Presentation on theme: "The Asian sea bass Lates calcarifer - important coastal, estuarine and freshwater fish in the tropical and subtropical Indo-Pacific region It is widely."— Presentation transcript:
The Asian sea bass Lates calcarifer - important coastal, estuarine and freshwater fish in the tropical and subtropical Indo-Pacific region It is widely distributed from the Gulf of Arabia to Northern Australia. Highly Euryhaline with a complex life history Protandrous hermaphrodite and catadromus fish Spawning occurs in brackish waters of 28 to 36 ppt salinity, near river mouths
Spawns from January to August, spawning is triggered by a rise in temperature. spawns usually around full moon and new moon days coinciding with spring tides Highly predacious and cannibalistic, which is the main difficulty in culture of this fish Stringent size grading is required in the culture environments The fish is fast growing and commands good price in local and international markets, hence this is one of the species cultured in Australia, Hong Kong, Singapore, Malaysia and Thailand.
Source of seed Fry - produced in hatcheries Fish - matured in sea cages and bred through environmental manipulation of hormonal injections Wild ripe spawners can also be collected and stripped followed by dry method of fertilization Eggs hatch in hours at a temperature of 29-31°C
They are hatched in seawater of salinity 30 ppt Larvae start feeding from the 2 nd day onwards when they are fed marine rotifer Brachionus plicatilis From day 8 post hatch they are fed with Artemia nauplii or cladocerans days post hatch they are fed with ground trash fish meat/sub-adult and adult Artemia Grading is essential to prevent cannibalism starting from 2 nd weed post hatch.
Grow-out culture In recent years- floating cages Problems –cannibalism and feeding Grow-out - performed in two phases First phase- fry are grown to a weight of about 20 g in special nursery type of ponds of upto 2000m² Stocking rate /m². Besides natural food produced by fertilization, the fry are fed with supplementary feed consisting of ground trash fish twice a day Exchange of 30% per day Reared for 30 – 40 days fingerlings of similar size sorted out and stocked in separate grow out facilities for growing to market size.
Grow-out period - for 3-4 months in Philippines, where g fish are acceptable and 8-2 months in other countries where marketable sized fish is 700g to 1.2 Kg Floating and stationary cages of different sizes (usually 50m²) are used Stocking density in cages is fish /m³, after 3 months stock is thinned out to 10-20/m³ Feed chopped trash fish or pelleted feed specially formulated for Asian sea bass They are 10% of the biomass twice daily for two months after which it is reduced to 5% once a day.
In poly culture fish are reared with forage fish such as tilapias in the ratio of 1:20 The ponds are first stocked with the forage fish which reproduce rapidly and produce fry and fingerlings as food for the sea bass When sufficient food is produced sea bass juveniles are stocked at a rate of 3000 to5000 per ha In monoculture system sea bass juveniles are stocked at 10,000 to per ha with artificial feeding Intensive culture of sea bass has proved to be economical and a production of about tonnes can be obtained The stocked fish in ponds grows to 500g in 6 months; 800 g in one year and to 3 Kg in one and half to two years