HATCHING RATE OF YELLOWFIN TUNA Thunnus albacares EGGS UNDER VARIOUS AERATION RATE
Yellowfin tuna broodstock reared in floating net cage spawn in night time. Eggs were directly collected, transported to land-based, selected and treated, then put in incubators. Collected eggs were fertilized but frequently found that hatching rates were varied in larval rearing. Aeration rate was suspected to be the main factor.
The experiment was conducted in 9 fiberglass reinforce plastic (FRP) tanks of 1m3 each. Filled with filtered sea water, aeration system in three rates as treatment, A. 0 mL/s. B. 10 mL/s. and 40 mL/s. and each with three replications. Eggs at heart-beat stage embryo were put into each tank at density of 20 eggs/L.
Hatching rate of eggs were significantly different among treatments A: 27.0 ±0.0 % and B: 27.0 ±0.0 % and C: 40.0 ±0.0 % (f=5.2; df 2,6; p<0.05).
It can be concluded that the best aeration rate for hatching Yellowfin tuna eggs is 40 mL/s with high oxygen supply to support embryonic development as well as to keep eggs disperse in water column as the eggs tend to increase its density toward hatching. On the other hand, the other two treatments failed to supply enough oxygen level to support further embryonic development neither to keep eggs disperse in the water column.