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.

Use of a novel induced spawning technique for the first reported captive spawning of Tetraodon nigroviridis.

The spotted green pufferfish (Tetraodon nigroviridis) is an important genetics model animal due to its small, well-mapped genome. However, only wild-caught juveniles and adults are available to researchers. A lack of gametes, fertilized eggs, developing embryos, and other early life stages hampers development of the full potential of T. nigroviridis as a model research species. We report on successful spawning trials using a novel induced spawning technique, ovarian lavage. Chorulon(®) (human chorionic gonadotropin, hCG) was injected into a catheter inserted into the oviduct at a rate of 3 µl/g body weight. In one trial, a female paired with a male spawned in an aquarium at about 72 h post-treatment. In other trials, females were hand-stripped of eggs at 36 h post-treatment. There were 3680 eggs/g of eggs and females produced up to 24% of their body weight in eggs. Hatch resulted from all trials on the 4th day post-fertilization. Ovarian lavage is a simple method for administering spawning hormones, uses a catheter technique similar to that frequently performed to determine egg maturity in broodstock, and eliminates the need for injection.