2.2.2. Experiment 2
Due to their performance in experiment 1, diet C and the low water
exchange recirculation system were selected to use for experiment 2.
However, water recirculation rate was adjusted from 280% a day in experiment
1 to 400% a day in experiment 2.
Twenty circular 1-m3 tanks were installed as sand-based recirculation
systems as above. Two salinity regimes were applied to rear
the animals, with 10 tanks at 20–23 g·L−1 and the other 10 tanks at
32–33 g·L−1
. Shrimps were gradually acclimated to the experimental
water salinities over a 10-day period. For each salinity regime, 5 tanks
were allocated for low stocking density at 10 animals per m2 and the
other 5 tanks were allocated for high stocking density at 20 animals
per m2
. Therefore, a 2× 2 factorial experiment in a completely randomized
design involving 4 treatments with 5 tanks as 5 replicates
per treatment was carried out. Treatment 1 was low salinity water
and low stocking density (LSLD); Treatment 2 was low salinity and
high stocking density (LSHD); Treatment 3 was high salinity water
and low stocking density (HSLD); and Treatment 4 was high salinity
water and high stocking density (HSHD). Again as in experiment 1,
domesticated P. monodon juveniles of 1 g in average body weight
were originally reared under water salinity of 32–33 g·L−1 and part
of shrimps were acclimated to water salinity of 20–23 g·L−1
10 days before the experiment. The shrimps then randomly stocked
into the experimental tanks according to salinity treatments and all
feeding and husbandry management followed the protocols described
in experiment 1. The experiment ran for 67 days.