Thumronk Amornsakun, Wasan Sriwatana, and Uraiwan Chamnanwech

pp. 373 - 379

Abstract

Time of digestion experiments were carried out in a 15-liter rearing glass aquaria (water volume 10
liters) containing 1,500 larvae. The larvae were fed with sufficient rotifer, Artemia or Moina and then transferred to another rearing glass aquarium without food. Samples of 20 larvae were checked at 10-minute
intervals until no food remained in the larval digestive tract. It was found that the time required to empty
the larval digestive tract with rotifer, Artemia or Moina was as follows. Larvae 3-18 days old fed with rotifer
took 130-180 minutes to empty the digestive tract while larvae 21-27 days old fed with rotifer and Artemia
took 110-120 minutes and larvae 30-45 days old fed with Moina took 80-100 minutes at water temperature
of 25-29ºC. Time consumed to empty the gut content tended to decrease as larval age increased.
Experiments to determined the time and amount of prey required to get satiation were carried out in
a 15-liter rearing glass aquaria (water volume 10 liters) containing 1,500 larvae. The larvae were fed with
rotifer, Artemia or Moina after starvation of 24 hr. Samples of 20 larvae were checked at 10-minutes intervals
after the start of feeding until 3 hr. It was found the time required to fill the larval digestive tract with rotifer, Artemia or Moina for 3-18 days old larvae was 80-110 minutes and amount of rotifer to get satiation was 4.8-
26 ind/larvae. For 21-27 day-old larvae the corresponding time was 60-80 minutes and was 28.5-31.6 ind/
larvae. For 30-45 day-old larvae the time was 40-60 minutes and amount of Moina to get satiation was 34.6-
52.4 ind/larvae at water temperature of 25-29ºC. The time required to fill the larval gut, tends to decrease
with larval age but the amount of prey required to fill the larval gut, tends to increase with larval age.
Experiments to determined the amount of food uptake in a day were done in a 15-liter rearing glass
aquaria (water volume 10 liters) containing 500 larvae, and 10 ind/ml of rotifer, Artemia or Moina. The
amount of food taken was calculated based on changes of rotifer, Artemia or Moina density in the rearing
glass aquarium with and without fish larvae, the 5 samples of each replication were examined at 2 hourly
intervals. The average amounts of rotifer uptake in a day for 3, 6, 9, 12, 15 and 18 day-old larvae were 58.8,
95.4, 64.0, 88.8, 134.0 and 147.4 ind/larvae, respectively. The mean numbers of rotifer added Artemia uptake
in a day by 21, 24 and 27-day old larvae were 181.6, 185.6 and 241 ind/larvae, respectively. And average
amounts of Moina uptake in a day for 30, 33, 36, 39, 42 and 45 day-old larvae were 177.4, 179.4, 214.8, 249.6,
362.8 and 366.2 ind/larvae, respectively.