BUHR, Gabriel ; LOWERY, Dr. Sue; DRAWBRIDGE, Mark: The Effect of Current Velocity on Growth and Muscle Development in White Seabass (Atractoscion nobilis)

White seabass (Atractoscion nobilis) are cultured for stock enhancement at the Hubbs -Sea World Research Institute’s marine hatchery located in Carlsbad, California. Historically, current velocities in these systems have been inconsistent and generally low. The purpose of this project was to investigate the effects of current velocity on juvenile white seabass, with the goal of optimizing culture performance. Juvenile white seabass were placed in a recirculating, shallow-water raceway system (183 x 30 x 10 cm deep) and exposed to one of three current velocities. Control fish were reared in tanks with no directional water current. Treatment velocities were expressed as fish body lengths per second (BL/sec), and consisted of slow (0.3 – 0.4 BL/sec), moderate (0.7-0.8 BL/sec) and fast (1.2 – 1.3 BL/sec). Somatic growth, proportions of red and white muscle, and changes in diameter of individual white muscle fibers were measured at intervals of 10 days. White seabass from all treatment groups showed a significant increase in both length and weight when compared to control. The “fast” group exhibited the greatest increase in somatic growth (38% increase in length, 145% in weight), as well as red muscle area (increased by 252%), and the ratio of red to white muscle (increased by 100%) indicating increased aerobic potential. Fish swimming at moderate and slow velocities had thicker white muscle fiber diameters (26% increase in average fiber diameter) when compared to the control groups, indicating a hypertrophy of existing fibers. However, fish swimming at fast velocities had the thinnest muscle fibers of all groups (decrease in average fiber diameter by 13%), suggesting hyperplasia of white muscle fibers.