Evaluation of efficacy of vermicompost application to aquaculture wastewater and its impact on growth performance of Channa striata and Lactuca sativa L. in aquaponics

Abstract

The growth response of Channa striata and Lactuca sativa L. was evaluated in an aquaponics supplemented with vermicompost at five dosages, viz., 14.4, 21.6, 28.8, 36.0, and 43.2 mg/L designated as verm14.4, verm21.6, verm28.8, verm36.0, and verm43.2, respectively. The aquaponics was stocked with Channa striata at 2.24 kg/m³ (average weight = 6.05 ± 0.06 g) and lettuce at 28 plants/m² in nutrient film technique (NFT) hydroponics. The water quality characteristics were within an acceptable range except for higher nitrite in verm36.0 and verm43.2. The fish growth parameters exhibited no significant difference and followed the order: verm21.6 (69.29 ± 1.19 g) > verm28.8 (68.82 ± 1.16 g) > verm36.0 (67.72 ± 1.56 g) >  verm14.4 (66.71 ± 1.32 g) > verm43.2 (66.31 ± 1.54 g). The physiological traits namely serum alanine transaminase (ALT), serum aspartate transaminase (AST), superoxide dismutase (SOD), and catalase (CAT) in the liver were significantly higher in verm43.2, while no significant variation was observed in either SOD or CAT in the gill. Though a higher magnitude of cortisol was recorded in verm36.0 and verm43.2, no significant difference (p > 0.05) was apparent in serum glucose levels in fish. The total lettuce yield followed the order: verm21.6 (819.67 ± 9.22 g) > verm28.8 (796.70 ± 24.61 g) >verm36.0 (730.30 ± 10.22 g) > verm43.2 (702.47 ± 14.06 g) >verm14.4 (697.90 ± 6.10 g), indicating that the higher dosage had no significant output. The nutrient content of lettuce followed a similar trend to plant growth. Based on the two distinct quadratic regression models, the relationships between vermicompost dose with percentage weight gain of fish and lettuce biomass were estimated to be 27.4 and 27.6 mg/L, respectively; hence, 27.5 mg/L is recommended as the best compromise for overall system efficacy.