Abstract: The critical swimming speeds and burst swimming speeds were determined in rockfish Sebastes schlegeli and fat greenling Hexagrammos otakii by vertical recirculating water flume and PVC water flume in a laboratory.The effect of swimming on fish body was studied according to the changes in physiological index.The results showed that the rockfish with body length 10-22 cm had critical swimming speed of 44.69-69.07 cm/s,and the relative swimming speed of 3.11-4.69 BL/s.The fat greenling with body length 10-22 cm showed the critical swimming speed of 42.39-82.93 cm/s,and relative swimming speed of 3.45-4.90 BL/s.The rockfish with body length 10-22 cm was found to have burst swimming speed of 76.68-118.18 cm/s.The fat greenling with body length 10-22 cm had burst swimming speed of 81.69-121.25 cm/s.The maximal swimming distance was estimated to be 6 776.4 m in rock fish and 7 423.2 m in fat greenling.According to the results of the burst swimming speed,the most appropriate potential distance for escaping was 15-25 m.After fatigue aroused by critical swimming,the plasma glucose,plasma lactate and muscle lactate concentrations increased significantly in rockfish（P0.05）,no significant differences in muscle glycogen and muscle protein（P0.05）.There were significant increase in the plasma lactic and muscle lactic concentrations and reduction in the plasma glucose,muscle glycogen and muscle albumin in fat greenling（P0.05）.After fatigue aroused by burst swimming,the plasma glucose,plasma lactic and muscle lactic concentrations of increased significantly in rockfish（P0.05）,no significant differences in muscle glycogen（P0.05）.Moreover,the plasma glucose,muscle glycogen and muscle albumin were reduced significantly（P0.05） and increased significantly the plasma lactic and the muscle lactic in fat greenling increased significantly（P0.05）.
2010, Vol. 25 
