Modern shrimp farming, the
production of marine shrimp in impoundments, ponds,
raceways and tanks, got started in the early 1970s,
and, today, Burma has many shrimp farms.
In Burma, shrimp
farms use a one-phase or two-phase production
cycle. With the two-phase cycle, they stock
juvenile shrimp in nursery ponds and then, several
weeks later, transfer them to growout ponds.
With the one-phase cycle, the nursery ponds
are eliminated, and the shrimp are stocked directly
into growout ponds, after having spent a short
period in an acclimation tank . Farms usually
produce two crops a year, although farms within
10 degrees of the equator sometimes get three
crops a year.
Burma's shrimp
farmers rely on wild shrimp for the production
of seedstock. They capture wild postlarvae,
which are stocked into nursery or growout ponds,
or they spawn wild females at a hatchery. Spawning
requires raising young shrimp through several
larval and postlarval stages.
Hatcheries sell
two products: nauplii (tiny, newly hatched,
first stage larvae) for about $0.50 to $2.00
per million and postlarvae (which have passed
through three larval stages) for $2 to $20 per
thousand. Nauplii are sold to specialized hatcheries
which grow them to the postlarval stage. Postlarvae
production costs range from $2 to $10 per thousand.
Whether gravid
(ready-to-spawn) shrimp are captured in the
wild or matured in the hatchery, they invariably
spawn at night, bit with photoperiod manipulation,
they can be induced to spawn at any time. Depending
on a number of variables (temperature, species,
size, wild/captive and number of times previously
spawned), they produce between 50,000 and 1,000,000
eggs.
After one day,
the eggs hatch into nauplii, the first larval
stage. Nauplii, looking more like tiny aquatic
spiders than shrimp, feed on their egg-yoke
reserves for a couple of days. They then metamorphose
into zoeae, the second larval stage, which have
feathery appendages and elongated bodies but
few adult shrimp characteristics. Zoeae feed
on algae and a variety of formulated feeds for
three to five days and then metamorphose into
myses, the third and final larval stage. Myses
have many of the characteristics of adult shrimp,
like segmented bodies, eyestalks and shrimp-like
tails. They feed on algae, formulated feeds
and zooplankton.
This stage lasts
another three or four days, and then the myses
metamorphose into postlarvae. Postlarvae look
like adult shrimp and feed on zooplankton, detritus
and commercial feeds.
Farmers refer
to postlarvae as PLs, and as each day passes,
the stages are numbered PL-1, PL-2, and so on.
When their gills become branched (PL-13 to PL-17),
they can be moved to the farm. From hatching,
it takes about 25 days to produce a PL-15.
The nursery phase
of shrimp farming, when postlarvae are cultured
at high densities in small earthen ponds or
in inclosures within the growout ponds, occurs
between the hatchery and growout phases. Since
hatchery-produced and wild-caught postlarvae
can be stocked directly into growout ponds,
the nursery phase is not always necessary.
Farmers stock
postlarvae in nursery ponds (0.5 to 5.0 hectares)
at densities of 150 to 200 per square meter
and feed a crumbled diet several times a day.
Protein levels in these feeds range from 30
to 45%. The nursery phase should not exceed
25 days.
Once a growout
operation is stocked with postlarval shrimp,
it takes from three to six months to produce
a crop of market-sized shrimp. Temperature has
a lot to do with it. Shrimp like it hot, and
most species prefer, but are not restricted
to, brackish water.
Growout operations
come in all shapes and sizes. Extensive shrimp
farming (low-density) is usually conducted in
Burma, in low-lying impoundments along bays
and tidal rivers. Impoundments range in size
from a few hectares to over a hundred hectares.
When local waters are known to have high densities
of larval shrimp, the farmer opens the gates,
impounds the wild larvae and then grows them
to market size. Fishermen also capture wild
postlarvae and sell them to extensive farmers
for stocking. Overall, however, stocking densities
are quite low, not over 25,000 postlarvae per
hectare. The tides provide a water exchange
rate of from 0 to 5% per day. Shrimp feed on
naturally occurring organisms, which may be
encouraged with organic or chemical fertilizer.
Construction and operating costs are low and
so are yields. Cast-nets and bamboo traps produce
harvests of 50 to 500 kilograms (head-on) per
hectare per year. Production costs range from
$1.00 to $3.00 per kilogram of live shrimp.
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By:
Siam
Canadian Foods Co., Ltd.
9th Floor, Suite 283/44, Home Place Office Building.
283 Thonglor 13, Sukhumvit 55
Kongton Nua, Wattana, Bangkok 10110,
THAILAND
Call us at +66-2-185-3311
Fax: +66-2-185-3317
E-mail: info@siamcanadian.com
