Investigational Use of Metomidate Hydrochloride as a Shipping Additive for Two Ornamental Fishes

During shipping, ornamental fish can be stressed due to handling, high stocking densities, and deteriorating water quality. Adding sedatives, such as metomidate hydrochloride, to shipping water may improve fish survival rates and the percentage of fish in saleable condition. Although the effects of metomidate hydrochloride on the stress response in fish have been studied, its application as a shipping additive has not been well investigated, particularly for tropical ornamental fishes shipped under industry conditions. Convict cichlids Cichlasoma nigrofasciatum and black mollies Poecilia sphenops were evaluated for 7 d after a 24‐h period of exposure (including ground and air transport) to one of four metomidate hydrochloride concentrations: 0.0, 0.2, 0.5, and 1.0 mg/L. Immediate posttransport and cumulative mortality data, as well as 12‐h and 7‐d posttransport appearance and behavior scores, were generated. In convict cichlids, the highest dose of metomidate hydrochloride (1.0 mg/L) reduced mortality (0% compared with cumulative means of 5.5–9.2% in other groups) and increased the percentage of saleable fish (91.7% were immediately saleable compared with 12.5–50% in other groups). No effect was detected in black mollies at any concentration tested. Metomidate hydrochloride showed promise as a shipping additive for convict cichlids, but further studies are warranted to evaluate species‐specific responses in other ornamental species.