Introduction
Nursery systems using biofloc technology have proven effective in boosting productivity, improving survival, and minimizing environmental impacts in shrimp farming. However, in subtropical regions, cold fronts during autumn and winter pose a growing challenge by lowering temperatures, which negatively affect shrimp health and growth. Recently, macroalgae have gained attention as feed additives due to their nutritional value and their immunostimulant, antiviral, antibacterial, and growth-enhancing properties, offering a sustainable alternative to antibiotics in shrimp aquaculture. This study aimed to assess the effects of including dry biomass of the green macroalga Ulva ohnoi in the diet of Penaeus vannamei post-larvae reared in a biofloc system, focusing on growth performance, post-larvae microbiology, and thermal shock resistance.
Material and methods
The study was conducted at the Marine Shrimp Laboratory, Department of Aquaculture, Federal University of Santa Catarina, Brazil U. ohnoi was sourced from an integrated multitrophic aquaculture system using biofloc technology , included in diets at three levels (0, 0.5, and 2% inclusion) and added to diets to replace kaolin. Post-larvae , with an initial mean weight of 0.068 ± 0.01 g , were reared for 46 days in 60-L tanks at a density of 2,000 shrimp m-3 and fed six times a day. The nutritional requirements of P. monodon were used as a reference for formulating diets for P. vannamei.
Results
Temperature was kept at 28 °C and dissolved oxygen above 5 mg L-1 in all treatments . No significant differences were observed among treatments for total ammonia nitrogen, nitrite, nitrate, alkalinity, pH, total suspended solids, or salinity. Shrimp fed with 0.5% of U. ohnoi in diet showed significantly higher final mean weight (an 18.7% increase), weight gain, and growth rate than those in the control group , without affecting survival or feed conversion ratio. Increasing the levels of U. ohnoi in the diets led to a rise in the abundance of heterotrophic bacteria in shrimp, with the 2% inclusion treatment showing a significantly higher bacterial count compared to control group. Although a numerical reduction in Vibrio spp. was observed in shrimp fed with algae-supplemented diets, this decrease was not statistically significant when compared to control. Additionally, the inclusion of U. ohnoi had no effect on the thermal resistance of shrimp reared in the biofloc system over the 46-day period.
Conclusions
Considering shrimp performance was similar across diets containing U. ohnoi , the inclusion level of 0.5% is recommended, as it resulted in higher growth rates compared to control group.
Acknowledgements
This research was financed in part by the Research and Innovation Support Foundation of Santa Catarina (FAPESC, project 2020TR728) and the Coordination for the Improvement of Higher Education Personnel (CAPES, Brazil, Finance Code 001).
Note
This abstract summarizes the findings from the published article:
Santos, I. L., Carneiro, R. F. S., Morais, A. P. M., Martins, M. A., Seiffert, W. Q., & Vieira, F. N. (2024). Ulva ohnoi as a feed additive for Pacific white shrimp post-larvae cultured in a biofloc system. Aquaculture International, 32, 8809–8822. https://doi.org/10.1007/s10499-024-01591-4