Integrated mariculture of co-cultured whiteleg shrimp (Litopenaeus vannamei) and grey mullet (Mugil cephalus) in sequence with red tilapia (Oreochromis spp.) in a closed biofloc-based system

A tri-species integration of shrimp and finfishes, using a closed integrated multi-trophic aquaculture (IMTA) sequential biofloc system, aiming at optimizing the performance of intensive shrimp farming was evaluated by an indoor lab-scale experiment lasting for 50 days. The impact of this integration on production and environmental efficiency was investigated. Furthermore, the optimum initial red tilapia biomass, as a third extractive species, was explored. The IMTA recirculating sequential system consisted of a cultivating tank (800 L) for whiteleg shrimp (Litopenaeus vannamei) and grey mullet (Mugil cephalus) co-culture, connected to an adjacent red tilapia (Oreochromis spp.) cultivating tank (90 L). Shrimp (0.50 +/- 0.17 g), as the main crop, with mullet (1.00 +/- 0.53 g) were stocked at the density of 200 shrimps.m(-3) and 10% of the initial shrimp biomass, respectively. Meanwhile, two different densities of red tilapia were investigated in conjunction with the treatments, each in triplicate, of (i) control: shrimp-mullet without tilapia; (ii) BSM-10T: shrimp-mullet with 10 tilapias; and (iii) BSM-20T: shrimp-mullet with 20 tilapias. No external feed was provided for the finfishes throughout the experiment, enforcing tilapia to grow on bioflocs only. The results demonstrated that the addition of red tilapia at a proper proportion to the tri-species closed integration system resulted in positive effects on the cultured organism's performance. The physicochemical water parameters such as TAN, NO2--N, NO3--N, and PO43--P were significantly lower (p < 0.05) in the BSM-10T and BSM-20T than in the control treatment. The statistical optimum (p < 0.05) of shrimp growth rate (0.19 +/- 0.01 g. day(-1)), overall biomass (1521.30 +/- 88.47 g.tank(-1)), and FCR (0.95 +/- 0.05) was achieved in the BSM-10T treatment. Superior microbial loading (p < 0.05) and shrimp digestive enzyme activities were detected in the BSM-10T treatment. The overall nitrogen and phosphorus recovery was statistically higher (p < 0.05) in the tri-species integrated culture groups (N: 38.53 +/- 1.20-46.19 +/- 1.75%; P: 33.09 +/- 2.20-33.63 +/- 3.69%) than in the bi-species polycultured group (N: 31.91 +/- 3.13%; P: 19.30 +/- 2.15%). The present study demonstrated that the tri-species integration of shrimp and mullet with red tilapia, introduced at an optimal initial density of 0.17 kg.m,(-3) employing a closed IMTA sequential biofloc system can be practically and feasibly applied to ameliorate water quality in addition to increasing overall animal production, and improving nutrient utilization efficiency for the intensive shrimp aquaculture.