Effects of Ammonia-Nitrogen-Reducing Biofilm on Stress Responses and Muscle Quality in Crucian Carp During Transportation

Abstract

This study evaluated the efficacy of ammonia-nitrogen-reducing biofilms (aquatic nitrifying bacteria biofilm media, a fixed-bed biofilm capable of simultaneous nitrification and denitrification) in mitigating water quality deterioration and transport-induced physiological stress in live-transported Crucian carp (<i>Carassius auratus</i>). In a simulated bag transport system, the application of the biofilm significantly decreased ammonia-nitrogen concentrations through enhanced nitrification, stabilized pH and dissolved oxygen dynamics, and suppressed nitrite accumulation. Correspondingly, biofilm-treated fish exhibited significantly reduced systemic stress responses, as evidenced by reduced serum cortisol, glucose, and lactate dehydrogenase concentrations, along with diminished histopathological changes in gill and liver tissues and preserved muscle fiber integrity. Regarding post-transport muscle quality, biofilm treatment delayed glycogen catabolism and lactate accumulation, maintained elevated muscle pH and water-holding capacity, reduced shear force decline, decelerated ATP hydrolysis and freshness degradation (K-value), and simultaneously suppressed lipid peroxidation and myonuclear apoptosis. These findings demonstrate that ammonia-nitrogen-reducing biofilms represent a viable biotechnological approach for maintaining water quality, mitigating stress-induced physiological disturbances, and preserving flesh quality during live fish transportation. This approach has significant potential for improving post-harvest outcomes in aquaculture logistics.