TALABA OR OYSTER
The country exports oyster to the US, Arabian Peninsula and Japan. In 1985, we sold only 261 kg of fresh and frozen oysters to Okinawa and the Arab states. Exports of preserved oysters to the US reached 2,533 kg in 1985, valued at $6,484. Nevertheless, the local demand is greater than the supply, with fast turnover and heavy trading in the market. Oyster is sold directly to the consumers, processors and exporters.
Oyster farming also promises good returns, ranging from P1.22 to P2.43 per peso invested.
A good source of animal protein, oyster is primary cultivated for good, although it has industrial and ornamental uses. Oyster meat is delicious and is made into special dishes in hotels and restaurants. Oyster shells are used to make orminants, lime paints and poultry grit.
Oyster culture farms in the country range from 1,500 sq m to half a hectare and are usually managed by operator owners. These are found in the coasts of Cavite, Bulacan, La Union, Bataan, Cagayan, Negros and Iloilo. The Bureau of fishery and Aquatic Resources operates several oyster farms all over the country techniques, extend technical assistance to farmers and provide stock to breeders.
Oyster is usually found in shallow waters along the coast. It thrives in sea water with 0.01 to 0.05 per cent saltiness, and can be collected from stones, shells, or any hard object scattered along the coasts. Fertile eggs are released throughout the year with peaks at certain periods. Spats, or larvae that settle on the cling to hard surfaces, appear from late January to early September and also from May to August. They are then found from 30 to 40 cm below the sea level down to the ocean floor.
Species
There are at least 17 species of oysters in the country but only four are cultured commercially. These are the talabang tsinelas (slipper-shaped oyster), the pulid-pulid (palm- rooted oyster) and the kulot or curly oyster. The talabang tsinelas and the kukong kabayo are the two most commonly cultivated species, while the other grow on rocky bottoms coastal zones.
Site Selection
The oyster farm site should not be subject to excessive flooding and should protected from strong current and waves. There should, however, be moderate current for good water exchange. Water should be brackish, unpolluted, and with adequate oyster food such as minutes plants and minerals or any organic particles suspended in the water. Temperature should range from 18 or 28°C and natural predators such as borers, starfishes and crabs should be minimal.
Farming Methods
Productions is best when oyster is cultured above the ocean bottom.
The stake method makes use of bamboo poles to collect and grow the spats. The poles of the tolis are stuck into the soft muddy bottom a meter apart before the spawning or egg-hatching season. The spats settle at the bamboo poles 15 to 120 cm from the lowest tide. The tips of the stakes should extend out to the water surface about a meter high so that pulling the stakes is easy.
The hanging method makes use of hanging collectors or bitin to collect and grow the spats. Each collector is made of five empty oyster shells strung together with nylon rope about a meter long. They are fastened and hung on bamboo plots or rafts at 25 distance from each other. The lower end of the strings should not touch the bottom. To make the lines rigid, attach nuts shells at the end of the lines.
Each bamboo plot usually measures 1 by 20 meters, and there are about 125 plots in half a hectare. To make the plot. three bamboo poles are placed horizontally parallel to each other, spaced half a meter apart. A series of bamboo posts support each plot, staked at one meter intervals. Where the water is deep, the collectors are hung on a bamboo raft.
One roll of nylon rope can make about 180 collectors, while a kaing of empty oyster shells is needed to make 100 bitin or collectors. About 350 collectors are needed to make 100 bitins or collectors. About 350 collectors are ended to plot-43,750 for half hectare farm. Hence, about 2,570 kaings of oyster can be harvested from a half hectare farm, plus 500 additional kaings that can be gathered from the bamboo posts.
Another farming method – the “broadcast” or sabog – is effective only in the shallow water with a depth of about two meters. Oyster shells, stones, gravel and tin cans are thrown in areas where spats abound. These then will serve as settlement materials for the larvae.
Harvest
Oyster are harvested before the spawning period while the meat is still fat, full, rounded, bulging and creamy in appearance or when they reach 4-9 cm after 6 to 12 from the settling of larvae.
With the stakes method, harvesting is done by prying off the cluster of oysters from the poles underwater. Undersized oyster are broadcast and allowed to grow to marketable size so they can command a high price. The bamboo poles can be used for one to two years before being replaced. Average yield per hectare using this method is 4 to 8 tons per year.
For easier harvesting use floating rafts, constructed to fit-in-between rows of stakes or bamboo plots.
With the hanging method, harvesting is done by cutting or untying the hanging collectors from the bamboo poles. Clusters of oysters are separated by knocking them off the rope. Average yield per hectare using this method is 10 to 15 tons per year. Floating rafts produce 40 to 60 tons of oyster per hectare each year.
Postharvest
If oysters are not to be packed or transported immediately, submerge them on raft placed underwater.
Depurate or clean them by submersing in flowing clean sea water for 48 hours. Depression plants or machines may be employed to remove germs and disease causing organisms.
Oysters are sold with or without their shells, or salted into bagoong. For shipping , they are packed in sacks, keep moist, and prevented from sun exposure.
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ALIMANGO OR MUD CRAB
Crab farming has become an integral part of aquaculture in the country. This practice began in the early seventies when some fishpond operators in Bicol, Visayas, and Southern Tagalog started to culture crab as a subsidiary crop in milk fish or bangus ponds.
The crab species Scylla serrata is the biggest and most important member of the family of edible crabs in the Philippines.
Mud crab, or alimango, is considered a delicacy and has become a popular fare in seafood restaurants. It is sought for its very tasty aligue or ripe eggs in the ovary.
Crabs abound in estuaries, mangroves, swamps and tidal waters, living both as a scavenger and a cannibal.
Breeding and Spawning
The mating period of crabs is usually long. When mating, the female is carried by the male, clasping her with three pairs of walking legs. In this condition, it is very easy to catch them. After five days, the female is finally released by the male. Mating usually occurs for four months, during the period May to September. Prior to that, in April, the females develops eggs or aligue.
Crabs spawn in the sea. The newly hatched larvae called zoea are free-swimming. They are carried by the tide to the coast where they migrate to live-in estuaries, swamps and mangroves. Fertility is very high among females. As much as a million eggs can be laid but mortality is also high because of inclement climatic conditions.
Molting
This is an indispensable stage in the life cycle of crabs. During molting, they shed their covering or carapace. This happens when there is an abrupt increases in the size of their body. After shedding the old carapace, the crab is left with a very soft covering. It becomes an easy prey to other animals and survive, the crab buries itself under the mud until the soft shell hardens.
Culture and Cultivation Methods
Small crabs or crab seeds are caught by fishermen in seashores, swamps and other natural habitats. They are gathered and sold to fishponds operators.
Crabs are raised in brackish water fishponds. Crab and can be raised simultaneously. It is, however, not advisable to culture crabs together with prawns or sugpo, because when prawns undergo molting, crabs eat them.
Choosing the Crab Farm
Choosing a site for crab farming is not difficult. First, there should be adequate supply of estuarine water because good and stable salinity is conducive to growth. Smaller ponds are advisable since they are easier to manage. Make sure the soil is clay or clay loam. This kind of soil is capable of retaining water. If possible, the site should be free from floods. The depth of water is also important. Advisable depth is one meter to prevent exposure of cultured crabs and stop them from boring holes through the dikes. For easy harvesting, the site should have good drainage. This also facilities the practice of pond freshening whereby the water is cleansed by letting in fresh seawater. Available of crab seeds in the area is also important. This ensures a steady number of young crabs for rearing and the continued operation of your farm.
Managing the Crab Farm
For crab farming, the ponds are prepared just like any bangus fishpond but the side of the dikes should be very firm to discourage the crabs from burrowing through. Place banatan or bamboo screen along main dikes to prevent escape of crabs. About 2,000 to 4,000 crab seeds, 2 to 5 cm in length and size, would be needed initially. Stock them directly in the rearing ponds. Feeding is not a problem since young crabs feed on algae and decaying organic matter. As they grow, crabs become carnivorous. Supplement their feed with trash fish and leftover food. Their rate of growth is rather slow. It takes five to six months for crabs to grow into marketable sizes.
Application of fertilizer is helpful. This enhanced the growth of natural food like moss in the ponds.
Harvesting
This is done with different kinds of trap like the bamboo cage, lift net, scissors net, fish corrals and gill nets. Crabs are ready for the harvest and marketing when the piece or two reaches up to a kilo. They are sold alive and can stay out of the water even for a week. They should, however, be kept in damp containers and periodic moistening is important. Feed them with trash fish and other kitchen refuse.
Handling
Adult crabs in captivity are tied with dried nipa strings. Both pincers are tied close to the abdominal cavity to prevent crawling. When transported, proper handling is important. Place them in baskets or tiklis to avoid getting trampled or crushed.
BANGRUS/BANGUS OR MILKFISH
Milkfish, Chanos chanos (Forsskal), locally known as "bangus" or "bangos", is the predominant species being cultured in the Philippines . Hundreds of years ago bangus was grown in ponds along coastal areas. That was the beginning of fish fanning. Bangus is a popular table fare among Filipinos. To the biologist, it is an innately sturdy fish, being able to adapt and thrive even in the confined, unnatural environment of the fishpond. This characteristic is not often found in most other fish species.
Milkfish is a traditional culture species, and has been studied for along "' time. But there is still much to be studied about this fish and its culture to understand and gain greater control of factors that favor its growth and production.
Milkfish is the only species in the Family Chanidae and is most closely related to carps and catfishes. Milkfish lives in the warm waters along the continental shelves and around islands in the Indo-Pacific.
The adults are pelagic, schooling, migratory, large (to 1.5 m, 20 kg), and mature sexually in 5 years. Spawning takes place near coral reefs during the warms months of the year, and populations near the equator spawn year-round. The pelagic eggs (1.1-1.2 mm in diameter) and larvae (3.5 mm at hatching)
stay in the plankton for two weeks. The larvae then migrate onshore and are caught by fine-mesh nets operated along sandy beaches and mangrove areas; these "fry" are 10-17 mm long and used as seedstock in grow-out ponds, pens and cages. Juveniles in the wild live in mangrove areas, coastal lagoons, and even go upriver into lakes; they go back to sea when they get too big for the nursery habitat, or when they are about to mature sexually. Juveniles and adults eat a wide variety of relatively soft and small food items, from microbial mats to detritus, epiphytes, zooplankton, and feeds.
stay in the plankton for two weeks. The larvae then migrate onshore and are caught by fine-mesh nets operated along sandy beaches and mangrove areas; these "fry" are 10-17 mm long and used as seedstock in grow-out ponds, pens and cages. Juveniles in the wild live in mangrove areas, coastal lagoons, and even go upriver into lakes; they go back to sea when they get too big for the nursery habitat, or when they are about to mature sexually. Juveniles and adults eat a wide variety of relatively soft and small food items, from microbial mats to detritus, epiphytes, zooplankton, and feeds.
Milkfish farming is a centuries-old industry in Indonesia, the Philippines, and Taiwan. It has been slow to modernize and now faces challenges from competing aquaculture species and the present economic realities. The domestic market is large and the export market may soon expand.
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