Abstract: Anaesthesia is essential to minimize stress and physical damageduring handling of fish in captivity. In the present study, induction time in Puntius denisonii (Day, 1865), an endangered aquarium fish exposed to four concentrations of MS-222 (50 mg L-1 , 100 mg L , 150 mg L -1 and 200 mg L ) was determined. MS-222 appears to be highly effective as an anaesthetic with no side effects to both fish as well as humans. An induction time of less than or equal to three minutes, and a complete recovery in five minutes was used a basis to record the anaesthesia stages for different doses. The onsets of individual phases of anaesthesia and recovery stages were also studied. Concentration of 150mg L -1 -1 (induction 165±10 seconds and recovery time 112±10 seconds) was determined as the lowest concentration that induces anaesthesia in P. denisonii in less than three minutes. Induction and recovery times were dose-dependent. An inversely proportional relationship was observed between concentrations of anaesthetic and induction time. This is the first study to investigate the efficacy of different concentrations of MS-222 in Puntius denisonii and will be
helpful to develop standardised techniques for transportation, captive breeding and other ex-situ onservation plans for this endangered and endemic barb.
Keywords: Anaesthetic, handling, MS-222, Puntius denisonii, Redlined Torpedo Barb