The grouper has light yellowish, to grenish to brown body with unequal spots scattered on the head, body, and fins. There are about 40 species of groupers found in tropical waters. Two species, the E. coioides and E.malabricus, are the most preferred for culturing in ponds and cages.
According to the Southeast Asian Fisheries Development Center (SEAFDEC), the estimated income from a hectare of grouper pond is P640,000 a year. The remarkable increase in domestic and export demand of Lapulapu year after year, can make grouper culture boost the country’s fish production.
Culture of grouper in net cages and brackish ponds, however, failed to reach large-scale levels due to shortage of fingerlings and trash fish as feeds. This situation drove SEAFDEC to develop strategies and techniques in making grouper culture produce optimum return and benefits for local farmers.
Culture in net cages
Choosing the site for net cages culture is the foremost consideration. The most suitable sites provide good water quality and adequate water exchange. They should also offer protection from predators, strong winds and waves.
In constructing the floating cages, one can use bamboo poles and polyethylene netting materials at 25-50 mm diameter to build 4-side panels and one bottom panel. Secure the net to the raft structure of bamboo poles using a rope. The stocking density for grouper fry (2.5-7.2 cm) in nursery cages should range from 100-150 per square meter. A 2x2x2 net can hold 400-600 fingerlings. Sort the fingerlings every week and perform stock sampling every 15 days. Hold them in nursery cages until they are about 16 cm, after which transfer to transition nets is necessary. A 5x5x5 transition net can hold 1,100 fishes. Transfer the grouper to the production net after 2-3 months.
Feed the grouper juveniles with chopped trash fish once or twice daily, in the morning or towards the evening. The recommended feeding time is when the tides are slack to minimize feeds swept away by water current.
Culture in brackish water ponds
The pond used for grouper culture is at least 1-2 meter deep. Tilapia fingerlings can serve as food for grouper juveniles. Stock adult tilapia (5,000-10,000/ha) in the pond and allow spawning for one month. The stocking density for grouper fingerlings is 5, 000/ha. Feed grouper juveniles with chopped trash fish twice a day, half of the feed requirement in the morning and the other half in the afternoon.
It is also important to have constant monitoring of water conditions (water depth – 1.0-1.3 meter; water temperature-24-31o C; salinity- 21-41 ppt; and dissolved oxygen- 4.9-9.3 ppm).
Harvest mature groupers (400-600 grams) in the morning using a drag net. Transfer the fish in holding nets for easy sorting and grading.
A farmer can harvest 4,000 pieces of lapu-lapu per hectare and sell them at P200 per kilo. The estimated net profit is P267,930 /ha for the period of eight months.
by Mary Charlotte Fresco. (Source: “Grouper Culture” published by the Southeast Asian Fisheries Development Center (SEAFDEC), Tigbauan, Iloilo); photo courtesy of alibaba.com