only be economically and technologically viable, but also sustainable. Among other methods, emergy synthesis is a powerful tool to assess the sustainability of production systems in a biophysical perspective. However, applications of emergy synthesis on aquaculture systems are seldomly found in the scientific literature. This work provides a literature review on emergy synthesis applied to aquaculture systems and discusses its constraints and potentials. The sixteen papers published between 2000‐2020 support the adoption of polycultures more than monocultures and highlight the importance of feed (4–70%) in the total emergy required by aquaculture systems, which require efforts for natural food. Methodological aspects of emergy synthesis applied in aquaculture systems that deserve attention by developers and analysts to avoid mistakes and erroneous conclusions were identified and discussed, and we propose some ways to solve them. These aspects are mainly related to inaccurate unit emergy values for water and feed, dubious procedures in quantifying and classifying water as renewable or non‐renewable resources, and the need to recognize the importance in accounting for ecosystem services and disservices. After overcoming these methodological inconsistencies, we foresee that emergy synthesis has potential political implications in supporting most sustainable aquaculture systems through economic (tax reduction and loans with reduced interests) and political (green labels) incentives. All these policies are important to achieve the ultimate goals of the United Nations’ Agenda 2030.

Aquaponics is emerging as an alternative for high-health food production. Being able to identify the technical viability of non-conventional plants and fish species would help to increase the interest and possibilities in aquaponic systems. The goal of the present study was to evaluate the aquaponics production of two garnish species: scallion (S) and parsley (P), using effluents of pacu and red tilapia culture. Two aquaponics devices were used, differing according to the fish species, generating two different effluents. Thus, for plant performance, four treatments were evaluated in a factorial design (plant species and fish effluent as main factors), as followed: Pacu-S, Tilapia-S, Pacu-P, and Tilapia-P, with three replicates each, for 35 days. Fish performance was evaluated using Student's t test. Each experimental device included a fish tank, filters, and six experimental units for the plants (floating rafts). Results

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Tilapia and catfish are the most popular fish species in aquaponics. However, they are not well-accepted in all markets, and finding alternative species is important in order to increase the variety of food products and meet market demands. South America has several potential fish species for aquaponics systems. Encouraging the implementation of integrated aquaculture systems by providing information about the production of South American species can help to increase the supply of high-quality food and aquaculture diversification. Thus, data for five South American fish species with potential for aquaponics were compared with existing data for the main traditional warm water species in this system, tilapia and catfish. Moreover, the degree of suitability of the novel species for these systems in terms of zootechnical performance, tolerance to water quality and nutritional composition of fish flesh were discussed. The South American species considered were jundia or silver catfish (Rhamdia quelen), yellowtail lambari (Astyanax lacustris), pacu (Piaractus mesopotamicus), tambaqui (Colossoma macropomum) and snook (Centropomus spp.). Their description and the tabular comparison with the most traditional aquaponic-cultured species show they are suited for this production system. How suitable they are will depend on the system design, as well as the regional characteristics of the market where they will be produced.