Evaluating circular bioeconomic performance and nutrient recycling in tarpaulin-tank hybrid grouper nursery under integrated multi-trophic aquaculture

Abstract

Sustainable marine fish nurseries require production strategies that maintain juvenile performance while improving the recovery and valorization of residual resources. This study evaluated whether different integrated multi-trophic aquaculture (IMTA) configurations could shift hybrid grouper (Epinephelus fuscoguttatus × E. lanceolatus) nursery culture in tarpaulin tanks from a linear toward a semi-circular production pattern. A 28-day experiment compared four systems: grouper monoculture (K), grouper–sandfish sea cucumber–mussel (A), grouper–sandfish sea cucumber–seaweed (B), and grouper–sandfish sea cucumber–mussel–seaweed (C). Biological performance, water-quality responses, waste reduction, resource valorization, and economic circularity were evaluated. Most growth, survival, and feed-utilization parameters did not differ significantly among treatments; however, the coefficient of variation in body length was significantly lower in all IMTA treatments than in monoculture (p = 0.022), indicating greater size uniformity. The derived Solid Waste Reduction Relative to Monoculture was highest in treatment B (54.14%). Treatment A showed the highest Waste-to-Value Conversion (USD 0.097 g⁻1 waste reduced) and Economic Circularity Ratio (76.97%), together with the lowest Total Economic Value Loss (USD 7.62), whereas treatment C showed the highest proportional contribution of co-products to system value. Dissolved nutrient responses were less consistent, indicating incomplete nutrient recovery during the 28-day culture period. Overall, the results show that circular performance was multidimensional and configuration-dependent: the treatment associated with the greatest material waste reduction was not the same as that showing the highest economic value recovery. Based on the circularity framework applied in this study, monoculture was classified as linear, whereas all IMTA configurations were classified as semi-circular. IMTA was associated with greater body-length uniformity in hybrid grouper juveniles. Solid-waste reduction relative to monoculture reached 54.14% under IMTA. Waste-to-Value Conversion reached USD 0.097 g⁻1 of waste reduced. Deposit feeder–filter feeder integration showed the most favorable numerical economic profile. Circular performance was multidimensional and configuration-dependent across IMTA treatments.