Grouper, locally known as “lapu-lapu” are among the most commercially important marine food fish in the Philippines and Southeast Asia. They are one of the most expensive fish species and is valued for the excellent texture and flavor of its flesh, as well as its great potential in aquaculture. They are farmed commercially in brackishwater fishpond and net cages. The fish grow fast and attain marketable size of about 500-600 g body weight in 6-8 months of culture depending on the environmental conditions and farm management skills employed.
The grouper industry in the Philippines is developing rapidly mainly due to its export potential. However, its growth and development is constrained by the lack of seeds supply and trash fish feed. The domestic market is primarily the big hotels and seafood restaurants in cities particularly Metro Manila, which pay 3-5 times the normal price for any live grouper weighing between 400-1,000 g body weight.
Commercial Cultured Species
There are about 40 species of groupers distributed in tropical waters but only species are currently popularly cultured commercially.
- Epinephelus coioides – Common name : Orange-spotted, red- spotted, estuary or green grouper)
- Epinephelus malabaricus – Common Name : Black-spotted grouper)
- Epinephelus fuscoguttatus – Common Name : Brown marbled grouper or flowery cod
- Epinephelus amblycephalus – Common Name : Banded or black spotted grouper
- Epinephelus areolotus – Common Name:Areolate grouper
- Epinephilus awoara – Common Name : Yellow grouper
- Epinephilus bleekeri – Common Name : duskytail or yellow spotted grouper
- Epinephelus tauvina – Common Name : greasy or green grouper
- Epinephelus lanceolatus – Common Name : giant grouper)
- Epinephelus akaara – Common name: Hongkong Red spotted or red grouper
- Epinephelus akaara – Common Name : Hongkong, red spotted or red grouper
- Cromileptes altivelis – Common Name : humpback or polka dot gouper
- Epinephelus rivulatus – Common Name : Half-moon grouper
- Plectropomus maculatus – Name : Spotted coral grouper)
Sources of Stock
At present, the supply of grouper fry for commercial cage/pond production still depends on the wild. However, institutes like SEAFDEC/AQD and other progressive finfish hatchery operators are refining their broodstock and seed production techniques. In due time, these hatcheries will be able to supply fry and fingerlings. Grouper fry are collected from tidal rivers, estuaries and coastal bays. Their avaialability is seasonaly although in some areas , grouper juveniles are available all year round, with a peak in November to June.
Tiny groupers measuring 2-3 cm body length abound in estuarine areas particularly near mouth of tidal rivers during spawning season. The fry can be collected by a fish trap net set at the mouth of the river as they are carried by tidal currents toward the shore. Grouper fingerlings measuring 5-12 cm lentth can be caught by baited hook and line, bamboo trap and dip net. They are also gathered in nominal quantities using various devices, e.g. scare-lines or brush piles. In Eastern Visayas, the major sources of grouper fry are in Ormoc City, Guiuan, Eastern Samar and Palompon, Leyte.
The site should :
- Be in calm water, e.g. sheltered lagoons, coves, inlets, bay, behind an island or a river mouth. This is to avoid damage caused by strong winds, waves and currents.
- Have salinity ranging between 20-30 pt for juveniles and 25-35 ppt for adults
- Have a temperature should be between 26-32oC and dissolved oxygen (DO) above 4 ppm
- Have a pH of 7-9 or slightly alkaline and water transparency higher than 3 m
- Have water depth not less than 3 m during lowest low tide
- Have good water exchange to maintain good water quality and ensure effective removal of wastes and adequate supply of dissolved oxygen
- Allow at least 1-2 meter distance between the bottom net cage and the sea bed during the lowest tide water level
- Be relatively free from any source of pollution (industrial, agricultural and domestic) and protected from any environmental hazards such as typhoons, floods, erosions, etc. It must be accessible and preferably secured from vandals and poachers.
Layout-Out Design of Cage Culture
Net cages used for grouper culture can be either floating or fixed type. A floating cage module is usually composed of 4-12 compartments supported by a framework.
- Cage Dimension – The net cages vary in sizes depending on the financial capability of the fish farmer, but the most manageable and economical sizes are 2m x 2m x 1 m, 3m x 3m x 1.5m and 5m x 5m x 2m.
- Cage Shape – Since the shape of net cages does not affect the mobility and growth of the cultured groupers, the square or rectangular shape is mostly preferred than the circular shape because its easier to assemble and managed.
- Cage Frame – Made of bamboo or wooden planks. They must be durable enough to withstand stress caused by wave action and increased weight during culture operation.
- Catwalks – Attach lumber measuring 1 in by 6 in (cross section) and 6 m in length to the framework.
- Sinkers – Use small concrete blocks as sinkers suspended by ropes, placed at the bottom of the 4 corners of the cage or cage module for rigging.
- Floaters – Use plastic drums as floaters on each side of the cage between the bamboo pipes. Tie the drum to the cage frame using a rope 5 mm in diameter to stop the drum from drifting, especially during strong wave action.
- Cage netting – Nets are fabricated like an inverted mosquito net (hapa). Each cage is supported with polyethylene rope (5mm diameter) inserted along the sewed borders of the net and held using a clove hitch with overhand knot. Each cage should have double-layered nets to avoid loss of stock due to tearing and other mechanical damages.
- Anchor – The rope length from the floater to the anchor should be the same as the water depth at high spring tide. The raft structure needs 14 concrete blocks (0.5-1 ton each) with 8 plated at the ebb end ( ebb tide being stronger than flood tide), 4 at the flood end and 2 in the mid-section. Generally, the weight of the anchor should be twice the weight of the
entire floating cage module.
- Shelter – Groupers need a place to hide, unlike other fish. To provide a place for groupers to hide, use sawed-off bamboos, 5 cm in diameter and 15 cm in length (for nursery cages) and 10 cm in diameter and 30 cm in length (for grow-out cages) tied in triangular bundles and suspended in strategic areas inside the net cage.
source: DA – BFAR RF8, Tacloban City