EFFECTS OF FLOW VELOCITY ON GROWTH OF JUVENILE COBIA (

Key words: cage aquaculture, cobia, flow velocity, growth,

The objective of this study
was to investigate the growth rate and feed conversion ratio (FCR) of juvenile
cobia, *Rachycentron canadum*, in different flow velocities. In
experiment A, fifteen groups of fish with an initial mean weight of 14.35 g were
reared for 28 days in one of five flow velocities: 0, 5, 10, 15, and 20 cm/s. In
experiment B, fifteen groups of fish with an initial mean weight of 30 g were
reared for 21 days in the same velocities as in experiment A. In experiment C,
fish weighing an average 77 g were raised for 21 days in 0, 10, 20, 30, and 40
cm/s. The optimal velocities in terms of growth rate were 10 cm/s for fish of
10-30 g (experiment A), 20 cm/s for fish of 30-60 g (experiment B), and 23 cm/s
for fish of 60-200 g (experiment C); the optimal velocity increased as the fish
weight increased. FCR and specific growth rate (SGR) also significantly (
p<0.05) corresponded to the flow velocity for the different sized juveniles
with the optimal FCR and weight gains occurring at 10-23 cm/s. FCR rapidly
increased when the velocity exceeded 35 cm/s, regarded as the maximum flow
velocity for fish growth.

* Corresponding author. Tel.: +886-6-926-4115 ext. 1801, fax: + 886-6-9277290, e-mail: slyu@npu.edu.tw