Effects of egg density, water exchange, and
aeration rate during the egg incubation on embryonic development and
hatching (GRIMC)
The fast experiment on egg density was conducted using
18 transparent tanks, 3 litres volume. Eggs were incubated in six
different densities, i.e. 500, 1500, 2000, 2500, and 3000 eggs/litre, with
three replicates for each treatment. Samples of eggs were taken out from
each tank every hour to observe the embryonic development.
The second experiment on the effect of water exchange
was conducted in 9 transparent tanks, 100 litres volume. Eggs were incubated
at density of 500 eggs/litre, 34 ppt sea water, and with water exchange of 0
% (without water exchange), 100 %, or 200 % water exchange, with three
replicates for each treatment.
The third experiment on the effect of aeration rate
was conducted in 15 transparent tanks, 100 litres volume. Eggs were stocked
at the density of 500 eggs/litre and with 200% water exchange for each tank.
The incubation tanks were equipped with aeration at the different rate, i.e.
without aeration, aeration 350 ml/minute, 550 ml/minute, or 650 ml/
minute, three replicates for each treatment.
The results showed that egg density during the incubation
period did not influence embryonic development. Incubation period was
19-21 hours for all treatments. However, egg density of 500 eggs/litre
resulted in the highest hatching rate (40 %). Water exchange during the
incubation period influenced embryonic development and hatching rate of
eggs. Better (faster) embryonic development was observed with higher water
exchange. Hatching rate was also higher with higher water exchange, i.e.
48.3, 57.6, and 71.6 % for water exchange of 0, 100, and 200 %,
respectively. Aeration rate during the egg incubation did not influence
embryonic development. Eggs hatched after 19 hours incubation period for
all treatments. However, hatching rate was the best (82.3 %) for aeration
rate of 650 ml/minute.
(from Grouper Research Briefs in Aquaculture Asia,
Vol. VI, No. 2, April-June 2001)