Integrated multi-trophic aquaculture (IMTA) outperforms conventional polyculture with respect to environmental remediation, productivity and economic return in brackishwater ponds

Abstract

Any sustainable aquaculture system should have low environmental impact, and high social and economic acceptability. To address these issues in brackishwater aquaculture, performance of integrated multi-trophic aquaculture (IMTA) models with three different species combinations (T1, T2 and T3) was compared with conventional polyculture (C) in low-saline ponds (500 m2) in triplicate. In a 150-day field trial, ponds under T1, T2, T3 and C were stocked with Mugil cephalus, Liza tade and Peneaus monodon at 2000, 10000 and 30000 no. ha−1, respectively as fed-species. In addition, T1 and T3 contained water spinach, Ipomoea aquatica at 200 kg ha−1, and T2 and T3 contained oyster, Crassostrea cuttackensis at 2000 no. ha−1 as extractive species. Experimental animals were fed with a low cost pellet feed (Crude protein 31%). The inorganic nutrient parameters (nitrogenous and phosphorus compounds) of water improved in all three IMTA treatment ponds in comparison to C. On the final day, dissolved organic carbon content was significantly the lowest (P < 0.05) in T3 (9.39 ± 0.61 mg L-l), compared to that in C (13.73 ± 1.27 mg L-l). Similarly, particulate organic matter content was also significantly the lowest (P < 0.05) in T3 (61.33 ± 5.75 mg L-l) among all the treatments. Chlorophyll-a content in pond water of IMTA treatments (T2 and T3) with oyster was significantly low (P < 0.05) compared to that in C (0.048 ± 0.009 mg L-l) and T1 (0.040 ± 0.002 mg L-l) on the final day. Final body weight of M. cephalus (118.10 ± 7.29 g) and L. tade (25.41 ± 1.54 g) was not significantly (P > 0.05) higher in T3 compared to that of T1, T2 and C. However, growth of tiger shrimp, P. monodon was significantly higher (P < 0.05) in T3 (22.17 ± 1.29 g). Pooled survival of fishes and shrimp was similar among treatments, whereas total production was significantly higher (P < 0.05) in T3 (1695.7 kg ha−1), followed by that in T1 (1211.9 kg ha−1), T2 (894.2 kg ha−1) and C (505.4 kg ha−1). Overall, whole body composition of fishes and shrimp at harvest revealed that crude protein and lipid contents were marginally at higher levels in IMTA treatments compared to that of C. There were 3.48 and 1.6-fold increases in net return and benefit-cost ratio, respectively in T3 than that in C. Therefore, this IMTA model (T3) proved to be productive, and economically viable with environmental bio-remediation effect.