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

## TL;DR

A short salt bath before transporting young channel catfish reduces stress and tissue damage, improving survival rates.

## Contribution

This study demonstrates that a 5‰ salt bath before transport mitigates stress and tissue damage in juvenile channel catfish.

## Key findings

- A 5‰ salt bath significantly reduced ammonia and improved pH during simulated transport.
- The 5‰ salt bath minimized stress hormones and preserved liver function in fish.
- Histological analysis showed the 5‰ salt bath caused the least tissue damage.

## Abstract

Transporting juvenile Ictalurus punctatus is an important step for fish farmers, but it can cause stress that affects fish health and survival. In this study, we used a simulated transport to test if giving fish a salt bath before moving them could make a difference. We tested different salt bath concentrations and found that a short salt bath with 5‰ salinity before transport helped maintain better water quality, reduced stress, and protected the fish’s tissues. This simple and low-cost method can help fish farmers improve survival rates and reduce losses during live fish transport.

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.