FLOW VELOCITY ON GROWTH AND BEHAVIOR IN BLACK ROCKFISH (SEBASTES SCHLEGELII)

In order to investigate the growth and behavior of juvenile black rockfish (Sebastes schlegelii) under different flow velocities, four treatment groups were set up. The average water flows velocity of the four treatments was maintained at 0, 0.5, 1.5, and 2.5 BL/s, expressed as C, L, M, and H, respectively. The experiment lasted for 43d and eight behavior indicators were analyzed. The results showed the following: (1) The final body lengths in M and L were significantly higher than those in the other two treatment groups (P<0.05); the final weight, specific growth rate and weight gain rate were significantly higher in treatment M than those in treatment C and H (P<0.05); the feed conversion ratio was significantly lower in treatment L than that in treatment H (P<0.05). (2) After 30d of the experiment, the accumulated residence time of the outer-circle area was significantly lower in both the M and H treatment groups compared with C and L treatment groups (P<0.05); the accumulated residence time in the middle-circle area was significantly higher in M and L treatment groups (P<0.05); the accumulated residence time of inner-circle area in treatment H was significantly higher than that in other treatment groups (P<0.05); the maximum accelerations of M were significantly higher than those of C and L treatment (P<0.05), after 36d of the experiment, the average velocity of the M treatment was significantly higher than that in the other treatment groups (P<0.05). In conclusion, moderate swimming training significantly improved the growth performance of juvenile black rockfish, and the optimal flow velocity occurred at 1.5 BL/s under the present experimental conditions. Flow velocity significantly influenced the behavioral characteristics of juvenile black rockfish. Behavioral characteristics, such as regional preference and activity status, could be used to assess the respond of juvenile black rockfish to various water flow velocities.