For ponds in the inter-tidal zone, a proper layout should be prepared to include features needed to give the target animals suitable growing conditions with economy in cost of both construction and operation taken into account. Management system envisaged should determine such layout

Extensive, single phase system – The ponds required consists only of grow-outs where fry are stocked, grown to marketable size and then harvested. Main dikes and inlet and outlet gates are the minimum requirements. Where water has to be taken in by pumping, pumps would be required. Semi-intensive, two-phase system would require nurseries, in addition, and pumps as a must. Supply and drainage canals are now incorporated here.

Pond Preparation:

Pond preparation includes draining and exposure of the pond bottom to the air until the bottom cracks and some degree of soil mineralization takes place. All fish and other organisms that might become predators, pests or competitors are eliminated by poisoning with highly degradable pesticides.

Organophosphate insecticides like Gusathion at 0.1 ppm of the product have been used successfully. However, these are to be applied with caution as these are highly toxic to the user.

Snails are very hard to eliminate by merely drying or use of saponin or rotenone but they have been observed to die when the water go beyond 70 ppt salinity. Tri-phenyl-tin compounds which are sold as fungicides have been found to kill snails (Cerithidae) at a concentration of 0.15 ppm but this compound takes very long to degrade.

Where natural food is to be augmented with fertilizers, organic fertilizers or inorganic fertilizers or a combination of both are applied.

In the case of benthic algae, chicken manure is best, followed by pig manure. Although benthic algae are not all of use to the shrimp, small invertebrates that congregate and browse on it becomes valuable food for the shrimp. Filamentous algae and other higher aquatic plants (Ruppia or Chara) also attract these browsing organisms, and are also encouraged, where conditions are not conducive to growing other food but good for these plants.

Application of fertilizers enhances the vegetative growth of these higher aquatic plants, hastens their maturity as well, depending on the type of nutrients applied (nitrogen for growth, phosphorus) for maturation). Detrital algae and Ruppia or Chara are sought more by the small invertebrates.

Culture of benthic algae requires a number of operation and includes 1) drying of the pond bottom to the right hardness, 2) application of organic manure, 3) initial watering, 4) evaporation of the water let in, 5) another drying of the pond bottom, 6) second watering, 7) application of inorganic fertilizer and gradual raising of water depth.

Culture of filamentous algae is undertaken along the following steps: 1) exposure of the pond bottom until the ground starts to crack, 2) seeding with algae or mature Ruppia and/or Chara (where seeds have already formed) 3) filling to shallow depth with water, 4) application of small amount of organic and inorganic fertilizers and 5) nursing the growths while increasing water depth.

Organic fertilizers are cow dung, horse dung and even rice bran.

Chemical fertilizers include single element fertilizers (ammonium sulfate, urea, superphosphate, Triple-superphosphate). Muriate of potash is not necessary. Mixed chemical fertilizers include ammonium phosphate and diammonium phosphate.

In the absence of mixed fertilizers as the above, complete fertilizers (containing N, P and K) are used but with these, K as mentioned before may just be wasted.

Chemical fertilizers are broadcast evenly over the pond. Where benthic algae has become established, even pelleted fertilizers containing phosphorus may be broadcast directly. Ammonium sulfate or urea may be directly applied as these dissolve readily in water. It may be wise to dissolve superphosphate or triple-superphosphate, even pelleted ammonium phosphate and di-ammonium phosphate in water before they are applied. Regular side dressings have been observed to keep the algae growing. Weekly applications with small amounts is preferred. Where water exchange is done during spring tides, fertilizers are applied after the exchange operation is complete. Fertilizer applications are terminated 2 to 4 weeks before the ponds are harvested.

The bottom soil plays a major role in pond yield. High organic matter content in natural soil often promotes higher primary productivity and results a higher production of shrimps. Natural food organisms are one of the most important food sources in shrimp ponds. It is rich in protein, vitamins, minerals and other essential growth elements that simple supplementary feed cannot compete. Fish yield in pond can also be affected by the presence of predators, deteriorating water quality and improper pond management. Hence, pond preparation is the most important step towards higher production.

Shrimp culture operation, may therefore, be grouped into 3 categories:

i.    Those shrimps that depend entirely on naturally produced organisms in the ponds (extensive culture) for their growth,

ii.    Those that depend on both natural food and the application of fertilization the pond water, and sometimes supplementary feeds are also given to enhance the growth rate (improved extensive or semi-intensive culture); and

iii.    Those that depend entirely on artificial feeds and done by intensive management practices i.e. the aeration, draining out water, make water quality upto the standard level etc. (intensive culture).

Pond Drying:

• The drying of the pond bottom is the most practical, easy and effective method of eliminating undesirable species, organisms and materials in grow out ponds prior to the culture operation.
  
• Pond drying process should apply in those areas where there is an available source of water.
  
• Pond should dry the end of the dry season.
  
• Pump machine can be used for drying the pond.
  
• If there is no facility of using pump machine, there will need physical labor.
  
• There is another process of draining system by which pond can also be dried.
  

Water manipulation

Ponds are filled during high tides but with pumps, filling can continue for as long as necessary and if good clean water is available. Water is allowed through screens to ward off entry of predators. Fine screens of 1/16″ mesh are used during the first few weeks and as the shrimp grow bigger, wider mesh filters (1/8″ to 1/4″) take over.

Entry of more water where the finer mesh screens are used could be accomplished by using bag nets instead of the conventional framed screens. The area through which water can pass would depend upon the dimension of the bag net.

In the extensive system, water is allowed as the tide would permit, partially drained just before the onset of the next high tide to be able to take in water again. The more exchange there is, the more probability that additional food has been brought in. Food brought in generally find browsing areas in substrates provided by left-over vegetation or aerial roots of the original mangrove trees or some higher aquatic vegetation which have somehow started to grow.

In semi-intensive systems using fertilizers, water exchange is undertaken as above where conditions have become unfavorable (such as rise in salinity or abrupt lowering of salinity due to heavy rains or low oxygen content etc.) so as to conserve the fertilizers. However, a week after fertilizers are applied at low dosage, partial water exchange during spring tides can be safely done.

Where feeds are used either in supplementary or complete feeding, a regular water exchange routine should be undertaken to get rid of metabolites and provide oxygen expecially where there is high stocking. Systems using entirely formulated feeds or raw animal feeds (trash fish, clam shelle, etc.) would need a flow-through, with water exchange of from 3 to 10% or more per day.

Topography of pond:

Coastal sites where the slopes run gently towards the sea are easier for pond development requiring less financial inputs since excavation cost is minimal.

Filling and draining of water likewise is easily facilitated by gravity. In areas where the above conditions are absent, the use of mechanical pumps are required which again is uneconomic.

In Bangladesh, it has been observed in polders in Satkhira, Khulna, that the surface level inside some of Ghers has become higher than the outside due to heavy sediment deposition and this has caused a failure for further shrimp culture in the area.

Soils of the grow out pond:

The types and texture of the soil of the chosen site should be analyzed before setting on a site for shrimp farming. Soil simples must be taken at random location, preferably upto a depth of 0.5—. I m and subjected to physical and chemical tests to measure the acidity, amount of organic load, level of fertility and physical composition. The soil should have enough clay content to ensure holding water in the ponds. Good quality dikes are usually built from sandy clay or sandy loam materials, which harden, and compacted easily, clay loam or silty clay loam at pond bottom promotes growth of natural food organisms i.e., planktons.

Tilling:

Tilling or ploughing of bottom soil improves soil quality by exposing subsoil to the atmosphere. Thereby speeding up the oxidation process and the release of nutrients are enhanced and are known as an desirable substances that are already locked up in the soil, which is released through ploughing the soil and make them available for primary productivity.

Leaching:

When the pond soil is found to be acidic, it is normally leached. Flushing does this and washing the pond bottom with water to leach away undesirable metallic compounds like aluminium, iron and excess sulphur ions, which cause negative output in shrimp production.

Required water quality of the farm:    

Water quality includes all the inherent physico-chemical and microbiological characteristics of water.

• In a selected site, pH of water preferably ranges from 7.5 to 8.5.
  
• Fluctuations in dissolved oxygen level should be predetermined and the oxygen level should not be lower than 4 ppm.
  
• The water should be turbid but not too turbid. Water with heavy silt load cause clogging of filter nets, sluice gate and increase sedimentation at the pond bottom.
  
• The water should be ideally rich in micro-organisms (both plants and animals).
  

Salinity:

Salinity variation is considered as determinant fact in shrimp production in the coastal farms. Optimum level varies from species to species. For instance, the tiger shrimp (Penaeus rnonodon) grows faster at 15-25 ppt. whereas white shrimp (Penaeus indicus) and (Penaeus merguensis)
tolerate higher salinity ranges (24-40 ppt).

Tidal fluctuation

• Shrimp farming should have moderate tidal fluctuations may range between 2 to 3m. In areas where the tidal range is greater than 4m, this place may prove uneconomical to develop or operate as large and high pond dikes will be required.
  
• In areas where tidal range is less than one meter, water management will be expensive requiring the use of pumps.
  
• The knowledge of tidal range, the highest and lowest water levels, available to farmers, they may build perimeter dike of desired size and height to prevent flooding and even tidal bore of lower magnitudes.
  
• The direction and strength of water current should be known for making provisions for dike construction to reduce erosion.
  
• The proposed site must not be adversely affected by any industrial or agricultural pollution.
  

Liming substances & liming Process:

    The chemicals used for liming of soils are the oxides, hydroxides and silicates of calcium or magnesium since these are the ones capable of reducing acidity. They are given in table below:

Table: Different Types of lime

Doses of liming:    

The doses of liming depend upon the p^H of soil, age of pond and the type of lime. The power of quick lime is two times than lime stone. Before use of lime the p^H of soil of the pond must be examine.

Table: Lime requirement at different p^H levels of soil

Process of use:

• During the pond preparation the solid pieces of lime should make powder in a bag.
  
• For wet method the lime should in a big pan of mud or alluminium pot.
  
• Then the required amount of lime should scatter in the whole pond including the dike equally.
  
• It should be noticed that the whole pond is liming equally.
  

Undesirable species & Predators:

Undesirable species which are pests, competitors and predators consists of fin fishes, crustaceans, molluscs, reptiles, mammals, should be taken care by the shrimp farmers.

Crustaceans

Crabs are one of the worst predators in ponds—causing heavy damage. to the stock. Their dike boring activities are the major causes of water leakage in ponds and sometimes they prey on shrimps.

Amphibians

Frogs are considered as the most common shrimp predator. The adult frogs are harmful when present in sufficient numbers. They also eat shrimps as their majestic
food
sometimes.

Reptiles

Water snakes predate directly on shrimp larvae and adults are therefore extremely harmful when present in sufficient numbers in ponds or nearby areas.

Birds

These are number of wading birds which cause serious problems in shrimp farms such as the king fisher and grey heron. The grey heron
can swallow a whole prey of 15-20 cm in size of Shrimp. These birds are especially harmful when the shrimps concentrate in the surface or other shallow areas providing opportunity for these aerial predators.

. Both interspecies and interspecies competitions prevail
in any shrimp pond, which is also problem.

Control of undesirable species & Predators:

The control of undesirable organism and predator could be done by

1. Physical method
   
2. Chemical method
   

In physical methods

• Drying the pond
  
• Installation of appropriate screens in the out let and in let gates to prevent entrance of undesirable species
  
• Proper maintains of dikes
  
• Netting system: By coetaneous netting it is possible to catch predator and undesirable species by gill net. But through the system it should not be removed properly.
  

By using the chemical methods

eradication of undesirable species is very effective, it becomes less cumbersome, efficient and fast when using chemicals. In selecting chemicals, which have in origin from plant-extracts, compounds are biodegradable and in most cases contribute to the fertility of the pond size.

The commonly used chemicals which are-

Rotenone:

Commercial rotenone available in the markets is in powder from containing 4-5% rotenone. Effective dosage for commercial rotenone is-

        -2g /m³ for eradicating the common predator such as fin fishes and

        -8g/m³ for eel and crabs.

Saponin:

It contains 10-15% saponin widely used to eradicate fin fishes without toxic effect on crustaceans especially shrimp and prawn.

         The effectiveness of saponin decreases with the rate of decreasing salinity. Then the suggested dose is

-12 and 20g/m³ for salinity above 15 ppt.

Calcium carbide:

It is applied to control crabs and pour into the crab hole along with water so that it activates calcium carbide to kill the crab effectively.

Tobacco dust:    

A dosage of 200 kg/ha could be used to kill undesirable predators especially snails and ceephalopods, it also kills mankind.

Amonium sulphate:

it is used as fertilizer and to eradicate undesirable predators while used in combination with lime at dosage to 1 part of amonium sulphate to 5 parts of lime

Removal of aquatic weeds:

Removal of aquatic weeds is essential for successful aquaculture. Because

• It pollutes the water quality.
  
• It creates problem for the movement of the fish.
  
• Decrease the production.
  

Fertilization:

Fertilizer plays an important role for better production. The pond is fertilized to promote and maintain the growth of phytoplankton and zooplankton. Ultimately fertilizing is essential for shrimp culture.

    Two types of fertilizer can be used. These are

        1. Organic fertilizers:

a. Cowdung- 5 Kg/ha/day

                 b. Compost (Green manure)- 5 Kg/ha/day

2. In- organic fertilizers:

a. Urea-5-10 Kg/ha/day

                     b. TSP-5-10 Kg/ha/day        

Identification of post larvae (Fry):

It has been observed that fry collectors sometimes mistakenly identify the postlarvae of Panaeus monodon. However, identification of the postlarvae can be made based on their morphological characteristics such as shape of rostrum, number of rostral teeth, relative length of anternnular flagelle, antennal spine, and presence of dorsal spinules on the 6th abdominal segment.
The chrometophore patterns on the 6th abdominal segment and on the telson and uropods are also useful criteria to identify them.

The identifying points of shrimp are given below:

P. monodon

• A long blackish red or brown line present on the ventral side of the fry.
  
• 14-19 spot found just below the abdomen.
  
• 8 pairs spine found at the edge of the telson.
  
• Spineless on the 6th abdominal segment,
  
• Antennal spine prominently present,
  

M. rosenbergii

• In front of the chephalothorax looks like branches.
  
• At the joined point of abdomine found blue line.
  
• Carapace longer than 6th abdominal segment.
  

• Inner antennular flagellum more than 2 times the outer one, exceeding the latter by 3 distal segments.
  
• Chromatophores are thickly covered on the 6th abdominal segment.
  

Identification of good fry:

We should have select the good fry to decrease the mortality of the fry and also increase the production. Process of identification:

Transportation of shrimp fry:

Fry may be transported in two ways-

1) General methods (In mud pots without oxygen).

2) Modern methods (In polybags with oxygen)

Amount:

3000-6000 fry may be transport in 60×40sq.cm oxygen bag with 6.8 liter water for 12 hours. Without oxygen fry may be transport for 6 hours in the following density and size:

Acclimatization:

It is essential to increase the live rate of fry. After transportation and before stocking the fry we may acclimatize the fry in the flowing ways:

• The pot or bag of fry floats for sometime in the pond.
  
• Exchange of water of the bag or pot and the pond.
  
• After mixing water the temperature and the salinity put in the same range of two water.
  
• Fry can not be released if the water temperature is bellow 20⁰c.
  
• Fry should be released from at 8-9 pm to 8-9 am.
  
• Fry may not be released during raining and strong sunlight.
  

Feed supply:

Feed is essential for better growth and better production. To remove the shortness of natural feed artificial or supplementary feed is essential.

A sample of producing shrimp feed with low cost:

Source: BAFRU

Stocking Time:

The farmer’s stock shrimp in the ghers in the month of Frebuary to March and the stocking is done in the morning or late in the afternoon because shrimp fry are highly sensitive to abrupt changes of water parameters and exposure to sunlight.

Stocking Rate:

Stocking rate varies from area to area. Stocking rate depends on the types of culture system.

    Extensive shrimp culture:         1-2 pcs/m²

    Improve extensive shrimp culture:     3-6 pcs/m²

Semi- intensive shrimp culture:     7-15 pcs/m²

    Intensive shrimp culture:         above 15 pcs/m²

Feeds & Feeding:

In Semi-intensive culture operation, supplementary feeds are given while natural food organisms remain the major food source. In intensive culture operation, shrimp growth is completely dependent on artificial diet

Application of Natural feed in the Pond:

Chicken manure is broadcast at a rate of 600 kg/ha throughout the pond water, then allowed to enter the pond to a depth of 8—10 cm while the pond is further enriched with inorganic fertilizers such as ammonium phosphate (35 kg/ha) and urea (12 kg/ha). Liming the pond alone can produce a luxurious growth of natural food. Application both inorganic and organic fertilizers is useful.

Supplementary feed:

With stocking densities of 3-5 shrimp/rn² and a properly maintained fertilization regime, supplementary feeding is not necessary.

If higher stocking densities are used, distribute supplementary feed as evenly as possible throughout the entire pond.

Table: Percentage of supplementary food by body weight

Formulated feeds successfully used for shrimp have ingredients generally kept secret by the feed manufacturers even if they are required to indicate the formula in tags attached to the bags. Feed technologists and nutritionists, however, have drawn up a number of formulations on the basis of the both experiments and theories.

Artificial feeds are applied late in the afternoon and evenings when the shrimp become active. An intensive system farm in the Philippines feeds its P. monodon stock three times daily: 1700, 2200 and 0700. Feed conversion depends on the feed efficiency and could range from 1.6 for good pelleted feed to 9 for clam meat.Composition of Formula Diet for Penaeid Shrimp, Penaeus merguiensis and Penaeus monodon

Supplement: Cholesterol, 0.5; Soybean lecithin, 3; Corn or soybean oil,
4; Pollack liver oil, 4 Pellet size: 2 × 10 mm; Water: 30%

Diseases of cultured shrimp:

Cultured shrimp have to face different type of diseases. The following shrimp diseases are recognized:

Red-disease:

The red-disease effects on shrimp from juveniles to adult stage and shrimp become reddish.

Blue disease:

The blue disease is created due to nutritional deficiency and shrimp become bluish.

Bacterial disease:

    This only occurs on shell and lastly causes mortality of shrimp.

Fungal disease:

    This may cause 100% mortalities within the period 2 days.

Identification of diseases:

Diseased shrimp is characterized by-

1. Blackening of areas in the exoskeleton.
   
2. Lessions in the walking legs, uropods and carapace.
   
3. Dull whitish coloration of the exoskeleton.
   
4. Sluggish behavior of each individual.
   
5. Soft carapaces are found as usual in sick shrimp.
   
6. Red spot disease is a regular case while intensive is on.
   

At densities of 3-5 pcs/m² diseases should not cause any problem.

Health Management and Remedial Measures:

1. Exchange water.
   
2. Decrease feeding.
   
3. Remove the diseased shrimp from the pond.
   
4. To maintain optimum salinity in the pond.
   
5. To make the environment free of pollution of any type.
   

Harvesting:

    Harvest should start approximately 2 to 3 months after stocking. Harvesting can be done by seine and cast net, by taking advantage of the peak tide during the full and new moon phases. While live shrimps attain an average weight of 30-35 g, the total harvest is done by drying out the pond.

Transporting:    

After harvesting, shrimp should be transported to the processing factory by basket with ice as soon as possible.

Constraints of shrimp culture:

• Lack of establishment of shrimp hatcheries.
  
• Shortage of good quality of shrimp fry.
  
• High price of shrimp or shrimp fry.
  
• Poor sorting, handling, transportation.
  
• Lack of acclimatization during stocking.
  
• Absence of nursery area (mangrove forest).
  
• Poor pond deign and construction.
  
• Competition between alternative land use (agriculture, forestry livestock grazing)
  
• Lack of clear-cut policy regarding shrimp culture.
  
• General lack in use of fertilizer and supplementary feed.
  
• Inefficient harvesting culture technology.
  
• Establishment of processing plant and proper marketing channel.
  

Solution

• Selection of suitable areas for shrimp (Fenaeus monodon) culture and declaring them as shrimp culture are as by the (I.iovemment.
  
• Arrangement for proper supply for drainage of water.
  
• Establishment of shrimp (Penaeus monodon) hatchery in order to ensure the supply of fry
  
• Fragmentation of large plot into suitable size for proper management.
  
• Creation of opportunity for collecting of fry by giving necessary materials to the fry collectors.
  
• Provision I Extension of loan at minimum interest from the commercial bank declaring
  
• The shrimp production as an industry.
  
• Establishment of shrimp (Penaeus mbnodon) feed industries in order to ensure the
  
• Supply of supplementary feed to the growing stock of shrimp. t Development of transport facilities within the culture area.
  
• Development of research facilities and dissemination of the research knowledge to the shrimp producers.
  

Shrimp disease

Shrimp are susceptible to a wide variety of pathogens, including parasites, fungi, protozoa, rickettsiae, bacteria and viruses. Like in any production system, these pathogens cause a considerable loss in production and consequently income. Disease is the phenomenon of the body and its functions when normal physiological activities are disordered by any way. Live animal or that is life to say can he susceptible to the disease. The microorganisms such as bacteria, virus. fungus, parasites and other`s predators and others, all are available in the environment i.e., outer body in which the shrimp remains as a pan of lives. The total organisms remain in a balance condition with their natural biological behavior.

Several diseases have been responsible for mortalities of shrimp in ponds. Black gill disease can be caused by accumulation of debris in gills, usually due to bad bottom conditions.

Fig: Different diseases of shrimp

In the mid 1990.s it was estimated that around 40% of the worldwide shrimp production, representing a value over $3 billion, was lost due to infectious diseases (Lundin, 1996).

The main contributors to these losses are viral diseases. Of the about 20 known shrimp viruses today, six are especially important due to their epizootic spread and economic impact;

► Monodon Baculovirus (MBV),

► Infectious Hypodermal and Hematopoietic Necrosis Virus (IHNNV),

► Taura Syndrome Virus (TSV),

► Yellow Head Disease Virus (YHV),

► Monodon Slow Growth Disease (MSGS) and

► White Spot Syndrome Virus (WSSV).

Of these viruses YHV, TSV and WSSV are notifiable diseases (Office International des Epizooties, Paris, France).

However, the latter of the three, WSSV, is considered the most important disease in terms of spread and economic losses. This virus had, and still has the greatest impact on shrimp culture to date.

The first reports of the virus and its characteristic high mortalities in shrimp farms came in 1992 from the Fuzhan and Quangzhou provinces in China (Nakano et al., 1994). From there the virus spread further into South-east Asia from Japan down to Thailand and Indonesia and later into India and the near East. In 1995 the virus crossed the Pacific Ocean, possibly by transportation of infected post larvae, as the virus was detected in Texas, North America and one year later in South Carolina (Rosenberry, 1996).

Not until 1999 did the virus reach the Latin-American pacific shrimp farming countries where it caused major problems in Ecuador, Peru and Mexico. Fuelled by its sudden appearance and mass mortalities, much research was focused on this at that point unknown virus, resulting in numerous scientific reports describing the virus using several different names such as:

► Systemic ectodermal and mesodermal baculovirus. (SEMBV),

► Rod-shaped virus of Penaeus japonicus. (RV-PJ),

► Penaeid rodshaped DNA virus. (PRDV),

► Hypodermal and hematopoietic necrosis baculovirus. (HHNBV),

►Chinese baculovirus. (CBV) and

►White spot baculovirus. (WSBV).

However, the name .White spot syndrome virus. (WSSV) is nowadays the official name approved by the ICTV (Vlak et al., 2005) and used by the majority of research groups. As the name of the virus already suggests, one of the prominent symptoms of WSSV infections are white spots located on the exoskeleton of the shrimp, especially on the carapace and tail. In earlier stages of infection, the shrimp becomes lethargic, stops feeding and sometimes exhibits a reddish to pink discoloration (Chou et al., 1995). Under farming conditions, infected shrimp surface and approach the edge of the ponds more often than usual and 7-10 days after the initial detection of the disease up to 100% of the shrimp may be moribund or deceased (Lightner, 1996).

Fungus (Fusarium sp.) causes the gills to become black also.

Bacteria can also be responsible. Fungus also causes white shell disease where portions of the exoskeleton turn white. Several vibrio diseases have been reported as also those caused by virus.

It is felt, however, that suceptibility to these epizootic diseases could be due results of stress particularly in systems where stocking rates are very high. Common complaints of shrimp farmers are soft shell, which could be a nutritional disease. Remedial measures have been found for some of these diseases, mainly involving dips in chemical solutions or use of antibiotics but where farming of shrimp is done in ponds, these are not easily applicable.

However, if the environmental conditions that are favorable to shrimp survive change then the shrimp may or may not be weak. The weak shrimp at those situations may be attacked by various microorganisms resulting symptom or syndrome that is actually we refer disease.

Common symptoms of disease in shrimp: The symptoms of syndrome may be behavioral. external and intenal. Note that, the first symptom is from behavioral phenomena of shrimp. The symptoms or symdrome can vary from nature and types of microorganisms in or onto shrimp body.

(a) Behavioral symptoms of diseases in shrimp:The behaviors that differ from healthy shrimp indicate something wrong in the shrimp’s natural activities. The following behavioral phenomena are the sign as symptoms of any diseases:

►Presence of shrimp in feeding tray that is low in number.

►Decrease of rate of feed intake.

►Idleness or continuous resting of shrimp.

►Decrease of rate of movement in water body.

►uncontrolled swimming.

►The jumping phenomenon of shrimp.

►Floating nature in the water shore and outlet.

(b) External symptoms of diseases in shrimp: External features that are the signs of any diseases are mainly the change of color. shape. size and deformation of various appendages. The following external features are commonly considered as symptoms:

►Blackish color or cleft in outer shell or carapace.

►Broom spots or the spots in the joint space of carapace and abdomen.

►Black color in periopods. pleopods and uropods.

►Red color of tail fan.

►Ash and cloudy color of eye-stem.

►white color of eye-lens.

►White spot on shell.

►Pale and hardness of shell.

►Brown color of gill.

►Tearing phenomenon if gills.

►Blending of the body of shrimp. ,

►Rigid body part.

►Finger press signs the notch.

►Downward blending of tail that can not be conducted of expanded.

►Dirtiness of shrimp body.

►Dot spots and swelling of tail part.

(c) Internal symptoms of diseases in shrimp : The internal symptoms are mainly front the color of internal organs, hemorrhage, deformation, presence of microorganism in the tissues of shrimp body. They are highlighted below:

►Change of color or yellow color sign in the hepatupancreas.

►Empty intestine can be observed when dissected.

►Black spots or long black strips are seen in the joint space of muscles and also muscle

in urpods.

►Several white spots can he seen under the shell.

►Many strips of brown color can be observed in the muscles.

Beside these, the features of environment from which various symptoms can be observed. These aregiven below:

►Abruptly death of shrimp in the farm.

►Sudden change of water color.

►Rotten egg like smell around the farm.

►The rapid change of water transparency.

►The rapid change of water salinity.

Types of shrimp disease:

(a)
On the account of the condition of disease, the shrimp diseases can be divided into two categories:

A. Chronic disease and

B. Acute disease

Chronic disease: Long-lasting disease of shrimp from which no instant death occurs. For example poor appetite is a chronic condition. Note that most in cases, environmental diseases are chronic in nature.

Acute disease: Severe disease that causes instant death. Frequently pathogen generated diseases are the acute in nature such as yellow head disease caused by virus.

(B)On the other hand, considering the source of disease, the shrimp diseases can be broadly categorized in two types with which some different sources prevail:

1. Non-pathogenic:
   

►Environmental disease

►Nutritional disease.

(b)Pathogenic:

►Bacteria

►Virus

►Fungus and

►parasites

►Environmental disease of shrimp:

-External Fouling: External Fouling is a syndrome in which the presence of organisms or organic material on the surface of the shrimp interferes with its movement and respiration. The following organisms are most commonly responsible for externalfouling as the result of secondary infection : Protozoa, Algae and Fungi.

Fig: External Fouling

Symptoms;

►Fouling interferes with movement and respiration.

Cause:

►Poor pond bottom.

►High levels of nutrients.

Prevention:

►Fish Solvitrace (commercial name) can be used (Essential Vitamins and Minerals) to prevent / treat chronic soft-shelling, improve molting and induce resistance to disease and anti-stress.

►Fish Stress-C (commercial name) can be used as a vitamin q supplement to boost health/reaction against organic invasions.

►Water quality should have to be improved to encourage molting. water content levels should be checked (ammonium, nitrite, alkalinity, pH) regularly using test kits.

Gill Diseases:

Gill Fouling:

Gill Fouling the shrimp gills, mainly the dead phytoplankton bloom settles The excess organic materials and organisms arc deposited in onto gill filaments when shrimp breaths.

Fig: Gill Fouling

Cause:

►Poor pond bottom.

     ►High levels of nutrients.

Symptoms:

►Fouling interferes with shrimp movement and respiration

Blach Gill :

The black gill disease is the phenomenon of black color of shrimp gills.

Fig: Blach Gill

Causes

►Deposition of melanin in gill tissue.

►Due to low pH.

Pink Gill

►The pink gill disease is the phenomenon of pink color of shrimp gills.

Causes

►Caused by oxygen deprivation.

Fig: Pink Gill

Prevention of gill diseases: