A COMPARISON OF ALFAXALONE AND TRICAINE METHANESULPHONATE (MS-222) IN TWO FISH SPECIES

The purpose of this study was to evaluate the effectiveness of the alfaxalone formulation Alfaxan? as an immersion anesthetic in tropical fish species compared to that of tricaine methanesulfonate (MS-222). 22 black spot barbs (Puntius filamentosis) measuring (mean±SD) 11.4 ±1.4 cm in body length and 22 peacock cichlids (Aulonocara spp.) (measuring 8.4 ± 1.6cm were anesthetized in water baths containing 100 mg/L of MS-222 buffered with 200 mg/L of bicarbonate or 5 mg/L of alfaxalone following a 2-week washout period. Time to maximum effect, recovery periods, self-righting, spontaneous swimming movements, opercular movements, and response to noxious stimuli were recorded. The following results are for the black spot barbs following MS-222 and alfaxalone anesthesia, respectively: mean times (±SD) to surgical anesthesia were 5.5 ± 2.11 and 3.27 ± 1.72 minutes and mean recovery times were 2.95 ± 0.9 and 9.14 ± 3.15 minutes. The peacock cichlid anesthetic protocols for MS-222 (20 of 22 cichlids) and alfaxalone (20 of 21 cichlids) produced the following results, respectively: mean times (±SD) to surgical anesthesia were 14.75 ±5.43 and 11.1 ± 9.84 minutes and mean recovery times were 3.6 ±0.82 and 22.4 ±11.3 minutes. Median recovery time from 5 mg/L alfaxalone was significantly longer (P < 0.001) in both species, by 5 minutes for black spot barbs and by 17 minutes for peacock cichlids. Variation in induction and recovery times between species was observed, with black spot barbs having significantly (P < 0.0001) faster induction times when treated with both drugs, and a faster recovery time from 5 mg/L alfaxalone.