Introduction
According to the UN (2019), there are predictions that we can reach up to 10 billion people in 2050. Aquaculture can help overcome the protein deficit generated by the high population. For this, the production of aquatic organisms should increase, and thus, it is essential to use effective production systems to prevent adverse effects on the producer, the environment, or society (SAAD et al., 2018). In this way, farming low trophic species may be more sustainable than farming high trophic species. In this study, environmental sustainability indicators of producing organisms (macroalgae), filter feeders (oysters), and allochthonous food ingesters (low trophic level fish) were comparatively analyzed using a benchmark framework.
Materials and methods
Secondary data were compiled for 19 environmental sustainability indicators (Valenti et al., 2018) previously obtained for seven aquaculture systems. Five are monocultures. They include the farming of the macroalgae Hypnea pseudomusciformes (Pereira et al., 2021), the oyster Crassostrea gasar in tropical (Sampaio et al., 2023) and in subtropical regions (Miraldo, 2015), the fish tambatinga, a hybrid of Colossoma macropomum and Piaractus brachypomus (Gilson, 2019), and tambaqui, Colossoma macropomum (Dantas, 2017). Two are integrated systems: tambaqui in hapa inside Amazon river prawn (Macrobrachium amazonicum) ponds (Tambaqui IMTA-Hapa) and tambaqui and Amazon river prawn both free in ponds (Tambaqui IMTA-Free) (Dantas, 2017). These seven systems were used as models to assess the environmental sustainability in low trophic species aquaculture. The benchmark tool was applied, establishing reference values for comparing indicators between the systems.
Results
Macroagae showed the highest sustainable score for ten indicators, tropical and subtropical oysters for seven, and tambatinga for one. Tambaqui IMTA-Hapa received the lowest score for eight indicators, subtropical oyster for six, tambatinga and tambaqui monoculture for three, and Tambaqui IMTA-Free and tropical oyster for two.
Discussion
Environmental sustainability showed different patterns in the culture of organisms from different trophic levels. Considering the culture models used in the present study, environmental sustainability seems to decrease as the farmed species’ trophic level increases. Integrated low-trophic fish farming systems did not show environmental sustainability superior to monocultures, as could be anticipated. Nevertheless, comparison between production systems is complex due to their large variations. The tremendous biological differences between cultivated species require very different culture systems. In addition, there are various levels of intensification, feeding, and management to maintain water quality. The sustainability indicators measure common points in different farm systems necessary for sustainability analysis. The difficulty in comparing them in an integrated way arises from using variables of various dimensions and unities. Therefore, a standardization and integration technique is needed. Generally, the benchmark analysis met this need. It effectively showed the differences between the indicators in the various analyzed systems in a more accessible and standardized way.
Conclusion
The benchmarking framework carried out with seven aquaculture systems indicated that macroalgae, tropical, and subtropical oyster cultures are more environmentally sustainable than low trophic level fish cultures. The cultures of these extractive organisms do not depend on the supply of an allochthonous diet and are performed at sea. Integrated low-trophic fish farming systems have not shown environmental sustainability much superior to monocultures as expected. Indeed, the culture designs and the species used play a preponderant role in the sustainability of the aquaculture systems.
Using the benchmark framework proposed in the current study effectively ranks the production systems according to each indicator, allowing quick visualization. The magnitude of the differences in an indicator in the various systems is somewhat masked by standardization when there is a substantial asymmetry in the distribution of the numerical values. Modifications in the standardization formulas should be studied to make it easier to see the differences.
References
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(AquaVitae – Horizon 2020; Sustainable Aquaculture Network; CNPq; FAPESP)