A salinity stress test was performed using tilapia at late larval stage.
Twelve weeks after placing the parental generation in the broodstock
tanks, about 1000 tilapia larvae were collected from each tank. The
larvae were graded according to size and sixty larvae with a similar
size were selected from each batch for use in the experiment. The average body weight and body length were 18 ± 3 mg and 9.9 ± 0.5 mm,
and 15 ± 2 mg and 9.8 ± 0.8 mm for the larvae from the control tank
and the BFT tank, respectively. The salinity stress test was performed
at 35 g/L NaCl, a concentration that during a preliminary experiment
was determined as the LT50 for the tilapia larvae after 50 min. Six
units of 2 L plastic tanks were filled with 1.5 L of 35 g/L saline water.
The sixty larvae from the BFT broodstock tank and the 60 larvae from
the control tank were distributed into the tanks containing saline
water at a density of 20 fish/tank. After immersion in the saline water
for 60 min, the larvae were transferred to another tank containing freshwater with aeration and 1 h later the number of survivors was determined. The survival of the larvae was also determined 24 h after
transfer into the freshwater tanks.