Although a scientific breakthrough in 1977, the induced spawning of wild-caught sabalo (adult milkfish) had a low success rate and leads to mortalities. Thus, milkfish were reared to adults in floating net cages (10 m diameter by 3 m deep) and concrete tanks (10 x 10 x 2m or 10 x 25 x 2m deep) supplied with flow-through filtered seawater. Sexual maturation began as the broodstock reached 5 years of age (body weight 3 kgs and above). Since then, natural spawning has been observed annually in floating net cages.
Eggs are immediately collected to prevent cannibalism by the broodstock using a manually operated sweeper-type egg collector. Fine mesh knots attached to an airlift system made of 4Â² diameter PVC pipe collect the eggs in concrete tanks. Egg production of up to 2.5 million/female/season has been attained. Viable eggs are about 80% per spawning, of which 80% hatch. Normal hatchings (straight and without deformities) are usually 80% per spawn.
A diet formulated by SEAFDEC/AQD to support sexual maturation and production of high quality eggs of milkfish is used to feed the broodstock. The diet contains 36% protein (from imported animal and terrestrial proteins), 6% lipid and vitamin mix.
Commercial Fry Production
The water and feeding management schemes for milkfish larviculture have been developed to ensure mass fry production. Hatchery operations utilize either an intensive (high stocking density, high volume tanks, daily feeding and water change) or a semi-intensive (low stocking density, high volume tanks, minimal water change, feeding with mixed diet) system, with an average survival rate of 30% (from stocked newly-hatched larvae). The technology has been used by the private sector to utilize abandoned shrimp hatcheries.
A technique that combines utilizing pre-transport starvation anesthetic at capture, chilled transport water, and a sedating dose of anesthesia effectively transports live broodstock. It was tried on 4-13 year old broodstock placed in oxygenated transport plastic bags (2m long x 0.5 m wide) containing 40-l chilled (20-22Â°C) seawater and 5ml 2-phenoxyethanol (anesthetic). The transport bags were then placed in styrofoam boxes. Travel time was 6-7 hours, recovery was fast, and no mortality was recorded. Eggs (embryonic stage) and newly-hatched larvae were also transported in oxygenated plastic bags containing 12-l seawater and supported by straw bags. Optimum density, temperature, and salinity was 100,000-120,000 eggs or larvae per bag, 28-30Â°C and 32-34 ppt.
To minimize the use of mass-cultured rotifers, a formulated larval diet containing adequate nutrition (highly unsaturated fatty acids and vitamin mix) was found to be an effective supplement for rotifers and alternative for the expensive brine shrimp (Artemia) nauplii for milkfish larviculture.
The Integrated Fish Broodstock and Hatchery Demonstration Complex
Built in 1998, the Integrated Fish Broodstock and Hatchery Demonstration Complex showcases the milkfish breeding and hatchery technologies generated from more than two decades of scientific research. It allows entrepreneurs to obtain first-hand information on the integrated operation of fish breeding and fry production.
A lot 25 x 2 m deep concrete tank fitted with a recirculating system holds milkfish broodstock. An airllift PVC pipe (inset, arrow) fitted with a fine mesh net bag collects eggs naturally spawned by milkfish broodstock. (click image to enlarge)
The Accelerated Transfer of Milkfish Fry Production Technology
As milkfish hatchery technology has been developed on a commercial scale, SEAFDEC/AQD fast-tracked its transfer to the private sector. Shrimp hatcheries, mostly displaced by the decline of the industry, were stocked with milkfish hatchlings through the program on accelerated transfer of milkfish fry production technology. SEAFDEC/AQD provided free milkfish eggs and technical assistance. To date, about 11 private hatcheries have adopted the technology.
A hatchery in Batan, Aklan, previously used for shrimp fry production has been revived for milkfish fry production using SEAFDEC/AQDâ€™s technology
The Grow-Out Culture of Hatchery-Produced Fry
The growth, production, and survival of hatchery-produced milkfish fry were field-tested to compare it with wild-caught fry. The tests consistently showed growth performance of hatchery-produced to be similar with wild-caught fry.
Note: Original article were sourced from SEAFDEC AQD, re-posted on this site with permission.
For more information, contact:
SEAFDEC Aquaculture Department
Tigbauan 5021, Iloilo
Trunkline connecting all offices:
(033) 511-9170 to 71
Email: [email protected]
SEAFDEC Aquaculture Department
Room 102, Ground Floor, Philippine Social Science Center
Commonwealth Ave. corner Central Ave.
1101 Diliman, Quezon City
Tel: (02) 455-0981, 927-5542
Telefax: (02) 927-7825
E-mail: [email protected]