Integrated multitrophic cultivation of Litopenaeus vannamei and fish to control total suspended solids in a biofloc system

Author: Mariana Holanda Paes Barboza (Currículo Lattes)
Supervisor: Dr Luis Henrique da Silva Poersch

Abstract

Despite the benefits of the biofloc system, the combination of closed system and high storage densities results in the accumulation of total suspended solids throughout the cycle, as a consequence of the increase of microbial biomass, that take advantage of the carbon and nitrogen fertilized from organic fertilizations and excreta of animals. It is recommended that, for shrimp production, SST concentrations should be maintained between 100 and 300 mg L , when this value is reached the excess solids must be removed from the system, usually by use of clarifiers, generating effluents with high polluting potential of natural waters. The control of the total suspended solids excess (TSS) of shrimp production in the BFT system can be done by the integration of species that act at different trophic levels is called Integrated Multitrophic Aquaculture (IMTA) and is based on the concept that residues, as unused rations, feces and metabolic excretion of one species are useful to feed another species of a different trophic level. Chapter I and II of this thesis aimed to evaluate the functionality of the integrated multitrophic system, composed by Mugil. liza and Litopenaeus vannamei and Oreochromis. niloticus and L. vannamei, respectively, reared in a biofloc system. The objective of these chapters was to determine the best spatial arrangement for the animals for the best yield and utilization of the system. Two different experiments were carried out, one with mullets and one with tilapia, with three treatments each, being a control (monoculture of shrimp) one with fish and shrimp in the same tank (IMTA MT) the other with fish and shrimp in separate tanks in water recirculation system (IMTA DT). In both chapters, both mullet and tilapia affected shrimp growth in IMTA MT treatments, and fish consumed microbial flakes, controlling the excess of SST in the IMTA DT treatment, without jeopardizing shrimp performance. In Chapter III, two densities of tilapia were tested in the integrated culture with L. vannamei, 100 m-3 (IMTA 100) and 200 m-3 fish (IMTA 200), in addition to shrimp monoculture (Mono cam = 400 shrimp m -3) and monoculture of fish (Mono fish = 200 fish m-3). The results observed in this chapter show that the presence of fish at high densities affected nitrification in the BFT system, possibly due to the consumption of microbial flakes by the fish and consequent reduction of the substrate of the nitrifying bacteria. The IMTA 100 treatment was the one that presented the least time of clarification, proving the efficiency of the tilapia in the relationship biomass shrimp:fish more adequate (1:1) to consume the natural productivity of the system, controlling the excess of SST of the culture of L. vannamei in BFT system. The objective of this study was to evaluate the effect of the integrated superintensive cultivation of white shrimp L. vannamei and tilapia at different densities cultivated in a pilot scale BFT system in order to promote the maintenance of the levels of SST at the appropriate levels for the system of fish consumption. The experiment lasted 78 days and had two treatments: T35 (integrated shrimp culture (550 shrimp m-3) and tilapia at the density of 35 m-3 and T65 fish (integrated shrimp culture (540 shrimp m-3) and tilapia (4m3) and shrimp (10m3), and one tilapia (4m3) was used in the treatment of the two treatments (4.3 kg m-3), T35 was more efficient in relation to the shorter clarification time, but the T65 treatment presented higher productivity. It was concluded that the integrated cultivation of L. vannamei and M. liza and O. niloticus in a system BFT, fish are efficient in consuming and maintaining SST levels of L. vannamei culture in BFT system, contributing to making sea shrimp production more economically profitable and environmentally friendly.

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