Thumronk Amornsakun, Wasan Sriwatana, and Ponpanom Promkaew

pp. 671 - 677

Abstract

The sexual maturity of female snake head fish, Channa striatus was studied by determining fecundity and gonadosomatic index (GSI). It was found that the size at sexual maturity of female snake head fish was 26.45±3.07 cm (mean ± SD,
n=10) in total length and 167.4±48.09 g in body weight. The eggs were floating and rounded. The fertilized eggs had a diameter of 588±20.43 µm. The fecundity was 10,279.1±2,527.9 ova/fish and gonadosomatic index (GSI) was 5.07±1.04 %.
Newly hatched larvae of snake head fish were produced by induced spawning using chemical injection (Suprefact
and Motilium). The sexually mature fishes were cultured in a fiber-glass tank (water volume 300 liters) with the ratio of male
and female brooders 1:1. The fertilization rate, hatching out and hatching rate experiments were carried out using 3 15-liter
glass aquaria (water volume 10 liters) each containing 1,000 eggs. It was found that the average fertilization rate was 76.50%,
hatching out occurred of 28 hr 40 min and average hatching rate was 60.26 % at a water temperature of 26.5-29.0°C. 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 for later determination of yolk absorption time. Observation using a microscope revealed that newly
hatched larvae were 3.18±0.11 mm in total length and had yolk sacs of 1,279.71±196.10 µm³
 in volume. The yolk sacs were
completely absorbed within 80 hr after hatching at a water temperature of 26.5-29.0°C. Up until full mouth development (start
of feeding), 2-hourly samplings of twenty newly hatched larvae were taken from an aquarium for observation of the size of
mouth opening. All the larvae had open mouths about 52 hr after hatching (5.48±0.16 mm TL), and measured 324.30±144.60
µm in mouth opening.
The feeding experiments were carried out using a 15-liter glass aquarium (water volume 10 liters) containing 1,000
larvae aged 1.5 days post-hatching (just before the mouth opened). They were fed with Moina at a density of 10 individual/
ml. Twenty larvae were collected at random from the aquarium at 2-hourly intervals, preserved in 10 % buffered formalin, and
then dissected to determine the presence of Moina in the digestive tract. The digestive tracts were fixed at 62 hr of hatching
at water temperatures of 28.0-30.5°C, and measured 334.87±149.78 µm in mouth opening. The average number of Moina in
the digestive tract at the start of feeding was 0.56 individual/larva.