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FREEBIES PAGE
EVVEN has not edited anything.
We have done our own research, supported by the Foundation La Salle.
After 2 years of investigation we came up with a revised plan for
a super-intensive shrimp farm without any negative side effect,
an innovative and creative way to gain more and lose less.
Factors Affecting Production
Introduction:
Shrimp farming, the production
of marine shrimp in impoundments,
ponds, raceways and tanks,
got rolling in the early 1970s, and, today, over
fifty countries
export farmed shrimp. In Ecuador and Brazil, the leading
producers
in the Western Hemisphere, export revenues surpass $200 million
a
year. In Thailand, the leader in the Eastern Hemisphere,
they have passed the
billion dollar mark, and probably would
have hit the two billion dollar mark
this year–if prices had
not tanked. India, Indonesia, China, Malaysia,
Taiwan, Bangladesh,
Sri Lanka, The Philippines, Vietnam, Australia and Myanmar
(Burma) have shrimp farms, and there are shrimp farms throughout
Central and
South America. Honduras, Panama, Belize and Mexico
have big industries, while
smaller industries exist in Colombia,
Guatemala, Venezuela, Nicaragua and
Peru.
The shrimp importing nations–the United States, Western Europe
and
Japan–specialize in high-tech "intensive" (more
below) shrimp farming, but,
thus far, their production has
been insignificant. Many countries in the
Middle East have
shrimp farms, with Iran apparently the leading producer in
the region.
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 (more below).
Farms usually produce two crops a year,
although farms within 10 degrees of
the equator sometimes get
3 crops a year. click to print 
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Hatchery
With the
exception the United States and much of Latin America, the world'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 (larvae 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.
The Hatchery Cycle:Whether
gravid (ready-to-spawn) shrimp are captured in the
wild or
matured in the hatchery, they invariably spawn in the dark, so through
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 easier to work with than P. monodon (the most
popular species in the
Eastern Hemisphere), captive breeding
is more common in the west than the
east. Some of the breeding
facilities recirculate the water in the tanks,
creating a closed
system where water quality variables can be controlled and
external factors limited.
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Hatchery Feeds:
Hatcheries utilize a combination of live feeds, such as
microalgae
and brine shrimp nauplii (Artemia), with one or a number of
prepared diets, either purchased commercially or prepared at the
hatchery.
The principal algal species employed are Skeletonema,
Chaetoceros,
Tetraselmis, Chlorella and Isochrysis. Again,
dry formulated feeds are
popular, but they don't work on a
100% replacement basis.
In the April 2000 issue of the Global
Aquaculture Advocate researchers from
Belgium and Ecuador discussed
dry artificial diets for penaeid shrimp
broodstock.
They said:
We recently conducted a survey on the use of commercial
diets in shrimp
hatcheries with maturation facilities. The
survey included 13 hatcheries in
Ecuador, 2 in Mexico, 3 in
the USA, and 1 each in Colombia and Brazil.
Eighty percent of
the hatcheries surveyed used some artificial broodstock
diets.
In 15% of the hatcheries, artificial diets represented more than
25%
of the total feeding regime. Hatcheries used Breed S (INVE
Aquaculture NV,
Belgium), Higashimaru (Higashimaru Co., Japan),
MadMac–MS (Aquafauna
Biomarine, Inc., USA), Nippai (Japan),
Rangen (Rangen, Inc., USA) and Zeigler
(Zeigler Bros., Inc.,
USA). One hatchery had its own diet made by a feed
manufacturer.
The most popular diet was a dry premix because it allowed
mixing
with other nutrients, minced fresh food and medications.
Preliminary
results of our joint research effort were presented last year at
the 5th Ecuadorian Aquaculture Conference in Guayaquil (October
1999). We
found that an experimental dry diet could replace
50% of the fresh food in
hatchery diets without loss of reproductive
output or larval quality. We also
found that Artemia meal (freeze-dried
Artemia biomass) in the diet formulation
improved diet ingestion
rate, ovarian maturation and fecundity.
Artificial dry diets
for shrimp broodstock offer many advantages, but they are
still
not effective in completely replacing fresh foods. A survey of
commercial shrimp maturation facilities indicated that dry maturation
diets
are widely utilized, but they comprise only a minor share
of the total feeding
regime. Information: Roeland Wouters and
Pactrick Sorgeloos, Laboratory of
Aquaculture and Artemia Reference
Center, University of Ghent, Rozier 44,
B-9000, Gent, Belgium;
and Julia Nieto, CENAIM-ESPOL Foundation,
P.O. Box 0901-4519,
Guayaquil, Ecuador. click to print
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Hatchery Trends:
In the Western Hemisphere, hatcheries are usually very large
and may be associated with big farms. They frequently supply nauplii
to
smaller hatcheries in other regions and other countries.
The smaller
hatcheries raise the nauplii to postlarvae, which
are sold to farms for
stocking in nursery or growout ponds.
Many of the large centralized
hatcheries breed shrimp for special
characteristics, like rapid growth and
disease resistance.
In the United States, specific pathogen-free (SPF) seedstock has
demonstrated
great potential. Prior to the arrival of the Taura
virus in 1995, industry
production doubled when the SPF stocks
were introduced. Unfortunately, the
SPF stocks of P. vannamei
were extremely sensitive to Taura, and the U. S.
industry suffered
major losses in 1995. In the Eastern Hemisphere, small and
medium-scale hatcheries continue to produce most of the seedstock.
Worldwide,
the once clear distinction between Japanese/Taiwanese-style
and Galveston-style
hatcheries is increasingly blurred as a
large number of hybrid operations,
borrowing the best from
both, are adapted to local conditions and experience.
The advent
of the backyard hatchery has further blurred the distinction. Success
has not been the exclusive domain of any one style, and it is becoming
more and more obvious
that hatcheries must be adapted to local
conditions.
New Research: On October 4, 2001, Dr. Shea Tuberty,
a crustacean
endocrinologist at the University of West Florida,
USA, posted this item to
The Crust-L List, a mailing list for
crustacean scientists:
"A newly published paper entitled
'Phytoecdysteroids: Biological Aspects' by
Laurence Dinan in
Phytochemistry (V-57, N-3 P-325) may be of particular
interest
if you are looking for the structure/identity of the 200+
phytoecdysteroids
from which crustaceans form their molting hormones."
Information:
Shea R. Tuberty, University of West Florida, Center for
Environmental
Diagnostics and Bioremediation, One Sabine Island Drive, Gulf
Breeze, Florida 32561 USA (phone 850-934-2431, fax 850-934-9201,
email
tuberty.shea@epa.gov
).
New Product: On October 15, 2001, Electronical
Larviculture Newsletter,
reported: Intervet has launched the
world's first commercial multivalent
vaccine against the major
pathogenic Vibrio species in shrimp, including
luminescent
bacteria. The vaccine, NorvaxShrimpVib®, is incorporated into
second stage Artemia nauplii, which are then fed to the juvenile
shrimp.
Field trials performed in Asia and South America have
shown that the vaccine
significantly improves growth and survival.
Information: Intervet
International, Aquatic Animal Health
Division, P.O. Box 31, 5830 AA Boxmeer,
The Netherlands (phone
31-465-587-600, fax 31-485-577-333, email
info@intervet.com
, webpage www.intervet.com).
click to print
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back Nursery
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. Many farms in the Western Hemisphere now
use
acclimation tanks and raceways (more below) instead of
nursery ponds.
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.
Proponents of nurseries argue that they
improve inventory, predator and
competition control; increase
size uniformity at final harvest; better utilize
farm infrastructure;
permit more crops per year; improve risk management;
produce
stronger postlarvae; and decrease feed waste. Because low salinity
levels can be lethal to postlarvae, nurseries also provide
a halfway house
where salinities can be adjusted to pond levels.
The main criticism of nursery systems is that postlarvae suffer
mortalities
when they are transfered to growout ponds. Spontaneous
mortalities also occur
in nursery ponds when animals are held
beyond 25 days.
Acclimation Tanks: In the Western Hemisphere,
acclimation tanks and raceways
are replacing earthen nursery
ponds, mostly because tanks and raceways provide
more flexibility.
Since they're on top of the pond banks, or higher, it's
easier
to transfer seedstock to the ponds. They make it easy to observe
and
evaluate incoming seedstock, which can be fed special diets
to prepare them
for the rigors of pond life. They make great
holding facilities while ponds
are being harvested, or while
a storm passes overhead. They give the
seedstock a chance to
adjust to pond conditions, particularly salinity and
temperature
before stocking. And they don't have to be next to the ponds.
For example, they can be on the hatchery grounds where it's easier
to control
water quality and feeding. Nurseries in greenhouses
find applications in
temperate climates where it is important
to get a jump on the growout season.
The most important consideration
during acclimation is that the water quality
parameters be
changed slowly. Acclimation densities should not exceed 300-500
postlarvae per liter, depending on animal size and duration
of acclimation.
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Growout
Once
a growout operation is stocked with postlarval shrimp, it takes
from
three to six months to produce a crop of market-sized
shrimp. Northern China,
the United States and Northern Mexico
produce one crop per year, semi-tropical
countries produce
two crops per year, while farms closer to the equator have
produced three crops a year, but rarely. 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. They are classified by
stocking densities
(the number of seedstock per hectare) and called
"extensive"
(low stocking density), "semi-intensive" (medium stocking
density), "intensive" (high stocking density) and
"super-intensive" (higest
stocking density). As densities
increase, the farms get smaller, the
technology gets more sophisticated,
capital costs go up and production per
unit of space increases
dramatically.
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Extensive: Extensive
shrimp farming (low-density) is conducted in the tropics,
in
low-lying impoundments along bays and tidal rivers, often in conjunction
with herbivorous fish. Impoundments range in size from a few
hectares to over
a hundred hectares. When local waters are
known to have high densities of
young shrimp, the farmer opens
the gates, impounds the wild shrimp 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. Since it is illegal in many countries
to build new shrimp
farms in tidal and mangrove areas, almost
no new extensive shrimp farms are
being constructed today.
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Semi-Intensive:
Conducted above the high tide line, semi-intensive farming
introduces carefully laid out ponds (2 to 30 hectares), feeding
and pumping.
Pumps exchange from 0% to 25% of the water a day.
With stocking rates ranging
from 100,000 to 300,000 postlarvae
per hectare, there is more competition for
the natural food
in the pond, so farmers augment production with shrimp feeds.
Construction costs range from $10,000 to $35,000 per hectare. Wild
or
hatchery-produced postlarvae are stocked in growout ponds
which are fertilized
(nitrogen, phosphorus and silicate) to
encourage a natural food chain. The
farmer harvests by draining
the pond through a net, or by using a harvest
pump. Yields
range from 500 to 5,000 kilograms (head-on) per hectare per
year, with 2,000 kilograms per hectare per year a much sought after
goal.
Production costs range from $2.00 to $6.00 per kilogram
of live shrimp.
Farmers usually renovate their ponds once a
year. If too many semi-intensive
farms concentrate in a small
area, they can have a negative effect on the
environment.
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Intensive: Intensive
shrimp farming introduces small enclosures (0.1 to 1.5
hectares),
high stocking densities (more than 300,000 postlarvae per hectare),
around-the-clock management, heavy feeding, waste removal and
aeration.
Aeration–the addition of air, or oxygen, to the water–permits
much higher
stocking and feeding levels. The water exchange
rate can be high, 30% per day
and up. Frequently conducted
in small ponds, intensive farming is also
practiced in raceways
and tanks, which may be covered or indoors.
Construction costs
range from $25,000 to $10,000,000 per hectare.
Sophisticated
harvesting techniques and easy pond clean-up after harvest
permit year-round production in tropical climates. Yields of 5,000
to 20,000
kilograms (head-on) per hectare per year are common.
Production costs range
from $4.00 to $8.00 per kilogram of
live shrimp. It's relatively easy to
convert intensive farms
to other species. Intensive farms frequently cause
environmental
problems.
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Super-Intensive:
Super-intensive shrimp farming takes even greater control of
the environment and can produce yields of 20,000 to 100,000 kilograms
per
hectare per year! Thailand has some super-intensive shrimp
farms. A
super-intensive farm in the United States once produced
at the rate of 100,000
kilograms (whole shrimp) per hectare
per year, but it was wiped out by a viral
disease. Belize Aquaculture,
Ltd., perhaps the most advanced shrimp farm in
the world, uses
super-intensive production techniques.
Farming Strategies: Although
almost all of the shrimp farms built in the last
few years
have been semi-intensive and intensive, much of the world's
production still comes from extensive farms. India, Vietnam, Bangladesh,
the
Philippines and Indonesia are good examples of countries
with vast areas of
extensive farms. Ecuador and Honduras have
extensive farms. China pursues
its own brand of semi-intensive
farming in small ponds. Japan, Taiwan and the
United States
concentrate on intensive shrimp farming–and intensive farms
occur in all the major shrimp farming areas of the world. If the
current
experiments with super-intensive shrimp farming become
profitable, the world's
shrimp industries will be changed forever!
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Settling Ponds:
In an article in the August 2000 issue of the Global
Aquaculture
Advocate, Dr. Claude Boyd, water quality expert at Auburn
University,
concluded that settling ponds were the best technology for
treating the effluent from shrimp ponds:
Shrimp farmers may
think settling basins have to be huge, but they're wrong.
Consider
a 500-hectare shrimp farm with 1-meter-deep ponds operated with
an
average daily water exchange of 2%. The daily water exchange
volume would be
100,000 m3, and on a day when 20 hectares of
ponds are completely drained, the
effluent volume would increase
to only 300,000 m3 per day. To provide a
detention time of
eight hours, a 100,000-m3 settling basin would be necessary.
This would require a 1-meter-deep settling basin of 10 hectares
or a
1.5-meter-deep settling basin of 6.67 hectares, representing
only 2% and 1.3%
of the farm area.
Even if settling basins
are constructed in duplicate and with reserve
capacity, they
still would not require more than 4 to 6% of the area of a
large farm. Of course, on a small farm, the proportion of farm area
devoted
to settling would have to be much larger, often 10
to 20% of farm area.
Nevertheless, settling basins seem to
be the only practical means of treating
effluents from small
or large shrimp farms. Information: Claude Boyd, Auburn
University,
Department of Fisheries and Allied Aquacultures, Alabama
Agricultural
Experiment Station, Auburn University, AL 36849 USA (phone
205-826-4786, email ceboyd@acesag.auburn.edu
). click to print
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Mechanized Harvests: In
an article in the August 2000 issue of the Global
Aquaculture
Advocate, Les Hodgson (owner of Marco Sales, a shrimp
importer/processor),
Kieth Gregg (pond manager at Harlinqen Shrimp Farms) and
Robins
McIntosh (former farm manager at Belize Aquaculture) discussed
mechanized shrimp harvests. Some excerpts:
There are several
types of mechanical harvesting systems, including Archimedes
screw systems, reciprocating vacuum/pressure pumps, and recessed
impeller
pumps.The screw system has many advocates because
it's simple and easily repaired on the farm.
It requires only
a small electric motor because it's designed to
elevate shrimp,
not water. Pump harvesters require larger motors to move
water
and shrimp, but the water-moving capability can be a useful tool.
Our
experience has been with recessed impeller pumps, so we
will focus on them.
Recessed impeller pumps create a water current
that lifts the shrimp to a the
de-watering tower without the
impeller blade ever touching the shrimp. These
pumps have been
used for for moving tomatoes, live trout and juvenile shrimp.
Recessed impeller pumps are hydraulically driven by a separate electric,
diesel, or gas-powered motor. The pumps are available in submersible
and
non-submersible designs. The non-submersible design tends
to lose its prime
periodically, which can be problematic during
peak harvest periods, so in
Texas and Belize, we use the submersible
design.
We prefer to discharge shrimp from the de-watering tower
directly into
1-cubic-meter insulated boxes containing an ice
slurry . We prefer boxes
without drainage plugs due to the
danger of unintentional draining, which can
result in spoilage
if the product is stored in boxes for several days.
To minimize
the number of workers needed during harvest, boxes are pre-filled
with about 21 inches (53 cm) of ice slurry. Slush ice is ideal
for this
purpose. Another option is to pass block ice through
a flaking machine and
then add water to create a slurry. If
bacteria are a problem, chlorine can be
added to the ice slurry
at low levels. For the European market, sodium
bisulfite is
added prevent black spots.
Mechanical harvesting systems reduce
labor requirements for pond harvesting by
at least 50%. For
example, Harlingen Shrimp Farms utilizes six people to
harvest
ponds that yield up to 40 tons. This includes a superrvisor, two
workers for the pallet jack, a forklift operator, and two workers
operating
the harvest machine.
Information: Les Hodgson,
Marco Sales, Inc., P.O. Box 4663, Brownsville, TX
78520 (phone
956-541-4821, fax 956-542-0846, email msshrimp@aol.com
and
Kieth Gregg, Harlingen Shrimp Farms, Ltd., Route 3, Box
300K, Centerline Road,
Los Fresnos, TX 78566 USA (956-233-5723,
fax 956-233-9779, email
hsfbayview@compuserve.com
). click to print
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Factors Affecting Production
Feeds: As farms evolve from
low to high stocking densities, the quality of
feed becomes
very important. Most extensive farms (low stocking densities)
don't feed at all; shrimp feed on naturally occurring food organisms
in the
pond. Other extensive farms use small amounts of feed
and fertilizer to
stimulate the natural food chain. On semi-intensive
farms, with many more
shrimp scouring the bottom of the ponds,
most of the feed is consumed by the
shrimp and less is available
to serve as a stimulant to the natural food web.
Therefore,
the quality of the feed is more important because the shrimp get
most of their nutrition from it. On intensive farms, shrimp
depend on
commercial diets for most of their nutrients, so
intensive farms require the
very best feeds.
Ideally, shrimp
in semi-intensive and intensive farms should be fed four or
five times a day, with at least three hours between feedings. High-quality
feeds offer several advantages over lower quality feeds: better
feed
conversion, faster growth, lower mortalities and improved
water quality. In
1997, feed mills around the world produced
approximately one million metric
tons of shrimp feed. All things
considered, including the abysmal state of
shrimp farming statistics,
that figure probably increased to 1.5 million tons
by 2000.
Feeds can represent over 50% of the production costs on intensive
shrimp
farms, and shrimp feed makes a mighty contribution to
the sludge on the bottom
of the pond. Consequently, shrimp
farmers believe better feeds and feeding
strategies could save
them a lot of money. The shrimp's habit of slowly
nibbling
feed particles causes substantial nutrient losses even if the pellets
are of good quality. Increasing the water stability of the
feed beyond a couple
of hours does not help, because leaching
of the nutrients will continue,
even from pellets showing excellent
physical stability. Within an hour,
shrimp feed can lose more
than 20% of its crude protein, about 50% of its carbohydrates
and 85 to 95% of its vitamin content. As much as 77% of the nitrogen
and 86%
of the phosphorus compounds in shrimp feed are wasted.
The waste either
accumulates on the pond bottom, or is discharged
into the environment.
Instead of increasing pellet stability
beyond
a couple of hours, feeds should include attractants
so they are consumed within 20 or 30 minutes.
Because the Asian
shrimp feed market is highly competitive, most feed
manufacturers
produce feeds with excessive nutrient levels to assure that their
products
are well received in the marketplace. Consequently, shrimp feeds
tend
to contain a considerable volume of fishmeal, usually 30
to 35% of the total.
In those countries that produce shrimp extensively–Indonesia,
India, Philippines, Vietnam and Bangladesh–farmers utilize
feeds with lower
protein and fishmeal levels.
Farmers in
the Western Hemisphere depend almost entirely on dry, commercial
feeds, while 50% of those in the Eastern Hemisphere utilize
farm-made feeds
and natural foods, such as trash fish, seafood
by-products and various
mollusks and crustaceans, a practice
which can encourage the spread of disease
and adds to the organic
load in the pond.
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Feeding Trays:
Most shrimp farmers broadcast feeds from the pond bank or from
small boats. Then they lower feeding trays–small (about 1/2 square
meter),
circular or rectangular, mesh-bottomed baskets containing
feed–into the pond
to monitor consumption. In 1992, shrimp
farmers in Peru began using feeding
trays to feed the entire
pond. They distributed the trays around the pond so
that each
one "feeds" an area of approximately 500 to 1,000 square
meters.
Labor cost are high with this technique. At least two
employees are required
for every 10 hectares of ponds. But,
because feed conversion ratios are so
much lower when feeding
trays are used, labor, construction and equipment
costs are
easily covered by reduced feed costs. In addition, feeding trays
offer the following advantages:
• Less pollution
and cleaner pond bottoms
• Reduced stress, fewer disease problems
and faster growth
• An invaluable source of data on what is
going on in the pond
• Early detection of disease
• Controlled
administration of medicated feeds
• Reduced pumping and aeration
costs
• Less pond maintenance between harvests
• Better
harvest estimates
Hand Feeding Versus Mechanical Feeding:
The November/December 1999 issue of
Panorama Acuícola contains
a great article by René Higuera, technical director
of the
Asociación en Participación Atanasia (a shrimp farm in Mexico),
on the
advantages and disadvantages of hand and mechanical
feeding. Most hand
feeding is done from small, in-pond boats,
while mechanical feeding is done
from pickup trucks that cruise
the banks. click to print
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Advantages of Mechanical
Feeding
• The ability
to feed 100 hectares of ponds with only three employees
traditional
feeding from boats requires one person for every four hectares.
• The cost of the mechanical feeder is actually a little less than
the
cost of the two boats and two outboard motors it would
take to service 100
hectares.
• Feeding times and the logistics
of feeding can be optimized with a
mechanical feeder.
•
A pick-up truck can tow the feeder and carry the feed.
• Fuel
costs are 50% lower than they are for hand feeding.
Disadvantages
of Mechanical Feeding
• Farm roads must be in good condition.
• The dimensions of
the pond may affect feeding efficiency. For example,
a mechanical
feeder throws feed about 30 meters, and it lands in a band about
5 meters wide, so the center of a large square pond would not
receive much
feed.
• Wind may restrict feeding to only
one side of the pond.
• Feed may randomly concentrate in certain
areas, causing areas of high
organic loading and water quality
problems.
• During wet periods, roads often become too slippery
for trucks and
mechanical feeders, so the farmer is obligated
to feed from canoes.
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The Advantages of Hand
Feeding
• Feed can
be distributed evenly and efficiently in any size pond
regardless
of location.
• Competition for feed among shrimp is reduced
because the shrimp remain
more distributed throughout the pond
(as verified by feeding trays).
• Wind and rain do not interfere
with hand feeding as much as they do
with mechanical feeding.
Disadvantages of Hand Feeding
• Efficient supervision is required.
• Labor costs are 12% higher
and fuel costs are 50% higher than they are
for mechanical
feeding.
• Biosecurity is more of problem as equipment and personnel
move from one pond to the next.
click to print top
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Conclusion:
Feeding by hand from canoes is less expensive than mechanical
feeding, especially in large, inaccessible ponds where shrimp are
grown to
large sizes. In small ponds where shrimp are grown
for short periods, the
costs are about the same. Information:
René Higuera, Asociación en
Participación Atanasia (phone 64-17-89-97,
fax 64-17-89-93, email
atanasia@infosel.net.mx
); and Salvador Meza García, Editor, Panorama
Acuícola,
Allende #823-24, Plaza el Dorado, C.P. 85000 Cd.
Obregón, Sonora, Mexico
(phone 52-64-14-79-15, fax 52-64-13-87-98,
email panacua@infosel.net.mx
,
webpage http://www.sea-world.com/panoramacuicola
). click to print
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Aeration:
Shrimp farmers use tidal flow and diesel pumps to maintain stable
water quality conditions and to renew the dissolved nutrients
that sustain
healthy algal blooms in their extensive and semi-intensive
ponds. This
process introduces freshly oxygenated water and
helps flush out wastes. To
further increase oxygen levels,
some semi-intensive farms and most intensive
farms use paddlewheel
and aspirating aerators, electrical/mechanical devices
that
add oxygen to the water. They are used at night and early in the
morning
when oxygen levels are at their lowest. Paddlewheels
slap, beat and churn
oxygen into the surface of the water;
aspirators inject an oxygen-rich stream
of water below the
surface. Shrimp flourish in the currents created by the
aerators.
Paddlewheel aerators have many moving parts and a lot of down
time;
aspirators have few moving parts. Producers of paddlewheel
and aspirating
aerators actively compete for the intensive
shrimp farmer's business. Since
the costs are similar, neither
technology has established itself as better
than the other.
Blower-type aerators (low-pressure air), a third technology, deliver
air to
the bottom of the pond through a network of pipes and
tubes. These simple,
non-mechanical systems can be maintained
with unskilled labor. Less popular
than paddlewheels and aspirators,
they find applications in hatcheries and in
deep ponds where
they break up temperature stratification. Low pressure air
has found many applications in the sewage treatment business and
is likely,
over time, to find more applications in shrimp farming.
High initial costs
and the need to remove parts of the system
prior to harvest limit the use of
low pressure air. click
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Disease:
Diseases represent the biggest obstacle to the future of shrimp
farming. Farms and hatcheries have few defenses against rampaging
protozoa,
fungi and bacteria, but it's viral diseases that
pose the greatest threat.
They have caused major crashes in
Taiwan, China, Indonesia, India, Panama,
Honduras and Ecuador.
Currently the Western Hemisphere fights a virus that
arrived
from the east (whitespot), and the Eastern Hemisphere fights a virus
that arrived from the west (Taura). There are no medications
to treat shrimp
viruses, but management techniques have evolved
which lessen their impact.
In Latin America, prior to the arrival
of the whitespot virus in 1999, Taura
Syndrome Virus was the
biggest killer. Shortly after stocking, it can kill
from 40
to 90% of the postlarvae in a shrimp pond. Although Taura may have
been lurking in the background for years, it officially arrived
on the shrimp
farming scene in June 1992, near Guayaquil, Ecuador.
It hit several farms,
and then disappeared until March 1993,
when it returned as a major epidemic,
killing farm-raised shrimp
throughout the Gulf of Guayaquil. Dubbed "Taura
Syndrome"
because it was first reported on farms along the Taura River, an
area about 25 kilometers southeast of Guayaquil, it's also
called "Little Red
Tail" (La Colita Roja) because
the tail fan and body of affected shrimp turn
pale pink. Taura
has spread to every country in the Western Hemisphere with
the exception of Venezuela where hatcheries maintain captive broodstock
and
restrict the introduction of new brood-stock. Belize appears
to have
eradicated Taura in 1995, only to see it re-appear
in 2001. Wild and captive
vannamei appear to be developing
some resistance to Taura.
In the Eastern Hemisphere, whitespot
virus rages on, but in places like
Thailand, management techniques
have brought it under control. Whitespot
usually strikes when
the animals have been in the water for more than sixty
days,
a critical time for the farmer. He's invested a lot of money in
the
crop, but the shrimp are usually too small to harvest.
In 1996, whitespot
even attacked extensive farms in West Bengal,
India, and the Khulna area of
Bangladesh. Now common in both
hemispheres, it's more lethal than Taura,
kills many varieties
of crustaceans and has many vectors (carriers).
Fortunately,
whitespot is easier to exclude from a farm than Taura because
birds and insects don't appear to be carriers.
Viral attacks
in both hemispheres frequently occur after periods of heavy
rain, a stressful time for shrimp, when temperatures, salinities
and water
quality variables fluctuate wildly.
Good water
quality and lower stocking densities appear to be the best defense
against all diseases. When pathogen populations are low, a
shrimp's defenses
are normally capable of preventing disease,
but when stressed by questionable
water quality and high stocking
densities, shrimp fall prey to "shell-loving"
bacteria,
fungi and viruses.
Hatcheries, which maintain concentrated stocks
of live feeds and developing
larvae, are particularly susceptible
to diseases, which can be introduced with
each new batch of
wild broodstock, a known source of pathogens.
Bacteria also
pose a significant threat to the future shrimp farming, as
evidenced by the Philippines where Vibrios have cut production by
more than
50%. In the July 15, 1999, issue of the journal Aquaculture,
researchers in
the United Kingdom discuss some work with Vibrio
vaccines. Here's the
abstract of their study: "Significant
levels of protection were conferred to
Penaeus indicus larvae
for at least 48 hours when either fresh or
freeze-dried Vibrio
harveyi vaccines were administered by immersion, but not
when
administered orally. The degree of protection increased with the
virulence of the pathogen from which the vaccine was made.
Vaccination of
larvae also induced cross-protection against
challenge by other V. harveyi
strains." Information: A.O.
Alabi, Island Scallops, Ltd., 5552 West Island
Highway, Qualicum
Beach, B.C. Canada V9K 2C8 (email islandscallops@bcsupernet.com
);
and D.A. Jones and J.W. Latchford, School of Ocean Sciences,
University of Wales,
Bangor,Menai Bridge LL57 5EY, UnitedKingdom.
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Bird
Predation: Migrating flocks
of birds can land on a shrimp farm and
quickly consume most
of the shrimp. Almost everywhere birds are protected by
law
and efforts to scare them away are usually futile. Noise cannons,
rockets
and scarecrows work for awhile, but the birds soon
learn to ignore them.
Pollution and the Environment: Whenever
large numbers of semi-intensive and
intensive shrimp farms
concentrate on the same river, estuary or bay, their
rich effluents,
primarily shrimp waste products, uneaten feed and dead algae
and bacteria, lower the quality of the surrounding water, overwhelm
the
environment and create conditions which favor shrimp pathogens.
Moderate amounts of effluents from shrimp farms have a beneficial
effect on
the environment, enriching it without overwhelming
it. In some cases shrimp
farm effluent has improved the local
fishery. The mangroves and mangrove
species that surround many
shrimp farms thrive on moderate amounts of
nutrients from shrimp
farms. In turn, the mangroves prevent erosion and
reduce turbidity
by trapping sediments and binding nutrients. Ecuador's
extensive
shrimp farms operate in a comfortable balance with the mangroves.
In some parts of Thailand, Indonesia and the Philippines, where
pollution has
put shrimp farms out of business, mangroves have
reclaimed shrimp ponds. In
Thailand, Venezuela and Ecuador,
shrimp farmers restore and protect mangrove
areas.
back
The
Weather
The weather
plays a major role in the shrimp farmer's life. He never knows
what to expect, but must be ready to alter labor, feeding, pumping,
aeration
and harvesting schedules and then be prepared to operate
his business from a
boat or plane, while waiting for the restoration
of roads, bridges,
electricity and communications. Scheduling
hatchery and farm operations at
these times creates major headaches
for the industry.
In a very general sense, heavy rainfall and
high temperatures benefit shrimp
farming.
The El Niño:
The Monsoon: The southwest monsoon affects the lives of 60% of the
world's
population and has a major controlling effect on world
food production. India
gets 80% of its annual precipitation
from the monsoon, which begins in late
May, when southern trade
winds in the Indian Ocean push moist ocean air
northward toward
southwest India. When they hit the coast in June, they warm,
rise and shed their moisture. The rising air draws in more cool,
moist air,
causing heavy rainfall over most of the country.
The monsoon arrives in Trivandrum, Indian, in June and reaches Bangladesh,
Thailand, China and the Philippines by the end of summer. In
September, when
the orbital position of the tilted Earth changes,
the wind system reverses,
pulling cool, dry air across Asia
and carrying rain to Vietnam, Malaysia,
Thailand, Southeast
India, Sri Lanka, Indonesia and Australia, all of which
farm
shrimp.
Like El Niño in the western hemisphere, the monsoon
flushes out rivers and
estuaries and has a positive effect
on shrimp farming and broodstock supplies.
If the rains flood
the ponds, however, which frequently happens in West
Bengal,
India and Bangladesh—and elsewhere—its effects can be decidedly
negative.
On October 4, 2001, The Indian Meteorological
Department (IMD) said that the
country had a normal monsoon
in 2001. IMD said cumulative rainfall was 92% of
the long period
average, making 2001 the 13th successive normal monsoon year.
IMD said 30 of 35 meteorological subdivisions received normal to
excess
rainfall.
Every now and then, however, the monsoon
fails, and Indian and Southeast Asia
suffer through endless
droughts and baking heat. Agricultural crops fail,
economies
slump and governments change. When the monsoon fails during an El
Niño year, someone always speculates that El Niño did it. Events
in the 1990s
say they are wrong. El Niño was very active throughtout
the 1990s, but there
was not one missed monsoon. Furthermore,
the 1997/98 El Niño (April 1997 to
April 1998), the biggest
in a century, had no detectable effect on the 1997,
1998 and
1999 monsoons.
Cyclones, Typhoons, Hurricanes and Tropical Storms:
Of the major shrimp
farming nations, only Peru, Brazil and
Ecuador in the western hemisphere and
Thailand, Malaysia and
Indonesia in the eastern hemisphere escape powerful
cyclical
storms. These storms are called cyclones in India and Bangladesh,
typhoons in China and the Philippines and hurricanes in the
western
hemisphere. It's the huge amounts of rain and the surge
of water that
precedes these storms that do the most damage,
easily flooding out an entire
shrimp farming region overnight.
The wind also tears buildings and hatcheries
apart. These storms
hit with enough regularity that shrimp farmers beyond the
safe
countries should be prepared to deal with at least one every ten
years,
or so. In addition to the physical punishment, they
drop enough water to
change the pond chemistry, shocking the
shrimp into weakness and often death.
Tropical storms lack
the punch of the cyclical storms, but they have a similar
effect
on water quality.
For a detailed report on Hurricane Mitch's
(1998) effects on shrimp farming in
Nicaragua and Honduras,
visit the Shrimp News webpage at
http://www.shrimpnews.com
click to print
Conclusion
Viral and bacterial diseases in the growout phase of shrimp farming
have
become the industry's biggest problem, but hatcheries
are still the weakest
link in the production cycle. Fluctuations
in the availability of wild
broodstock and competition from
wild seedstock make hatcheries a risky
business. Also, feeding
the various life stages of developing shrimp takes a
major
effort, and hatcheries are plagued with management, disease and
water
quality problems–but they are constantly improving and
constantly increasing
production. Hundreds of researchers in
a dozen countries work on unraveling
the mysteries of hatchery
production, and thousands of hatcherymen in all the
shrimp
farming countries tinker with new techniques, designs and ideas
to improve production.
When hatcheries become more reliable–and
they will–the production of farm-raised shrimp
will take another
leap forward.
World shrimp farming has grown into a multibillion-dollar
giant, creating
hundreds of thousands of jobs and much-needed
foreign exchange in many third
world countries.
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After 2 years of investigation we came up with a revised plan for
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