Anesthetic efficacy of two plant phenolics and the physiological response of juvenile Ictalurus punctatus to simulated transport

Abstract

The live transport of juvenile channel catfish (Ictalurus punctatus) is an important part of channel catfish breeding in China, but the anesthetic dose and physiological response of channel catfish after transport have not been studied yet. The purpose of this study was to assess the potential of eugenol and thymol in live transport and study their anesthetic effects of on juvenile channel catfish by analyzing a large number of parameters associated with stress and nonspecific immunity. First we tested eugenol and thymol concentrations of 10, 20, 30, 40, 50, and 100 mg/L. Eugenol successfully anesthetized the experimental fish at concentrations of 30–100 mg/L for 1258–82 s (resuscitation time was 147–300 s), while thymol was effective at 20–100 mg/L for 1612–81 s (recovery time was 333–475 s). The second experiment involved adding 10 and 20 mg/L of eugenol and thymol (4 groups) to the water, simulating transport (5 h), analyzing the stress and non-specific immune parameters of the serum, and determining gene expression changes in the liver and head kidney for 48 h. Anesthetics in the transport water inhibited the increase in serum cortisol levels (treatment group: 39.81–60.79 ng/mL, control group: 142.14 ng/mL), and Hsp90 in the liver was a more suitable biomarker for transport stress in channel catfish than Hsp70. Concentrations of serum total Ig, lysozyme, lectin, and ACH50, as well as the expression levels of cytokines (IL-1β, IL-8, and TNF-α) and pattern recognition receptors (NOD-1) in the head kidney increased. The expression of cytokines and NOD-1 in the head kidney returned to the pre-transport level after 48 h. Both anesthetics are suitable for channel catfish, but thymol is more suitable as a transport sedative. The results of this study could help maintain the health of juvenile channel catfish after live transport, decrease their infection and mortality, improve wellbeing, and reduce economic losses to the aquaculture industry.