Quantificação da contribuição da microalga Navicula sp. no cultivo de Litopenaeus vannamei (Boone, 1931) em sistema de bioflocos usando isótopos estáveis.

Abstract

The present project was based on the completion of two studies: a bibliometric study and a cultivation experiment. Aquaculture plays a fundamental role globally as a source of food and sustenance. Stable isotope analysis, especially of carbon and nitrogen, is a powerful tool for understanding the food sources of aquatic organisms, tracing fishery products, comprehending interactions in aquatic food chains, and conducting environmental studies. The bibliometric study addressed five questions related to the use of stable isotopes in aquaculture and revealed a steady increase in the number of publications over time, with Europe, Asia, and North America leading the research. Institutions such as the Ocean University of China and researchers like Shuang-Lin Dong and Antonio Mazzola stood out in this field. The main topics included aquaculture, effluents, stable isotopes, nitrogen, and diet. This research highlighted the growing importance of stable isotopes in aquaculture, encompassing nutritional aspects, traceability, and environmental impact. On the other hand, the cultivation experiment assessed the impact of adding the diatom Navicula sp. to biofloc nursery systems of Penaeus vannamei shrimp. The study aimed to understand whether the microalga is part of the microbial floc or is directly consumed by the shrimp, analyzing its nutritional contribution to shrimp growth. Over 35 days, shrimp were reared in biofloc systems at a stocking density of 3000 post-larvae per cubic meter, with the addition of Navicula sp. at different frequencies. The results showed similar survival rates in all treatments (~93%), but there was a significant difference in weight gain and feed conversion ratio. The N10 treatment (0.50 ± 0.05 g, 0.99 ± 0.01) exhibited better growth parameters compared to the WN treatment (0.33 ± 0.07 g, 11.46 ± 0.30), which did not receive Navicula sp. addition. Isotopic analysis indicated that biofloc was the most assimilated food source by the shrimp, followed by Navicula sp. and commercial feed. Navicula sp. contributed more in the N5 treatment. Furthermore, the results revealed an inverse correlation between the relative contributions of biofloc and Navicula sp. in treatments with diatom addition, suggesting that Navicula sp. is not part of the biofloc composition and is directly consumed by P. vannamei post-larvae. In summary, biofloc and Navicula sp. played significant roles in shrimp growth, emphasizing the importance of natural food sources in the aquaculture of P. vannamei post-larvae.