Effects of Tricaine Methanesulphonate (MS-222) on Physiological Stress and Fresh Quality of Sea Bass (Lateolabrax maculatus) under Simulated High-Density and Long-Distance Transport Stress

SIMPLE SUMMARY: The traditional method of transporting live fish in water often involves long driving durations and a high transport density. These conditions not only cause the deterioration of transport water quality but also induce stress in fish, seriously affecting their physiological and metabolic responses. At the same time, it also causes changes in the flavor of fish muscle. In this study, methanesulphonate (MS-222), a common anesthetic, was applied to live fish during transportation in order to slow down the deterioration of the water environment quality, reduce the stress response of sea bass, and improve meat flavor. The effects of different transport densities on water quality, oxidative stress, energy metabolism, and meat flavor of sea bass were measured under the conditions of adding MS-222 concentration of 30 mg/L and different transport densities for 72 h, and these effects were compared with those without MS-222. The results showed that the water quality, oxidative stress, and energy metabolism of anesthetized fish were lower than those of the control group at the same density. The addition of 30 mg/L MS-222 to stabilize fish under high density transportation can reduce the deterioration of water quality and the effect on the stress of live fish, and improve meat flavor. ABSTRACT: This study aimed to evaluate the effect of different transport densities on water deterioration, physiological response, nutrients, and fresh quality of sea bass (Lateolabrax maculatus) at 30 mg/L tricaine methanesulphonate (MS-222) before and after simulated live transport. The results indicated that the addition of MS-222 could effectively decrease mortality compared with the control (CK) sample during the simulated live transport. The concentration of dissolved oxygen was lower and the total ammonia nitrogen was higher in the high transport density samples than those of low transport density samples after 72 h in transport. The level of blood cortisol (COR), glucose (GLU), lactic acid (LD), aspartate aminotransferase (AST), alanine aminotransferase (ALT) for the sea bass were significantly higher compared with the CK sample (p < 0.05) during the simulated live transport and after 12 h of recovery. These results indicated that the sea bass presented a strong stress response in high-density transport. The glycogen, fat, and protein of the sea bass were degraded to supply the energy for the body in the process of surviving the transportation, resulting in the decreased nutrient content in the muscle, which recovered to the initial level (CK) after 12 h. The increase in flavor substance content, such as free amino acids, nucleotides, organic acids, and minerals, enhanced the special flavor of the muscle during the simulated live transport. This study demonstrates that the addition of MS-222 at 30 mg/L to the transport water is an effective method for live fish to realize low mortality and physiological response during high-density and long-distance transport.