Immobilization and survival rates at different life stages in Tilapia guineensis exposed to mustard seed powder as anaesthetics agent was evaluated. A total of 450 T.guineemsis comprised of 150 each of  fingerlings (average length 3.87 ± 1.44 cm, average weight 30.03 ± 2.88 g), juveniles (average length 6.45 ± 1.23 cm, average weight 66.44 ± 2.02 g) and adult (average length 13.77(± 2.66 cm, average weight 150.99 ± 9.77 g) were collected from the pond at low down ebb of the creek. The fish were conveyed to the laboratory in six exposed 50 L synthetic basins and allowed to acclimate for 7 days. Fish were exposed to a 0.00 control; 10.00; 20:00; 200 mg/l 30.00 mg/l and 40.00 mg/l anaesthetic arranged from a standard solution of mustard seeds. Three replicates of 10 fish per tank were used for each life stage. Time to reach and recover from various stages of anaesthesia was recorded after exposures. In addition, mortality was also recorded at each stage of life. Several physical and chemical characteristics of water in the investigational containers were assessed. The crush substances of mustard seed was noted to have induced sedation depending on the concentration and size of the treated fish. The time to attain profound sedation reduced with rising concentration at the entire life phases of the fish,  but was prolonged in adults than in fingerlings and juveniles. The faster you reach deep anaesthesia, the longer it takes to fully recover from the effects of the anaesthetics. The association between the time needed to achieve deep sedation and to complete recovery is greatly reliant on on mustard seed powder concentration (P<0.05), with over-all recovery time being contrariwise relational to recovery time. Survival rates of 90.00, 95.00 and 100.00% have been measured in fingerlings, juveniles and adult fish under heavy anaesthetics influence. This study found that mustard seeds can be effectively used as an anaesthetic for T. guineensis at an ideal dosage of 30.00 mg/L.