The different ways to grow oysters and mussels Item Type article Authors Aldon, Eva T. Download date 24/09/2021 03:50:55 Link to Item http://hdl.handle.net/1834/35137 aquafarm news • oyster and mussel The different ways to grow oysters and mussels By E A ldon Oysters and mussels can be grown in prone to predation by crabs, starfishes 4. Longline method different ways in estuaries, tidal flats, and and shell borers. Bamboo as stake ma­ Four parallel lines of about 20 m long protected coves. terial is costly and does not collect as and 20 cm apart are strung between two much spats as the oysters shells. bamboo or wooden posts. Strings of OYSTER CULTURE In both the broadcast and stake meth­ threaded oysters shells held every 12- ods, spats are left to grow where they 15 cm apart by small plastic or bamboo 1. Broadcast method have settled. At harvests, smaller oys­ tubes are hung on the line. This is a This is the most "primitive" technique ters are left behind to grow until they modified hanging method with a frame­ where oyster spats settle on empty reach marketable size. work of threaded strings of oyster shells, or other media collectors like cultches made of rope or polyethylene stones or gravel scattered on the oyster 3. Hanging method twine. bed. Harvests are done by diving or Strings made of nylon or polyethylene hand-picking at low tides. This method twine with spacers or knots are com­ 5. Lattice-tray method can only be used in very shallow areas monly used. These are usually placed Bamboo splits are woven into a lattice with firm bottom which are generally in intertidal zones, at depths of 1-2.5 and tied with galvanized wire, nylon or exposed at low tides. meters at the lowest tide. These strings polyethylene twine. The splits are are hanged or fastened to bamboo or spaced 15-30 cm apart (1 x 1 x 1 x 2 m). 2. Stake method wooden framework at 25-30 cm apart. The lattice can be positioned like a tray The stake method is usually practiced Variations of this method depend on the horizontally or vertically. They can be in soft, muddy and shallow beds. Bam­ type of collectors used. The most com­ installed in a triangular position sup­ boo stakes are simply stuck in the oys­ mon are as follows: ported by bamboo or wood. Wire mesh ter bed and serve as spat settlement. The trays supported by wooden frames can stakes are aligned and spaced at 0.3-0.6 Empty oyster shells. SRDC (1991) de­ also be used. These are held on wooden meter and are usually as high as the pre­ scribed this method as strings of empty stands or racks which are installed in vailing tide level in the area. shells strung together by a polyethylene tidal flats. Delmendo (1989) reported that this rope (1-3 mm) or monofilament nylon All these methods are applied in in­ method is better than broadcast in that line at 10-15 cm intervals and hung with tertidal zones along shallow coastal ar­ the growth of oysters is faster and mor­ at least 0.5 m clearance from the bot­ eas which become exposed at low tides. tality of spats on settlement to the stakes tom to avoid siltation and bottom pre­ is reduced. However, they are more dation. Sometimes when the spat settlement MUSSEL CULTURE is dense, the strings of cultches are moved farther apart to avoid too much 1. Stake method congestion. Like oyster farming, mussel farming employs the stake method. Bamboo Old rubber tires. These are cut into stakes or mangrove trunk and palm tree halves and tied to the horizontal bam­ trunks are used. As much as 5,000 stakes boo by nylon ropes at 25-30 cm space. could be stuck on a 0.25 ha mussel bed. Or they may be divided into strips of About 2.5-15.0 kg per stake could be 10-20 cm wide and 1.0-1.5 m long at­ produced by this method. tached to the bamboo placed horizon­ A modified stake method called the tally. wigwam is also used. About 7-10 stakes Plastic packaging straps. These 1.5 cm or poles are stuck to the mud bottom in a 2-m radius from a central pole. The Stakes are used to culture oysters width straps are cut into 1.0 m length upper ends of the poles are tied to the and mussels in Ivisan, Capiz. and tied in bundles of 4-5 pieces, be­ west central Philippines tween 20-30 cm intervals. center to form a wigwam. This is used 14 SEAFDEC Asian Aquaculture Vol. XX No. 4 August 1998 aquafarm news • oyster and mussel bigger and heavier. The distance be­ then cleaned to allow new settlement. tween posts is 5 m, and the rope-web is The now big mussels arc grown further stretched 3 m apart along the rows. on nylon net tubes 5 m long and 10 cm Rope-webs are installed parallel with the in diameter. Two net tubes are attached water current and positioned 2 m deep to poles, one above the other. Nets are at low tide. These are untied at harvest wound spirally around the pole. Seed and reused for the next crop. collected from the ropes is transferred to these poles. The ropes cut into 3 m 4. Raft method are wound spirally around a pole. A raft may be made of bamboo with Harvest of marketable mussel (mini­ cross beams buoyed up by empty metal mum. 4 cm shell length) is done in May- or plastic drums, old car tires blown with February by hand, and using a small styrofoam or ferroconcrete bouys. Rafts boat. Mussels are washed, graded, and are installed parallel to the flow of tide. sold. Smaller mussels may be taken hack A unit of raft may be 6 x 8 x 8 x 5 m. to the bouchot. Ropes are hung on the raft, and weighed down to prevent them from floating. 6. Bottom method Collector ropes (for spat) are hung at This is commonly used in the east coast about 0.5 m apart while growout ropes of Scotland along with long-line and raft at 1 m apart. methods. One year old seed mussels (10- Abaca ropes or polycoco ropes are 30 mm) are collected by dredging from used as grow-out ropes. They are pro­ natural beds. These seeds are trans­ vided with bamboo pegs 2 nun long x planted to sheltered inshore waters with Longlines (top) and rafts (bottom) 1.5 cm wide which are inserted into the silty seabed, favorable water currents, may be used for oysters and mussels. lay of the rope at 30 cm interval. These and abundant food. pegs prevent the growing mussels from The mussels remain on culture plots slipping. A 1-meter rope can hold 5-15 (either intertidal or subtidal) for 2.5 to 3 kg of mussels. Grow-out ropes could be years and are harvested by dredging. The in deeper water areas with stronger wa­ as long as 4 m depending on the depth bottom culture method produces 3-5 kg ter movement. The poles serve as spat of the mussel farm. of mussels per m2. collectors but no thinning nor transplan­ tation of spats is made. 5. Bouchot method 7. Long-line method Originated in France, bouchots are gen­ The same principle in oyster culture is 2. Hanging method erally rows of about 125 x 50 m poles at used. The same principle of hanging method 20 cm intervals placed perpendicular to the coastline in the intertidal zone in oyster farming is also used for mus­ REFERENCES sels. However, coconut husks are used (Figueras 1989). Some bouchots are as cultch collectors besides empty oys­ double-rowed at 1 m apart. Delmendo M. 1989. Bivalve Farming: an alter­ ter shells. This method is applied in Spat collection is on the seaward side native economic activity for small-scale coastal fishermen in the SEA region. ASEAN/ deeper water areas as the mussels do not of a bouchot. Growing and fattening mussels is on the landward side. SF/89/Tech. 11. need exposure like the oysters. Figueras AJ. 1989. Mussel culture in Spain and The wooden poles (oak trunk) of a France. World Aquaculture 20 (4) December 3. Rope-web method bouchot are 4 to 6 m long with 3 m in­ 1989. Karayucel S. 1997. Mussel culture in Scotland. A unit of rope-web consists of a paral­ serted into the seabed. Poles to catch mussel seeds are placed from January- World Aquaculture 28 (1) March 1997. lel pair or 5 m ropes at 2 m apart, con­ Nawawi M. 1993. A guide to oyster culture in nected in a zigzag pattern at 40 cm in­ April. Seeds are left on the poles until Malaysia. Bay of Bengal Programme. tervals between knots along each paral­ they reached at least 20 mm. Mussel Seafarming Research Development Center (SRDC). 1991. The science and business of lel rope. Bamboo pegs of 20 cm long seed is not left very long as too much weight can detach whole clusters of growing oysters. SRDC/Philippine Human and 1 cm in width are inserted in each Resource Development Center, Manila. zigzag rope spaced at 40 cm between mussels. pegs. This prevents the mussel clusters Harvest of seed is done in August- from sliding down the rope as they grow December by scraping.