Thumronk Amornsakun, Wasan Sriwatana, and Uraiwan Chamnanwech

pp. 611 - 619

Abstract

Larval sand goby were produced by controlled natural spawning. Fertilized eggs were incubated in
an aquarium tank for hatching. Sampling of the newly-hatched larvae was done at 2-hour intervals, when
20 of them were randomly taken and preserved in 10% buffered formalin solution for later analysis to
determine the time of final yolk absorption. Observation using a microscope revealed that newly hatched
larvae were 2.39±0.12 mm in total length and had yolk sacs of 55.32±14.85 µm³ volume. The yolk sacs
were completely absorbed within 82 hr after hatching at a water temperature of 27.0-30.5 ^oC.
Up until full mouth development (start of feeding), 2-hourly samplings of twenty newly hatched
larvae were taken from the aquarium hatching tank for observation of the size of mouth opening. All
the larvae had open mouths about 36 hr after hatching (2.86±0.97 mm TL), with the mouths measuring
332.29±17.76 µm in mouth height.
The start-of-feeding experiments were carried out using a 15-liter aquarium (water volume 10 liters)
containing 1000 larvae aged 1.5 days post-hatching (just before the mouth opened). They were fed with rotifer at a density of 5-10 ind/ml. Twenty larvae were collected at random from the aquarium at 2-hourly
intervals, preserved in 10% buffered formalin solution, and then dissected to determine the presence of
rotifer in the digestive tract. Digestive tracts fixed 80 hr after hatching at water temperatures of 27.0-30.5 ^oC.,
had mouth height of 549.69±47.94 µm. The average number of rotifer in the digestive tract at the start of
feeding was 0.57 individual/larva.
A starvation experiment was carried out using a 15-liter aquarium (water volume 10 liters) with
three replications. Two hundred newly hatched larvae of sand goby were kept without feeding. Larvae
started to die at 84 hr and totally died within 130 hr after hatching at water temperature ranging from 27.0
to 30.5 ^oC.