Bivalve molluscs or oyster farming have good economic
value, price and job creation. They offer a fish farmer another source of
income. Much like oysters, molluscs is loaded with protein used as ornaments or
in industrial products. Cultivation is possible in communities close to coastal
areas.
Top
Producers
Top producers of molluscs or oyster in the world are
France, Philippines, Spain, USA, Holland and Japan. Philippines uses different
culture methods while Spain and japan specialize in raft culture.
Things
to Consider
Things to consider in Bivalve Molluscs culture are site
selection, breeding stock. Others include moderate tidal currents, site
protection from waves, flooding or strong winds.
More are proper elimination of waste, good distribution
of phytoplankton, oxygen. Make sure the site is free from industrial
pollutants, sewage and test the salinity level, water temperature. A farmer
needs to decide on culture method.
Sewage-Fed-Fish
Bivalve
Molluscs Culture Methods
There are different culture methods to consider. We have
the rack culture, raft culture, bottom, and stake or pole culture.
rack culture
raft culture
bottom
stake
pole culture
Stake
or pole culture
Pole culture are family oriented small business
enterprise. To operate a 15,000 poles harvest the entrepreneur leases sea space
from government. This process guarantees marketable size of 7cm within 17 months
and 5 metric tons on one acre each year.
Pole culture requires the farmer to drive an oak pole to
bottom of sea bed. Choose a pole 20cm, 3m long with ½–2 m exposed above ground.
To minimize predation from sea crabs or starfish wrap bottom 30cm exposed
region with plastic.
Leave 3 m distance between rows and arrange them 1m apart. Then wrap seed mussels around oak poles to
create a mussel bed. Rapid growth of several layers of thick mussels occur
therefor farmer needs to thin the stock.
The smaller specimen are gathered and placed in plastic
net 15cm diameter, 2m long. Wrap the harvested specimens in flexible net tubes
on bare poles to encourage another growth process.
Raft
Culture
Spanish
rafting culture
It takes 12 months for mussels cultivate with this method
to reach 10cm market size. Raft culture uses different materials in the
construct before gathering the mussels. They use Styrofoam, fiberglass, timber.
Others are concrete floats, wooden framework, ropes, water-soluble rayon tube
netting.
The raft is anchored on sides with large concrete mooring
and raft size is 23 x 23 m 9m long with 700 ropes. Then gather natural seed
mussels 7mm from sea bed and place in tube netting. Wrap netting around ropes
while mussel attach themselves to ropes and suspended from raft while net
disintegrates with time.
To harvest lower a large wire mesh basket under the ropes
and hoist them out. Shake to remove mussels remove small sized ones and gather
for transplanting. Japanese farmers use two systems to produce mussels. First
method involves growing oyster seeds in racks placed in shallow waters for 12
months.
Then they are transferred to raft for an additional 12
months. The second method involves gathering then transferring oyster spats
till they attain marketable size. Japanese raft uses tarred wooden floats, Styrofoam
cylinder, hollow concrete drums, and cedar wood poles. Anchor end and tie raft together 10m apart.
The average marketable size of oyster accepted in Japanese market is 8 x 16 cm.
Bottom
and Rack Culture
Bottom culture is a simple way to farm oysters. The
collector scatters different material at bottom of non-shifting, sandy or rocky
waterbed to encourage spatfal to occur. Common material used are different
kinds of hard objects, stones, gravel, cans, and oyster shells.
The main disadvantage of this system includes uncertainty
of yield sustainability to fast underwater currents. Rack culture involves
fixing structures on seabed. They use horizontal poles, rens, strings, trap,
and galvanized wire.
Cost
Considerations
Cost considerations are fixed costs, production costs and
returns. Production costs covers operational costs, depreciation. Fixed costs
involves putting up a shed, dugout, and tools.
Stake and stake preparation include number of bamboo, raft
rental, staking charges, towing charges. Factor production costs like wages of
caretaker, sacks and harvesting charges. Depreciation includes stakes, bolo,
banca, shed.
Fixed
Costs
putting up a shed
dugout
tools
Stake
and stake preparation
number of bamboo
raft rental
staking charges
towing charges
Production
costs
wages of caretaker
sacks and harvesting charges
Depreciation
Stakes
Bolo
Banca
Shed
Returns are based on amount invested, sales of produce,
gross income and net income. Miscellaneous are municipal permit, repairs, total
production cost other expenses.
How to Start Coastal Bivalve Culture
Types of animals in Coastal Bivalve Culture
What type of marine are
grown in Coastal Bivalve Culture. The system accommodates oysters, mussels,
cockles, clams.
Environmental Impact and Challenges
A major challenge is
consumer resistance and some public health risks. Others include rough weather
losses, seed shortage and industrial pollution. More include red tides,
microbial diseases, and high possibility of failure market competition.
Environmental impact are social disruption, export produce market competition.
