At 6 h, 24 h, 72 h and 168 h after transfer from 30‰ to
treatment tanks, two cages from each treatment tank were
selected randomly for sampling (n=6 fish per treatment at each
time). Three operators each removed a fish from the first cage
using a hand-net and then restrained the fish in a plastic covered
cavity which had been cut in a foam block. Within 2 min of
capture, 0.5–1.0ml of blood was taken from each fish by caudal
puncture using 2 ml syringes and 25 gauge needles. Blood was
transferred fromsyringes to Eppendorf tubes when a sub-sample
of the blood was taken immediately by a 75 mm capillary tube
for estimation of haematocrit (Hct). After blood sampling, each
snapper was placed into an individual aerated 60-l perspex tank
filled with water from the respective treatment tank. Fish from
the second cage were then blood sampled in the same way as
those from the first cage.