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Shrimp Farming - an overview

Shrimp farming, the production of marine shrimp in impoundments, ponds and tanks, got rolling in the early 1970s, and, today, over fifty countries export farmed shrimp. In Ecuador, the leading producer in the western hemisphere, export revenues range from $500 to $800 million a year; in Thailand, the leader in the eastern hemisphere, they have passed the billion dollar mark. In addition, India, Indonesia, China, Malaysia, Taiwan, Bangladesh and Sri Lanka all produce huge amounts of farmed shrimp. The Philippines, Vietnam and Myanmar (Burma) have shrimp farms, and there are shrimp farms throughout Central and South America. Honduras, Panama and Mexico have big industries, while smaller industries exist in Colombia, Venezuela, Nicaragua, Peru, Belize and Brazil. The shrimp importing nations-the United States, Western Europe and Japan-specialize in high-tech "intensive" shrimp farming, but, thus far, their production has been insignificant.

Shrimp farms employ a one or two-phase production cycle. With the two-phase cycle, farms 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 those within 10 degrees of the equator sometimes get 3 crops a year.

 

Hatchery

With the exception of a handful of shrimp farms in the United States and Latin America, the world's shrimp farmers rely on wild shrimp for the production of seedstock. They either 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) and postlarvae (larvae which have passed through three larval stages). Nauplii are sold to specialized hatcheries which grow them to the postlarval stage.

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. 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 reserves for a couple of days. They then metamorphose into zoea, the second larval stage, which have feathery appendages and elongated bodies but few adult shrimp characteristics. Zoea feed on algae for three to five days and then metamorphose into mysis, the third and final larval stage. Mysis have many of the characteristics of adult shrimp, like segmented bodies, eyestalks and shrimp-like tails. They feed on algae, diatoms 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 they molt, the stages are numbered PL-1, PL-2, and so on. When their gills become branched (PL-5 to PL-15), they can be moved to the farm. From hatching, it takes about 20 days to produce a PL-10.

Small-Scale Hatcheries: Hatcheries come in three sizes: small-scale, medium-scale and large-scale. Small-scale hatcheries are usually operated by a family group on a small plot of land. Called "mom-and-pop" or "backyard" hatcheries, they adopt a green-thumb, non-technical approach. Their chief advantages are low construction and operating costs and their ability to open and close, depending on the season and the competition from suppliers of wild seed. They utilize small tanks (less than 10 tons) and concentrate on just one phase of production, like nauplii or postlarvae production. They often use low densities and untreated water. Diseases, the weather and water quality problems often knock them out of production, but they can quickly disinfect and restart operations. Survival of the developing larvae in small-scale hatcheries ranges from zero to over 90%, depending on a wide range of variables, like stocking densities, temperature and the experience of the hatchery operator. Small-scale hatcheries have achieved great success in Southeast Asia, particularly in Thailand, Taiwan, Indonesia, the Philippines and southern China. In Thailand, which has thousands of backyard hatcheries, the industry is segmented into suppliers of nauplii, postlarvae, phytoplankton, equipment, feeds and chemicals.

Medium-Scale Hatcheries: Most medium-scale hatcheries are based on a design developed in Japan and popularized by the Taiwanese. They are called "Japanese/Taiwanese", "eastern" or "green water" hatcheries. They use large tanks, low stocking densities, low water exchange and encourage an ecosystem to bloom within the tank. This bloom feeds the developing shrimp. In some cases, various nutrients and bacteria are added to the tanks which discourage the growth of "bad" bacteria and encourage the growth of "good" bacteria (probiotics). This ecosystem approach is supposed to produce stronger postlarvae due to its closer approximation of natural conditions and the absents of therapeutics. Survival, from stocking to harvested postlarvae, is usually around 50%, or less.

Fig. Larval Rearing Tank

Large-Scale Hatcheries: These are multimillion-dollar, high-tech facilities that produce large quantities of seedstock in a controlled environment. Originally developed at the Galveston Laboratory of the United States National Marine Fisheries Service, they are referred to as "Galveston", "western" or "clear water" hatcheries. Requiring highly paid technicians and scientists, they utilize big tanks (15 to 30 tons), filtered water, high densities, and high rates of water exchange, allowing them to take advantage of the economy of scale by producing seedstock throughout the year. They grow algae and brine shrimp in separate tanks and feed them to the developing shrimp. High survivals, up to 90%, are common with these systems, though in practice survivals range from zero to 70%, on average.

When wild postlarvae are readily available, large-scale hatcheries may also have a difficult time competing with fishermen who supply wild postlarvae to farms. Large-scale hatcheries may have problems with disease and water quality, and they are slow to recover from production failures.

Many large-scale hatcheries maintain captive broodstock in ponds and tanks. The broodstock require expensive live feeds like bloodworms, squid, bivalves and other crustaceans (frozen adult Artemia or krill). Dry formulated feeds are not as popular, since they don't work on a 100% replacement basis.

Since Penaeus vannamei (the most popular species in the western hemisphere) is 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 these breeding facilities recirculate the water in the tanks, creating a closed system where water quality variables can be controlled and external factors limited.

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.

Hatchery Trends: In the western hemisphere, many hatcheries are very large and 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. Large centralized hatcheries open the door to a wide range of possibilities, like genetic manipulation and the development of disease-free stocks.

In the United States, specific pathogen-free (SPF) broodstock 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 industry suffered major losses in 1995. Now an effort is underway in Colombia to develop specific pathogen resistant (SPR) stocks. Initial results have been spectacular, with almost normal survival of 50 to 75% after one or two generations. Similar efforts are underway elsewhere. Mexico claims to have a Taura resistant strain of vannamei, and so does the Oceanic Institute in Hawaii.

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.

Nursery

The nursery phase of shrimp farming, when postlarvae are cultured at high densities in small earthen ponds (and occasionally in intensive raceways or tanks, or in net enclosures within the shrimp ponds), occurs between the hatchery and growout phases. It has some characteristics of the hatchery phase, but more closely resembles growout. Since hatchery-produced and wild-caught postlarvae can be stocked directly into growout ponds, the nursery phase is not always necessary. Consequently, most farms in the western hemisphere are switching from nursery ponds to pond-side acclimation tanks (see below).

Farmers stock postlarvae in nursery ponds (0.5 to 5.0 hectares) at densities of 150 to 200 per square meter. They feed a crumbled diet several times a day. Protein levels in these feeds range from 30 to 45%. In high density raceway nurseries, live brine shrimp larvae are often fed. Most farmers think the nursery phase should not exceed 25 days.

Proponents of nursery ponds 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 provide a halfway house where salinities can slowly be adjusted to pond levels. Covered raceway nurseries find applications in temperate climates where it is important to get a jump on the growout season. The main criticism of nursery systems is that the postlarvae suffer mortalities when they are harvested for stocking into growout ponds. Spontaneous mortalities also occur in nursery ponds when animals are held beyond 25 days.

Acclimation Tanks: In the western hemisphere, especially on farms that don't have their own hatcheries, acclimation tanks and raceways frequently replace nursery ponds. Acclimation facilities give the juvenile shrimp a chance to adjust to pond conditions, particularly salinity and temperature, before being stocked. The holding period lasts from a half day to four days, and the animals may be fed special diets to prepare them for the rigors of pond life. 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.

 

Grow-out

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) and "intensive" (high 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.

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. Extensive farms have little effect on the environment. Since it is illegal in most countries to use tidal or mangrove areas for the construction of shrimp farms, almost no new extensive shrimp farms are being constructed today.

 

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 each 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.

 

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 $250,000 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.
"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. Thus far, super-intensive shrimp farms have achieved only marginal success. Generally, they have problems with management, diseases, crop failures, water quality, finances and the environment. Production levels above 10,000 kilograms per hectare per year are risky.

Fig. Shrimp Culture Pond

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, where most of the farms are semi-intensive, has many 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.

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.

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 processing 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.

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:

o Less pollution and cleaner pond bottoms
o Reduced stress, fewer disease problems and faster growth
o An invaluable source of data on what is going on in the pond
o Early detection of disease
o Controlled administration of medicated feeds
o Reduced pumping and aeration costs
o Less pond maintenance between harvests
o Better harvest estimates

Currently, virtually all the farms in Peru use trays to feed their shrimp, and the practice has spread to Ecuador, Brazil and Central America. At the Fourth Symposium on Aquaculture (Honduras, April 1997), farmers from all over Latin American reported that they were using or investigating the use of feeding trays.

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.

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 caused major crashes in Taiwan (1987-88), China (1993-94), Indonesia (1994-95) and India (1994-96), and significant problems everywhere else, including Ecuador (1993-96) and Honduras (1994-97) in the western hemisphere. Currently the western hemisphere is fighting a virus that arrived from the east, and the eastern hemisphere is fighting a virus that arrived from the west. There are no medications to treat shrimp viruses, but management techniques are evolving which lessen their impact.

In the 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 broodstock. Wild and captive vannamei appear to be developing some resistance to Taura.

Whitespot virus arrived in Latin America in 1999.

In the eastern hemisphere, whitespot virus seems to have no bounds and frequently wipes ponds shortly after stocking. In 1996, it even attacked extensive farms in West Bengal, India, and the Khulna area of Bangladesh. It's more lethal than Taura, kills many varieties of crustaceans and has many vectors (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. More on White Spot Disease

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" vibrio 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. More on diseases

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.

 

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 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, India, 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.

The 1999 monsoon was weak, but normal. On September 1, 1999, Reuters News Service in New Delhi, India, reported: Officials at the Indian Meteorological Department say this season's monsoon rains have so far been "the most deficient" in the last five years. "The rain situation in the state of Andhra Pradesh", one of India's biggest producers of farmed shrimp, "is precarious", said S.M. Virmani, an agro-climatologist at the International Crops Research Institute for the Semi-Arid Tropics.

In the first three months of the June-September monsoon season, rains fell short of normal levels in 36 percent of the country's 424 districts. Meterological officials say some regions face localized droughts. The droughts hit the shrimp farming states on India's southeast coast hard, while some states in the northeast got too much rain.

On September 5, 1999, The Associated Press in New Delhi reported: In normal monsoon years, floods begin to abate by September, but this year, the monsoon has lingered. There's flooding in West Bengal, a state with a large shrimp farming industry.

Andhra Pradesh and Tamil Nadu receive additional rain on the returning northeast monsoon (October through December).

This is the eleventh year in a row that the monsoon has been normal. 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 surge of water that precedes them that does the most damage to shrimp farms. The surge can flood 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.

 
Conclusion

Viral and bacterial diseases in the growout phase of shrimp farming have become the industry's biggest problem.

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.

 
Source: Shrimp News International

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