North Sumatera Fishery Service has exploited 896 hectare potential area
of Toba lake for rearing red tilapia, following such a same business developed by PT Charoen
Pokphand in cooperation with Aqua Farm of Norway. High price of Rp 25,000 per kg live (US$ 2.7) is among the most interesting point. Large demand from United States, Singapore, Japan and several
European countries can be about 7 metric ton per week. Meanwhile local producer only to supply 3 ton per week. The red tilapia used to export
as in fresh fillet or live fish. Red Tilapia has been known having as fast growth rate, much efficient in utilizing feed supplement, pest and
disease resistant, and quick tolerance on any environmental change.
Biology. Red Tilapia first introduced into the country in 1981 by Fresh
Water Fishery Research Station (Balai Penelitian Perikanan Air Tawar = BPPAT). Based on
morphological appearance, the species was much similar with species found in the Philippine. The species was then spread over
the country. The red tilapia convinced as result of crossing between red species Oreochromis mosambicus honorum originated from Singapore and
normal color species Oreochromis niloticus from Japan. The offsprings have varying color as reddish, yellowish and whitish (albino).
Tilapia will have their maturity in 5 -6 months with 400 - 600 grams of body weight. The male can be ditinguished from female on 28 days of
age by it's secondary sexual phenotipic. The male has darken red scales under their chin and stomach meanwhile the female has pale red color.
The female start spawning on 4 months of age (600 grams body weight) along the year for 0.5 to 1.5 months period. They can lay about 400 -
1,000 eggs every spawning which 70 % will hatch as male tilapia. Red tilapia are
polygamy, and it is recommended to have 1 male with 2 female ratio per 10 meter square pond. Oxygen content in range 3 - 5 ppm, pH
vary 6.5 - 8.5, temperature 25 - 28 oC (daily temperature fluctuation below 15 oC), salinity 0 - 15 % are among the ideal constraint of environment condition to support optimum life of red tilapia.
Floating Dragnet Rearing System. Intensive rearing start at fingerling
phase (1 - 1.5 months fry) 25 gram body weight averagely. It is recommended to feed supplement in pellet form which content minimum 25 % protein,
4 - 8 % fat, 10 - 13 % fiber, moisture 13 - 14 %. Feeding two times a day on regular time will customized tilapia to gathering near the surface
at the certain time. Feeding as much as 3 % of the total biomass deter-
mined by random sampling biweekly. Spreading density at 15,000 - 20,000 tilapia per 1,000 square meter pond or 15 - 20 tilapia per square meter
will provide optimum growth rate.
Growth rate and body length are main growing factor in fingerling phase. Growth rate will have sigmoid curve, as slower rate at the initial rear
ing until reaching fingerling size in 2 months. The faster growth will appear until 4 - 5 months of age. In contrary, increment body length
inversely proportional with age. Younger tilapia will grow length faster.
Growing fingerling size red tilapia until reaching market size can be reared in such kinds of location as followed :
1. Static water pond with minimum 100 square meter, 1 meter deep, minimun discharge
water 2 liter per second.
2. Running water pond, with discharge water 20 liter per second.
3. Karamba (basket of dragnet put in stream or lake), with bamboo plait
basin, lake or daM.
4. Fishpond, mainly in rainy season whereas most pond considering lower salinity level
not utilized for rearing marine fish. Spread density would
be 15 tilapia per square
5. Floating dragnet placed in lake and basin. Spread density for 25 - 30 gram of red
tilapia recommended as 50 - 100 tilapia per cubic meter.
As big as 5 x 5 x 2 meter of
floating dragnet can hold for 2,500 - 5,000 tilapia. As this rearing system is much
intensive (500 gram body weight in 4 - 5 months of rearing), feeding should be given
at 4 - 5 times a day as much as 3 % of the total biomass. Total feed given should be
ajusted in accordance with growth pattern of fish for every 15 days.