This research was designed to determine the oxygen consumption (OC) rates of hybrid red
tilapia at nine different fish sizes (fs 1-9), ranging from 110 g to 956 g, at five water velocities (wv)
each with three replicates, ranging from 0 to 40 cm∙s-1 using respirometers. A 5X9 factorial experiment,
in randomized complete block design, showed highly significant (p<0.01) effects of both fish size and
water velocity, as well as the interaction between them. The OC rates were highest in the first hour,
then sharply decreased (p<0.05) by the second hour, and remained stable in the third hour. OC was
significantly reduced as fish size increased. Additionally, average OC for all fish sizes was highest at
water velocity of 0 cm∙s-1 and decreased sharply at 10 cm∙s-1. Fish in size groups fs 1-2 had lowest OC
(0.09-0.19 mg∙l-1∙h-1∙100 g-1) at 10-20 cm.s-1, fs 3-4 had lowest OC (0.05-0.11 mg∙l-1∙h-1∙100 g-1) at
10-30 cm∙s-1, while fs 5-9 had lowest OC (0.03 - 0.08 mg∙l-1∙h-1∙100 g-1) at 10-40 cm∙s-1. An estimated
simulation equation of oxygen consumption was best fitted in the power regression: OC = 0.686 –
0.002fs∙wv + 1.732x10-5fs2∙wv + 1.661×10-6fs2∙wv2 - 7.879×10-6fs3 - 3.985×10-8fs∙wv3 + 8.686x10-7wv4,
with R2 = 0.874.
Keywords
Fish size, Hybrid red tilapia, Oxygen consumption rate, Water velocity