Plasma Cortisol, Blood Glucose, and Marketability of Koi Transported with Metomidate Hydrochloride

The transportation of fish is stressful and may negatively affect their health, appearance, and marketability (i.e., their appearance, behavior, and activity level). The objective of this study was to determine whether sedation with metomidate hydrochloride during transportation would inhibit elevation of the plasma cortisol and blood glucose levels of koi, a strain of common carp Cyprinus carpio, and improve their marketability relative to that of transported control fish. The metomidate concentrations tested were 0 (control), 1.0, 2.0, 3.0, and 4.0 mg/L. The fish were transported for approximately 24 h via truck and domestic airline under typical shipping conditions. Blood was sampled at 0, 2, 6, and 12 h posttransportation, and appearance and behavior were observed at 0, 1, 4, 8, and 12 h and 7 d posttransportation. Immediately after transport, the plasma cortisol levels of koi in metomidate concentrations of 3.0 and 4.0 mg/L were significantly lower than those of the controls, but no differences were observed in blood glucose levels among the various metomidate treatments. Also, there were no differences in the appearance and behavior scores among transported fish, but the scores of koi transported in 0 and 4.0 mg/L were significantly lower than those of nontransported koi at 0 h posttransportation. In this experiment, a metomidate concentration of 3.0 mg/L had a transient inhibitory effect on plasma cortisol and did not have an adverse effect on appearance or behavior; it therefore represented the best concentration for the transportation of koi among those tested. However, more research is required to fully understand the effects of metomidate exposure on koi.