Shrimp production in biofloc systems generates excess organic matter that must be removed from the system. Due to its ability to consume natural productivity, the integration of tilapia could help reduce the levels of total suspended solids.
Researchers from the Pontificia Universidad Católica de Valparaíso, the Norwegian Research Center, Climate & Environment and the Federal University of Rio Grande evaluated the effect of different fish culture densities on the integrated super-intensive culture of shrimp Litopenaeus vannamei and Nile tilapia (Oreochromis niloticus ) in a biofloc system to maintain total suspended solids (TSS) at appropriate levels for shrimp culture.
Difficulties of shrimp culture in biofloc
Shrimp production in biofloc systems has numerous economic advantages. However, there are environmental challenges such as the accumulation of organic matter during production in a system with minimal water exchange.
This accumulation produces an excess of suspended solids, which increases the biological oxygen demand due to the high concentration of aerobic microorganisms present in the biofloc.
In this sense, it is recommended that the excess total suspended solids (TSS) in the biofloc system be removed through clarification processes.
Evaluated crop densities
The researchers used two stocking densities: 35 (T35) and 65 (T65) fish/m3, in a recirculating system with 10 m3 tanks for shrimp culture and 4 m3 for tilapia culture.
Shrimp were fed according to the feeding table, while tilapia were underfed to stimulate biofloc consumption.
Benefits of using tilapia
“The presence of tilapia in the system does not negatively affect shrimp yield, regardless of the fish densities used,” they report.
According to the study, shrimp productivity was high, approximately 7.0 kg/m3, which is above the productivity values reported in studies evaluating vannamei shrimp monoculture in bioflocs on a pilot scale.
“Even when the tilapia was underfed, it showed a zootechnical performance similar to that reported for tilapia culture in the biofloc system,” they highlighted.
According to the results of the study, the tilapias presented a feed conversion factor of less than 1, indicating that the biofloc was consumed by the fish.
Regarding the L. vannamei shrimp, the feed conversion factor was similar to other studies with monoculture in a biofloc system.
Integration Benefits
“The values obtained in the present study are not only beneficial from the environmental point of view, but also economically advantageous since they can reduce production costs due to the reduction of the feed used, producing two species at the same time”, the researchers report. .
According to the results, tilapias can feed on bioflocs and the integration of the two species in an IMTA system could be implemented to ensure a more sustainable culture system.
Sedimentation time
Despite the integration of the fish into the system, the researchers had to remove excess total suspended solids through the sedimentation process.
“Sedimentation time was different in the two treatments, with T65 requiring more time, probably due to the high total biomass in this treatment,” they reported.
In the study, the lower density of tilapia in T35 requires a shorter clarification time (36 hours), which corroborates that the higher densities of fish culture can contribute to the excess of organic matter in the water.
“The study provides useful information for the implementation of biofloc farming with shrimp and fish in integrated farming systems, diversifying production without loss in yield of the target species”, they highlight.
Conclusion
“The results demonstrate the feasibility of integrating shrimp and tilapia farming on a pilot scale, without compromising shrimp productivity,” they concluded.
They also describe that when higher densities of tilapia are used (65 fish/m3), there is an increase in the concentrations of total suspended solids in the water.
“This pilot-scale study demonstrates that biofloc-based tilapia integrated multitrophic aquaculture (IMTA) systems with L. vannamei diversify production without compromising shrimp productivity,” they concluded.
The study had the financial support of the European Community (ASTRAL Project – H2020), the National Council for Scientific and Technological Development (CNPq) and the Coordination for the Improvement of Higher-Level Personnel (CAPES).
Reference (free access)
Holanda, M., Ravagnan, E., Lara, G., Santana, G., Furtado, P., Cardozo, A., & Poersch, L. H. (2023). Integrated multitrophic culture of shrimp Litopenaeus vannamei and tilapia Oreochromis niloticus in biofloc system: A pilot scale study. Frontiers in Marine Science.
