COMPARISON OF THREE CONCENTRATIONS OF AQUA-SEDTM FOR IMMERSION EUTHANASIA OF BUTTERFLY SPLITFIN (AMECA SPLENDENS).

The efficacies of three concentrations of 2-phenoxyethanol from Aqua-sedTM were examined to determine the suitability for euthanasia of butterfly splitfin (Ameca splendens). Thirty fish were randomly assigned to be immersed in one of three Aqua-SedTM concentrations: 0.5, 2, and 6 ml/L. Opercular rates and caudal fin stroke rates were quantified, and time to the cessation of physiological measures including heartbeat, caudal fin strokes, reaction to external stimuli, righting reflex, swimming, and operculation were recorded. To test for the effects of concentration of Aqua-sedTM on all times to cessation of physiological measures, a linear mixed model was performed followed by pairwise comparisons with a Bonferroni correction. A proportions test compared the number of fish that lost their heartbeat across Aqua-sedTM concentrations. Varying anesthetic induction times were observed for all three Aqua-sedTM concentrations; time to cessation of physiological measures was fastest with 6 ml/L, followed by 2 then 0.5 ml/L, but only concentrations of 2 and 6 ml/L induced anesthesia in less than the recommended 180 s. Aqua-sedTM concentration had a significant effect on time to cessation of physiological measures (P < 0.01), but not on time to cessation of a heartbeat (P > 0.05). Pairwise comparisons indicate time to cessation of caudal fin strokes, reaction to external stimuli, righting reflex, and swimming significantly decreased as concentration increased (P < 0.01). After 60 min of immersion in Aqua-sedTM the number of fish without a heartbeat differed significantly across concentrations (P < 0.01); 20% of fish immersed in 0.5 ml/L, 90% of fish immersed in 2 ml/L, and 90% of fish immersed in 6 ml/L had no heartbeat. A minimum dose of 2 ml/L of Aqua-sedTM, and an immersion time of 60 min for euthanasia of butterfly splitfin is recommended, with a secondary euthanasia measure to confirm death when the heartbeat remains.

USE OF TRICAINE METHANESULFONATE, CLOVE OIL AND 2-PHENOXYETHANOL FOR IMMERSION EUTHANASIA OF UNGA CICHLIDS (SAROTHERODON LINELLII).

Fish may warrant euthanasia for a variety of reasons, but euthanasia may be difficult to accomplish or confirm because fish can recover from deep anesthesia even after cardiac and respiratory arrest. The efficacies of three types of anesthetics were evaluated to compare their suitability for euthanasia of Unga cichlids (Sarotherodon linellii). Thirty cichlids were randomly assigned to be immersed in one of the three anesthetic solutions: tricaine methanesulfonate (MS-222), 2-phenoxyethanol (2-PE), and clove oil (CO) at doses of 1,000 mg/L, 2 mL/L, and 500 mg/L respectively. The opercular rates and caudal fin stroke rates were quantified, and the time to cessation of physiological measures (CPM) including caudal fin strokes, the reaction to external stimuli, the righting reflex, swimming, and operculation were recorded. Varying anesthetic induction times were observed with all three euthanasia solutions; the time to CPM in the 2-PE group occurred at a significantly slower rate than in the MS-222 group (P < 0.01). No significant differences were identified for the time to CPM when comparing the standard length or weight of the cichlids in all euthanasia solutions (P > 0.05). The cost of euthanasia per cichlid was calculated, with the most economically viable option being 2-PE; at more than seven times the price of 2-PE, MS-222 was the most expensive. After a 60-min immersion in the euthanasia solution, the presence of an audible heartbeat was identified in 100% of the cichlids immersed in 2-PE, 100% immersed in CO, and 90% in MS-222, indicating that they were not reliably euthanized. Therefore, a two-step protocol is recommended in cichlids for euthanasia: heavy anesthesia via immersion followed by an intravenous or intracardiac injection of euthanasia solution, or other secondary method of euthanasia.