Technologies- El Niño

(Fisheries Sector)

The productivity of the country's extensive brackishwater ponds can be sustained during El Niño months by shifting to nontraditional cultured species more adapted to high salinity and water temperature. The saline-tolerant tilapia crossbred of Oreochromis niloticus and O. mossambicus was found to have survived semi-arid conditions and desert salt water; and are intensively cultured in desert aquifers in Israel (Pruginin et al. 1988). This hybrid is produced by cross-breeding female O. niloticus, a fast-growing tilapia species and male O. mossambicus, a high salinity tolerant species. When properly acclimatized, the hybrid grows best at 32 ppt (parts per thousand ) (Villegas, 1990) and can tolerate salinity up to 35 ppt.

Fishfarmers may opt to mass produce fingerlings of the hybrids or source out fingerlings from accredited hatcheries to support grow-out operations. The expected size of the fish at harvest is 200-
300 g/fish after four months culture.

Requirements for Adoption

a. Minimum

• shallow brackishwater fish pond facilities such as existing ponds with gate structures, seine net, ordinary water pump

• source of freshwater

b. Support System

• hatchery facilities for the source of sex-reversed hybrid tilapia fingerlings

• technology package, technical assistance, and extension services from fishery agency/institution

Advantages

• High salinity tolerance and ability to thrive in shallow pond water makes the hybrid tilapia a suitable alternative species for milkfish during El Niño months.

Limitations

• low production in extreme salinity levels exceeding 35 ppt

• lack of supply of quality fingerlings

• lack of pureline strains of O. niloticus and O. mossambicus for broodstock

Recommendations

• Production of hybrid fingerling and sex reversal

• Stocking

- Stock breeders (average weight of 150 g) at 3 breeders/m² and a male:female ratio of 1:3.

• Pond Preparation

- Prepare the breeding pond at least seven days prior to stocking.

Follow routine procedures: catch all previous fish stocks, drain, eradicate predators/competitors, level off the pond bottom, lime, fertilize (organic manure at 1,000 kg/ha) and regulate water intake.

• Feeding Management

- Feed the breeders with commercial diets containing at least 25% CPC if the amount of natural food is insufficient.

- Give feeds daily at 3% of total fish body weight (BW), divided into two feeding rations (morning and afternoon).

- Reduce the amount of feed to 2.5% BW/day on the second week and 2% BW/day on the third week.

• Fry Collection and Nursery Rearing

- Start collecting fry (10-11 mm size range) 10 days after stocking the breeders and daily (early morning and late afternoon) thereafter with scissor’s net or dip net.

- Stock the fry in 2 m x 1 m x 1 m fine mesh net enclosure (hapa) installed in the nursery pond at a stocking rate of 1000 pcs/m².

- Grade and sort the fry weekly to maintain uniform growth and to minimize cannibalism; reduce the stocking rate to 500 pcs/m² on the second week and then to 250 pcs/m² on the third week.

• Sex Reversal

- Treat the fry with synthetic male hormone to produce all-male hybrids, which grow faster.

- Start the treatment when the fry are one week old; incorporate the hormone (methyltestosterone) in a mash diet containing 35% CP.

- Give the diet daily at the rate of 20-30% BW, divided into four rations.

- Transfer the fingerlings to regular culture ponds freed of predators after 21 days treatment.

Grow Out Culture

• Source of Fingerlings

- Saline-tolerant tilapia fingerlings can be produced by the farmer in his own hatchery or purchased from tilapia hatchery which produces the crossbred.

• Acclimatization

- Acclimatize the fingerlings gradually from freshwater to saline water prior to stocking. Transfer the fingerlings in aerated tanks and adjust the salinity of the water by
1-3 ppt/day until the salinity of the water in the grow-out pond is reached.

- Siphon out the feces and excess feed from the tanks daily to maintain good water quality.

• Stocking

- Select the appropriate stocking rate in the grow-out ponds, depending on the type of management and the target size of the fish at harvest.

- Follow the same fertilization techniques as in lab-lab and plankton production for milkfish

- Supplement the available natural food with farm-made or commercial feeds at feeding rates of 2.5-8% fish BW.

 

Possible Areas of Application

• Brackishwater ponds all over the country.

Dysfunctional Consequences

• If not properly managed, hybrid tilapia culture may lead to the contamination of milkfish stocks in production ponds with left-over tilapia, when milkfish culture is resumed after El Niño.

Sources of Technology

• PCAMRD, Los Banos, Laguna; Aquatic Biosystems, Bay, Laguna;

• Prof. Lourdes Dureza, Brackishwater Aquaculture Center, University of the Philippines Visayas, Miag-ao, Iloilo;

• Dr. Romeo Dieta, BFAR-National Brackishwater Aquaculture Development and Technology Center, Pagbilao, Quezon.

• Mr. Westly Rosario, BFAR-National Integrated Fisheries Research and Technology Center, Bonuan-Binloc, Dagupan City

References

Cornejo, R.G.; Guerero, L.A. Hatchery, nursery and grow-out techniques for hybrid
tilapia in brackishwater ponds. In: Villacorta, L.G.; Dureza L.A. (eds.). Proceedings of the Third National Symposium and Workshop on Tilapia Farming, 1994. - (Book Series No. 18/94).

PCAMRD. Short courses on tilapia fingerlings production and sex reversal, 1990.

Pruginin, Y.; Fishelson, L.; Karen, A. Intensive tilapia farming in brackishwater from an Israeli desert aquifer. In: Pullin, R.S.V.; Bhukaswan, T.; Tonguthai, K.; Maclean, J.L. (eds.). The Second International Symposium on Tilapia in Aquaculture. ICLARM Conference Proceedings. Manila, Philippines: Department of Fisheries, Bangkok, Thailand, and International Center for Living Aquatic Resources Management. 1998. 15,623p.

Villegas, C.L. Growth and survival of Oreochromis niloticus, O. mossambicus and their F hybrids at various salinities. In: The Second Asian Fisheries Forum. Manila, Philippines, Asian Fisheries Society, undated.