Pre-Transport Salt Baths Mitigate Physiological Stress and Tissue Damage in Channel Catfish (Ictalurus punctatus) Fingerlings: Evidence from Multi-Biomarker Assessment and Histopathology.

Effective transport strategies are critical for the survival and welfare of juvenile Ictalurus punctatus, but the effects of pre-transport salt bath treatments remain uncertain. In this study, we systematically evaluated the effects of pre-transport salt bath acclimation at 0‱ (S1), 1‱ (S2), 5‱ (S3), and 9‱ (S4) salinity for 30 min on stress resilience and recovery in fingerlings during 12 h of simulated transport and 24 h of recovery. All fish survived, but total ammonia nitrogen (TAN) increased, and pH decreased in all groups, except S3, which showed significantly lower TAN and higher pH (p < 0.05). The S3 and S4 groups showed attenuated increases in serum cortisol and glucose, with S3 exhibiting the fastest return to baseline levels and stable serum sodium and potassium levels. Liver antioxidant enzyme activities in group S3 remained stable, with the lowest malondialdehyde (MDA) accumulation. Integrated biomarker response (IBR) and histological analyses demonstrated that S3 had the lowest systemic stress and tissue damage, whereas S1 and S4 displayed marked cellular disruption. These results indicate that a 5‱ salt bath applied prior to transport may improve water quality, mitigate stress responses, and preserve tissue integrity in juvenile channel catfish. Further studies are needed to confirm these findings in other species and under commercial transport conditions.