Estuarine crocodile (Crocodylus porosus)

Estuarine crocodile (Crocodylus porosus)










Estuarine crocodile (Crocodylus porosus) is known as the community of the world's largest crocodile. This crocodile differences with other types of scales behind the head is small or absent, dorsal bud scales of short numbered 16 to 17 rows from the front and back are usually 6 to 8 lines. Estuarine crocodile has a size larger than that of freshwater crocodiles in the upper and lower jaw and tooth size. They have a variety of colors from gray to dark green, especially in adult crocodile, while the young crocodile is more greenish color with black spots and stripes on the tail.

Males can grow up to 7 meters (23 feet), but most are less than 5 meters. The female usually has a length of less than 4 meters and can begin to lay eggs and make a nest about 12 years. The maximum lifespan is not known but estimated that they could live at least 70 to 100 years. This type occupies Crocodile estuary habitats, sometimes found in open sea.

Its main food is fish, although it can infect humans and wild boar near the river to drink. This crocodile spread in almost all Indonesian waters.
Estuarine crocodile breeding during the rainy season (months Nov-Mar) and build nests that most of the plants and the soil mound. Nests are usually located in the grass or the edge of the forest along the river or freshwater marsh. In the nest, saved about 50 eggs and incubation lasts between 65 to 110 days-a female crocodile guarding nest is usually closely and therefore these crocodiles hide in the nearest puddle. Incubation temperature determines the sex of crocodile eggs that hatched, at very high temperatures or low temperatures will produce a female crocodile, and the temperature from 31 to 32 degrees Celsius will produce a male alligator. Of eggs - eggs that are stored only about 25%, which will hatch.

source: Warta Pasar Ikan, Dir. PemasarandalamNegeri, DirjenP2HP, DepartemenKelautandanPerikanan

Control and Management of the White Spot Syndrome Virus (WSSV)

By Aqua-In-Tech - Diseases are due interaction between environments, the animal being reared (genetics, health, nutritional status, etc.) and the pathogen. In an ideal system these are in balance with the end result being minimal disease problems and increased profits.

However few, if any, cultural environments are ideal. Constant fluctuations in the environment and the interaction of genetic limitations and viral ecology assure that diseases will be an ever present problem in monoculture rearing environments.

Principles of minimizing the impact of diseases on animal populations are well established in other areas of aquaculture and agriculture. With each year we become able to detect even smaller levels of potential pathogens quicker, causing continual shifts in issues concerning carrier status and minimizing the stress on populations.

What is White Spot?

The term white spot is a description of the characteristic white spot appearance that has accompanied outbreaks of this viral disease around the globe.

• The mere appearance of white spots is not necessarily indicative of the disease that is caused by this virus. Other things can cause white spots.
  
  

• In P. vannamei, though there are white spots, in the disease in the field, they appear late in the infectious cycle and are much smaller than the classic spots noticed in other shrimp species. Classic spots from P. monodon are shown below.

The disease due to the WSSV in P. vannamei is not consistent in its impact. Some areas have been dramatically impacted with total crop failures while others seem to be living with the virus without acute mortality. Only time will tell if this is a permanent pattern. Thailand apparently experienced a similar situation before the problem increased dramatically. It is likely that as the virus spreads and becomes more firmly entrenched in the farm environments that more frequent and severe outbreaks will occur.

What causes the problem?

The disease is associated with a group of viruses that appear to be similar in genetic composition and are widely dispersed geographically. There is some evidence that suggests that not all of the variants are identical though this is the subject of ongoing research. The virus is very large, as viruses go, and has an envelope around it. It is very susceptible to iodine and chloroform and the transmission cycle appears to be easily broken.

Viruses require the host’s metabolic machinery to reproduce themselves and can not be eradicated with antibiotics. However, antibiotics can impact secondary bacterial infections and in theory might be useful if a bacterial infection is stressing animals leading to increased susceptibility.

What is PCR?

PCR is an acronym for Polymerase Chain Reaction. This technique is a valuable tool that enables the detection of minute quantities of DNA. Almost all organisms contain DNA as the primary genetic material, including viruses though some contain RNA. Using a piece of DNA that reacts with the viral DNA it is possible to “fish” for the presence of the virus DNA in a sample. When this piece of DNA reacts with the viral DNA the amount of this reactive DNA is amplified many times over, a billion fold or more. This makes PCR a very sensitive method for detected the DNA of any particular pathogen of interest. While PCR is just coming in to its own as a potential health management tool, it does however have some drawbacks.

• It is technically exacting and prone to occasional errors. False positives (reactions that suggest that you have the virus when you do not) can cause serious problems in that animals that are not carrying the virus can be labeled as carrying it. False negatives are even worse as this can result in keeping stocks that should not be kept.
  
  

• PCR tests need to be validated, sensitive, accurate and reproducible. Not all of the commercially available kits have been this thoroughly tested.
  
  

• PCR does not distinguish between the DNA of a live or a dead virus.
  
  

• PCR is not a quantitative technique. It does not tell you how much viral material there was to start with though it can be interpreted semi-quantitatively.
  
  

• PCR depends upon the sequence of the primers (small pieces of DNA) to react only with the organisms DNA that they have been constructed against. This high degree of specificity is a strength of the assay. Though the primer will react with isolates that are not as virulent as are others or are avirulent.
  
  

• When one is told that a population has been screened (say 150 animals out of a million) by PCR and all have come back negative, this does not mean that none of the animals in the population are carrying the virus. No technique is 100% unless every animal is screened and the technique is 100% accurate.

When sampling animals for the presence of a given pathogen, a specific number of animals are selected at random from the population for further examination. These numbers are based on well establish guidelines in fish health monitoring and certification. Supposedly at 150 out of 1,000,000 animals, you have a 98% chance of finding something that is there. Even if this were true, in a population of one million animals, you could still have 20,000 animals that were carriers. Since random sampling is not usually the case and the analytical techniques are not 100% effective at detecting the pathogen of interest this number could actually be much higher.

Do not rely on PCR as your only tool for protecting yourself against the virus. Like all other management tools it is just that and must be used in conjunction with other techniques to maximize its potential. Selecting larval suppliers that have a history of remaining free of the problem is one very useful tool as are others.

What can you do to lessen the impact of this disease on your farms and hatcheries?

There are some things that you can control and others that you can not.

What management techniques are going to be useful?

Do not buy nauplii or PL’s from a source that could be or is infected with the virus. It is likely that iodine and water washes remove and destroy the virus when used on eggs, nauplii and PLs. It is essential that this process be consistent. Hatcheries must maintain good biosecurity measures and examine each batch of animal. The hatchery needs to be constructed to prevent the introduction of the virus from the ocean.

Use the most sensitive and reliable diagnostic tests available to detect and monitor WSSV. These are going to be DNA based technologies such as PCR and in-situ-hybridization (ISH) of tissue lesions.

Sample hatcheries at least twice during the production cycle and retain samples for later testing (three weeks post shipping).

Only buy PCR screened and stress tested animals. Starting out with no or a very low virus load is important.

Stressing PL’s with formalin has been found to weed out weaker animals though one should never stock PLs that are known to be carrying the virus. It has been noted that in P. japonicus, the virus may not display its pathogenicity till after PL6, making the screening of later stage animals essential.

Minimize the stress on the shrimp wherever possible

There are some ways that you can do this and many that you can not. Some of the things that you can do are:

• increase acclimation times before stocking
  
  

• use non-specific immune stimulants (NSIS) and fortified mineral and vitamin diets to increase stress tolerance
  
  

• Consider stocking during times of the year that you know there will not be experiencing severe stresses from sudden changes in temperature and salinity. It has been reported that these types of stresses can precipitate an epizootic in a population that carries the virus.
  
  

• use good quality diets and continue the use of NSIS through out the life cycle
  
  

• stock at lower densities
  
  

• Monitor for the presence of vectors carrying WSSV in the ponds and control them.

Sample the phyto and zooplankton in the pond before stocking and test by PCR for WSSV. Positive ponds should be avoided.

Sample your ponds frequently. Assure that sick and dying animals and any unusual patterns of mortality are sampled as a routine by PCR and/or histopathology. At the first sign of a problem, harvest the shrimp if you can.

What are some of the ways that other countries manage this disease?

It is believed that one of the major methods for the movement of this virus (and others) has been the movement of infected PL’s. If this can be stopped, it should lessen the rate of spread of the virus. Many countries have taken steps to ensure this though how successful they will be will only be apparent with time. Once the virus gains a foothold it appears that it is there to stay. Fortunately as with all of the other viral diseases such as BP, IHHN, TSV, and MBV, the impact of the disease will lessen with time.

The Thai’s use a variety of tools to deal with the virus, some of which will be useful for P. vannamei. It is important to recognize the differences between the two forms of shrimp culture and understand that there are some difficulties associated with using the same tools to try and control the presence of the virus.

One recommendation made to and by Thai farmers is to use pesticides to kill the vectors before stocking the ponds. Usually a very potent pesticide is added to the water to kill any crustaceans and other vectors that might be present in the pond carrying the virus. This can not be done on the scale that would be required in most of the Americas. The costs would be quite high and the huge amounts of pesticides that would have to be dumped into the ecosystem are not desirable. This should be discouraged and only considered as a very last resort.

Filtering intake water into the pond is one viable approach to eliminating some vectors. Conventional filters may be problematic in the Americas due to the large demands for water. Though this demand can be moderated and relatively small amounts of water added to the system. Filters that use plant fibers to trap everything in conjunction with serial mesh filtration might be useful. Using 250 micron or smaller mesh filters including small mesh bags can be helpful as well.

Another recommendation is to avoid the exchange of water. There appears to be some merit in this in that recent outbreaks of WSSV in S. Carolina in the USA have been associated with the addition of water to ponds. Whether this stressed the shrimp and set off an epizootic or introduced vectors and virus into the ponds is not known. In intensive systems, aeration is used while it is not in semi-intensive systems. The ability to aerate the water mechanically without resorting water exchange might be very useful in those ponds where oxygen levels can not be managed without water exchange.

Animals that are positive for the virus by PCR are not purchased. In some cases it has been reported that screening stocked animals for the presence of the virus has been found to be a useful tool to follow the status of the disease in the population. This can be used to time harvests and to minimize the potential spread of problems to other ponds and/or neighbors.

What you can not control.

Probably the biggest single problem faced by shrimp farmers aside from the actions of their associates will be the sudden environmental fluctuations that accompany the rainy season. Sudden changes in salinity and temperature have been implicated in many outbreaks. As the disease moves from one area to another the viral load in the environment will increase to the point where the virus will be ever present. Ideally shrimp should be destroyed once they are ill to prevent high loads of the virus from entering the environment. Unfortunately this is usually not practical. Harvesting shrimp is and should be encouraged even if shrimp are too small to sell. Cutting losses and minimizing the spread of the virus are to the farmers advantage.

Use Immune Stimulants and optimize Nutrition

All of the data to date suggests that shrimp have relatively primitive immune systems that can not respond to vaccination. In fact it appears that you can not vaccinate shrimp in any sense of the word. Their immune response is short lived, non-specific in nature and provides a modest level of immunity. Though it is possible to exploit this with a variety of polysaccharides, there are very few reports of success using these compounds in the field. The compound with the most field data is a bacterial based material. Lab and field studies have shown a wide range of potential benefits, though like all other tools, these require that they be used as part of on overall management strategy geared towards minimizing the impact of the pathogen.

Animals that have lower levels of resistance due to inadequate nutrition are more susceptible to a variety of problems. Since shrimp in semi-intensive culture environments get between 50 and 70% of their nutrients from natural food source, it is usually difficult to assess what nutrients might be limiting. The role of vitamins A, B, C, D, and E and micro-nutrients such as Selenium are well documented in minimizing the effects of stress and should be routinely added to diets at higher than usual levels at times of stress.

Conclusions:

This virus disease is just one of the many that shrimp farmers will face in the years to come. Effective tools and techniques exist to determine how serious of a problem it can be and to moderate its impact at this time. We are fortunate to have the experiences of others to draw on. The use of PCR in conjunction with other management tools can affect how this disease impacts your bottom line.

Source: Aqua-In-Tech - Reproduced August 2005

Black Ghost

Black Ghost


Black Ghost (Apteronotus albifrons) comes from South America region and are carnivorous. Original habitat temperature 25-28 ° C; pH 6,5-7,0; and hardness 6-10 ° dH. Her form was like a sheet of leaves or a knife with a plain black color and swim vibrate or slide.

Fish is happy with the place was quite dark or dimly lit and will hide when there is a hole, especially in the afternoon. Therefore, in case maintenance is needed provided the hiding place of the roots of trees or paralon pieces. Between males and females difficult to distinguish. Back to the male line a little shorter than females. In addition, the tail fin is narrower in females than males.

Spawning can be done in pairs or mass. Mass spawning with male female ratio 1: 2. However, because the size of the parent can be more than 20 tail then the container should be large enough. Cement pond approximately 1.5 cm x 2.0 m usually be used to memijahkan 20 tails. While the aquarium size 100 cm x 40 cm x 40 cm good enough to accommodate around 5-8 tail stem.


Nest for spawning usually a sheet of fern stems (for orchids) which are stacked or arranged two. Fern stems are crushed stone or fastened so as not to move and sink in water. The eggs of these fish will usually be placed in the holes of the sheet sprayed by ferns.


Generally, spawning took place at night so the morning nest full of eggs can be taken to hatched. Decision nests and eggs should be as early as possible before sunrise. Carried eggs in the aquarium with gentle aeration. Try to place the penetasannya bit dark because the newly hatched larvae can not stand the light.

Laying nest should incline to the wall or the edge of the aquarium so that later the larvae can freely out of the nest.
Eggs will hatch in 2-3 days. The larvae will still be stuck in the nest. After three days, the larvae will swim and feed ready to be given a strained water fleas. The water started to be replaced. Although already able to swim, larvae are still happy to hide in the holes of the nest so the nest should be left until the larvae large enough.


For enlargement, the fish can be given feed silk worms, mosquito larvae and blood worms. Replacement of water must have done every day as much as a quarter of the volume of water when the container of aquarium. If the container in the form of ponds, water replacement is done every 2-3 days. In addition, to the rearing containers should be complemented with a hiding place like pieces stacked paralon to fish more comfortable. Size selling approximately 5 cm achieved at the age of 3 months.

source: Darti S.L and Iwan D. PenebarSwadaya, 2006

topographic engineering requirements of fish ponds

topographic engineering requirements of fish ponds

Technical aspects

In addition to the six socio-economic conditions mentioned above, technical requirements are also important to note. Requirements of this technique include topography, soil, and water.

1. Topography
Topography is the overall shape of the land surface (flat, undulating or steep). Topography is our spotlight for the first time will determine the type, area, number, and the depth of the pond which will be made.
Sloping land once, can not be built units will form the pool for a small pond and the embankment will be wide. This broad embankment works to hold a large mass of water collected underneath. Similarly, if the soil is too flat, it will cost to dig a big land. It also would complicate disposal of water (drainage).


There are six types of places that have character and a special utility for making the pond, which is V-shaped valleys and essentially flat valley '

a. V-shaped valley sharp
Do not ever make a fish pond in the valley because it must make a high embankment to get a small sized pool. This is not efficient because it only cost and energy waste for nothing, while the work is done not on target.


b. The valley is V-shaped bottom is not so sharp
Shaped valley that is still possible to make the pond. It's just made the pool of small size because of the narrow valley bottom. The valley is shaped like better than the first valley, since the causeway made not too wide.

c. The valley is essentially a V-shaped rounded
This valley can be made much wider pool than the V-shaped valley is not so sharp. The main difficulty is to be held at the drying, because the irrigation system had to be made in series.

d. The valley is essentially flat in one of the slope with a stream at the bottom of the other slope
Such areas are relatively easy to build a large pool complex, although forced arranged in series. How to dig a channel at the foot of the first slope and bend of the river as needed so that the river forked in a high place. This artificial channel function provides water supply to the pond that was built between the two channels.


e. Essentially flat valley at the foot of the slope with the river channel in the middle of the plateau region is most ideal for built perkolaman units. Ponds are usually built with a larger size on both sides of the river flow. Thus, in addition to large pool size, the number could be much else. Water source can be obtained by river dam and channel water to make a second income in this valley slopes. The river serves as a channel of water transfer in the event of major flooding or increased so that the pool debitnya free from floods of unwanted.

f. The valley bottom is too flat
Valley with flat topography is not suitable for swimming built units. In addition to the cost of excavating the land, the owner will be difficult to remove or drain the water after the unit is so perkolaman. While a good swimming conditions in addition to easy diairijuga easily dried.



The valley is too flat will have problems when heavy rains come. because the fish pond areas will be inundated by water from the surrounding valley.
source: Heru Susanto, PenebarSwadaya, 2009

Pests and disease prevention in fish Catfish Sangkuriang

Pests and disease prevention in
fish Catfish Sangkuriang

Just like other fish, catfish sangkuriang not be separated from the threat of pests and diseases. Disease affecting sangkuriang catfish most often caused by environmental conditions that are less supportive, such as water quality (especially temperature) under standard or stress due to the fault handling sick fish. Meanwhile, the usual pests attacking sangkuriang catfish include snakes and eels, while organisms that attack pathogenic form Ichthiophthirius sp., Trichodina sp., Monogenea sp., And Dactylogyrus sp.
Poverty entry of pests of seedlings can be done by providing a recommended insecticide when filling the pond water, clean the pond dikes, and put plastic around the pool. Pathogenic organisms prevention can be done with the cultivation of environmental management is good and a regular feeding and inadequate. Treatment can use drugs recommended. environmental management can be done by doing a good pond preparation. If you need to improve the condition of pool water by adding a probiotic material.

Medical suclah fish disease can be done by giving the drug in accordance with the type of illness. Sometimes, a disease that attacks would rub off. To prevent this, there are several steps that can be done rescue as follows. :


- As soon as the fish catch and destroy the disease.
- Immediately move the fish are still healthy condition to the other and sanitize the pool. Reduce solid stocking.
- Do not throw water fish used to channel water sick.
- Drain the pond that had been infected by the disease, then clean the bottom of the pool of mud and organic ingredients. After that Do Calcification using agricultural lime (CaO) with a dose of 1 kg / 5 m2. Drying is done until the bottom cracks crack ¬-lime and stocking done equally, including in the dike.
- Recharge your new water into the pond periodically.
- Equipment and containers of fish caught must be kept so as not contaminated with the disease. Likewise with our hands, should be disinfected by washing them in a solution of PK. Disinfection of instruments made by dipping into a solution of potassium permanganate (PK) 20 ppm (1 g in 50 liters of water) or 0.5 ppm chlorine solution (0.5 g in 1 m3 of water).
- Provide a highly nutritious feed and increase the fish immune system by providing vitamins.

Source: Khairul Amri, S. Pi, M. Si and Khairuman, SP Agromedia Pustaka, 2008

The history and origins of tilapia fish in Indonesia

The history and origins of tilapia fish in Indonesia

Nila fish was first imported from Taiwan to Bogor (Center Fresh Water Fisheries Research) in 1969. A year later, these fish begin to cast to some areas. Indigo naming provisions under the Director General of Fisheries in 1972. The name is taken from this fish species narna, namely nilotica which is then converted into. Name nilotica showed these fish homelands, namely the river

These fish are naturally migrating from its original habitat in the river Nile in Uganda (the upper reaches of the Nile) to the south past kw Raft and Lake Tanganyika to Egypt (along the River Nile). Nila also found in Africa, central and western parts. Largest population is found in fish ponds in Chad and Nigeria. With human intervention, today tilapia has spread around the world starting from the continent of Africa, America, Europe, Asia, and Australia.
Classification
Initially, indigo included in Tilapia nilotica species or tilapia fish from groups that do not lay eggs and larvae in the mouth of its mother. In its development, fisheries experts to rank the species or groups Sorotherodon niloticus tilapia fish that lay eggs and larvae in the mouth of male and female parent. Finally, note that the incubating eggs and larvae ¬ in the mouth of the female parent only. Fisheries experts later determined that the proper scientific name for this fish is or Oreochromis niloticus Oreochromis sp. The following classification more indigo.

Phylum: Chordata
Subphylum: Vertebrata
Class: Pisces
Subclass: Acanthopterigii
Order: Perciformes
Family: Cichlidae
Genus: Oreochromis
Species: Oreochromis niloticus
Foreign Name: nile tilapia
Local Name: nila

Source: Khairul Amri, S. Pi, M. Si and Khairuman, SP, Agromedia Pustaka, 2008

Prawns

Prawns

Prawns (Macrobranchium rosenbergii), including one of the leading commodity fisheries freshwater cultivation of high economic value, but has not developed to its optimum. Currently, besides local prawns are usually cultivated farmers, high yielding varieties also known as prawns gimacro (genetic improvement of macrobranchium rosenbergii) with a faster growth rate and form karapasnya smaller than the size of local prawns karapas that contain meat more.

At the age of five months, the body length of male prawns gimacro reach 38 cm in body weight reached 480 grams per fish. Meanwhile, in the same period, the length of the body of local prawns reaching only 25-28 cm in body weight of only 200 grams per fish. In fact, the maximum size of local prawns ever found in the wild only 300 grams per tail. That's why gimacro prawns prawns known as super because pertumbuhanya very quickly.

prawns added value options when maintenance is relatively brief, lasting from 3 to 5 months. Production level is high, to reach 2 - 5 tons per hectare per crop cycle, from solid tergamtng tebar and technology used. Another advantage prawns survival reaches 80-85% or the death rate not more than 20%
source: Khairul Amri, S. Pi, M. Si and Khairuman, SP, AgroMedia Pustaka, 2008

FISH NILEM (Osteochilus hasselti)

FISH NILEM

Fish Nilem (Osteochilus hasselti) many maintained mainly by farmers in Sumatra (West Sumatra in particular) and in the region of West Java Priangan). In its original habitat, these fish are found living wild in public waters, especially in rivers that have current and water was clear. It also can be found living in a swamp. Nilem known for having a sense of meat and eggs is very tasty. In the area of Sumatra, this fish is often cooked by baking or following dipangek eggs.
Classification
Phyllum: cordata
Class: Pisces
Order: Ostariphysii
Family: Cyprinidae
Genus: osteochilus,
Species: osteochilus hasselti,

Foreign Name: nilem carp, silver shrakminnow
Local Name: Wader nilem or Java), fish or pawas palau (Sumatra), brackish or pujan (Borneo)



b. Morphological characteristics
Nilem elongated body shape and flat. There are two pairs of whiskers on his head. Abdomen reddish color and a greenish brown color back. Color tail fins, anus, and abdomen reddish. Body size of adult fish to reach a maximum length of 35 cm.
Source: Khairul Amri, S. Pi, M. Si and Khairuman, SP, Agromedia Pustaka, 2008

Classification of fish catfish

Classification of fish catfish

At least there are two kinds of catfish are popular and widely grown in cultivation ponds, namely local catfish and catfish Siamese. Here is the classification of each type of catfish it.
- Patin Siam
Phyllum: Chordata
Class: Pisces
Order: Siluriformes
Suborder: Siluroidea
Family: Pangasiidae
Genus: Periopthalmus
Species: Periopthalmus sutchi, or Pangasius sutchi, or Pangasius hypothalmus.
Foreign Name: thai catfish, stripped catfish
Local Name: catfish bangkok, bangkok catfish, Siamese Jambal
- Patin Jambal
Phyllum: Chordata
Class: Pisces
Order: Siluriformes
Sub-order: Siluroidea
Family: Pangasiidae
Genus: Pangasius
Species: Pangasius djambal, or pongosius Pangasius, or Pangasius spp_
Foreign Name: schilbeid catfish
Local Name: Jambal catfish, catfish kipar

source: Khairul Amri, S.Pi. M. Si and Khairuman, S.P, AgroMedia Pustaka, 2008.

Catfish fish morphology

Catfish fish morphology.

catfish fish is one type of fish from catfish groups. The length of adult catfish reached 120 cm. This body size is a measure of body belonging to the fish catfish species. Elongated shape with a dominant color such as silver glittery white on the back and bluish. Body color silvery glow very bright as a child, so many people who keep the aquarium as ornamental fish. This silver color will fade after the larger catfish.

Just like other catfish, catfish do not have the stature aka slippery scales. Form a relatively small head. Her mouth is located at the lower end of the head. In the corner of his mouth are two pairs of whiskers that serves as a search tool feed and tentacle while swimming. At the back there are fins with a strong fingers that can turn into shaft. soft fingers fruit numbered 6-7.
form symmetrical forked tail fin. In the pectoral fin is 12-13 fingers - fingers soft and one hard fingers that function as shaft. Anus fin length, consisting of 30-33 soft radius. Meanwhile, in the belly fins are 6 soft fingers.

source: Khairul Amri, S.Pi. M. Si and Khairuman, S.P, AgroMedia Pustaka, 2008.

Living Conditions and Life Habits patin

Living Conditions and Life Habits

Patin very tolerant of acidity (pH) of water. This fish can survive in waters with a degree of acidity is slightly acidic (low pH) to the alkaline waters (high pH) with pH 5-9. Oxygen content (02) solute needed for the life of catfish are 3-6 ppm. Levels of carbon dioxide (CO2) that can ditoleran is 9-20 ppm. The required level of alkalinity 80-250 ppm. Meanwhile, the optimal water temperature for the growth of catfish is 28-30 ° C.
In its original habitat, the fish is always hiding in holes. As fish nocturnal (active at night), a new catfish out of his hiding hole when it was getting dark. Other habits, this fish is more settled in the bottom-waters than appears on the surface of the water. Therefore, catfish is classified as basic water fish (demersal). This can be proved from the form of a broad mouth like the mouth of demersal fishes in general.
Naturally, catfish feed in the wild form of small fish, worms, detritus (pengurai microbes in the bottom waters), insects, crustaceans, mollusks, and seeds. Based on the various types of these pakannya, catfish are classified as fish-eating everything (omnivores).
The availability of natural seed of common catfish obtained at the end of the rainy season. Based on the research, it is known that fish memijah during the rainy season (November to March). Tool used to catch catfish in the form of seeds or seser nets. Arrest usually done during the wee hours, when the seeds of catfish swimming in the water clusters.
Source: Khairul Amri, S.Pi. M. Si and Khairuman, S.P, Agromedia Pustaka, 2008

Snakeskin

SEPAT SIAM
Snakeskin consists of several types, but the famous are only two kinds of sepat (Trichogaster trichopterus) long, 12 cm maksimuni his clan sepat siam (Trichogaster pectorahs) the maximum body length of 25 cm. Snakeskin first type is not cultivated, while sepat siam a freshwater fishery commodities mainstay widely cultivated.
Snakeskin Siamese inserted into Indonesia from Thailand through Malaysia in 1934. This fish had been cultivated for the first time in Indonesia in 1935. These fish are widely scattered throughout the territory of Indonesia in 1937. Not surprisingly, the Siamese sepat also found living in a swamp.
Siamese Snakeskin is an important economic fish is very popular used as salted fish. Siamese sepat menu is fried salted usually served as a vegetable side dishes complement the menu of popular tamarind in Jakarta and Java Bar • at. Therefore, this type sepat very widely known and cultivated in various regions in Indonesia.


Classification
Phyllum: Chordata
Class: Pisces
Order: Anabantoidae
Family: Belontiidae
Genus: Trichogaster
Species: Trichogaster pectoralis
Foreign names: snakeskinned gouramy, spotted gouramy
Local name: sepat siam
Morphological characteristics
Snakeskin Siamese similar to carp, but has a body size smaller. There are black spots in the middle of the stem tail, this fish lehingga called spotted gouramy. In addition, the color of his piebald like snake skin makes this fish is also named snakeskinned gouramy. Meanwhile, a nickname given because sepat siam than many in Siam, Thailand allegedly given because the shape of a larger body than other types Spat.
Eating Kehiasaan
Siamese Snakeskin is the original fish swamp, from the sweet-water marsh to brackish water swamp. This fish-eating fish belong to all (omnivores). Feed primarily plankton, algae, water plants, and small organisms that live in waters where he grew up.
source: Khairul Amri, S. Pi, MSI, and Khairuman, SP Agromedia library, 2008

Fish Tawes, java carp, silver barb

Tawes


Tawes including one type of freshwater fish are quite popular Indonesian society. Tawes is still small is usually processed into dried salted fish. The reason, this fish is relatively thin and contains little fat, so that when dried in the sun will quickly dry and not smell rancid. Meanwhile, large Tawes cooked in a fresh state for having the taste and aroma of delicious meat, in addition to Indonesia, Tawes can be found in Laos and Vietnam.
Classification
Tawes is one of the original fish that Indonesia country, many found on the island of Java. This is also the cause Tawes has the scientific name Puntius javanicus. However, transformed into Puntim gonionotus, and finally turned into Barbodes gonionotus. This Berikul complete classification.

Pyllum: cordata
Class: Actinopterygii
Order: Cypriniformes
Family: Cyprinidae
Genus: Barbodes
Species: Barbodes gonionotus
Foreign Name: java carp, silver barb
I
Local Name: Tawes, taweh or alum, lampam Java
Source: Khairul Amri, S. Pi, M. Si and Khairuman, SP Agromedia Pustaka, 2008

Production Methods for the Whiteleg Shrimp

The whiteleg shrimp is native to the Eastern Pacific coast from Sonora, Mexico in the North, through Central and South America as far South as Tumbes in Peru. This fact sheet produced by the Food and Agriculture Organisation of the United Nations explains how the different systems of Whiteleg Shrimp production work.

Production

Production Cycle

Production cycle of Penaeus vannamei

Production System

Seed supply

Captured wild seeds were used in Latin America for extensive pond culture of Penaeus vannamei until the late 1990s. Domestication and genetic selection programmes then provided more consistent supplies of high quality, disease free and/or resistant PL, which were cultured in hatcheries. Some were shipped to Hawaii in 1989, resulting in the production of SPF and SPR lines, leading to the industry in the United States of America and Asia.

Broodstock maturation, spawning and hatching

There are three sources for broodstock P. vannamei:

• Where they occur naturally, broodstock are sea-caught (usually at 1 year of age and weighing >40 g) and spawned.
• Cultured shrimp harvested from ponds (after 4–5 months at 15–25 g), are on-grown for 2–3 months and then transferred to maturation facilities at >7 months of age when they weigh 30–35 g.
• Purchased from tank-reared SPF/SPR broodstock from the United States of America, (at 7–8 months of age and weighing 30–40 g).

Broodstock are stocked in maturation tanks in dark rooms supplied with clean, filtered seawater. Feeds consist of a mixture of fresh and formulated broodstock feeds. One eyestalk from each female is ablated, leading to repeated maturation and spawning. Females of 8–10 months of age reproduce effectively, whilst males peak at >10 months. Spawning rates of 5–15 percent/night are achieved, depending upon broodstock source. Females are either spawned in communal or individual tanks (to avoid disease transmission). The following afternoon, the healthy nauplii are attracted by light, collected and rinsed with seawater. They are then disinfected with iodine and/or formalin, rinsed again, counted and transferred to holding tanks or directly to larval rearing tanks.

Hatchery production

Hatchery systems range from specialized, small, unsophisticated, often inland, backyard hatcheries to large, sophisticated and environmentally controlled installations, together with maturation units. Nauplii are stocked into flat, or preferably 'V' or 'U' shaped tanks with a volume of 4–100 m³, made from concrete, fibreglass or other plastic lined material. The larvae are either cultured to PL10–12 in a single larval rearing tank, or harvested at PL4–5 and transferred to flat-bottomed raceways/tanks and reared to PL10–30. Survival rates to PL10–12 should average >60 percent. Water is exchanged regularly (at 10–100 percent daily) to maintain good environmental conditions. Feeding normally consists of live food (microalgae and Artemia), supplemented by micro-encapsulated, liquid or dry formulated diets. From hatching, it takes about 21 days to reach harvest at PL12. Care is taken to reduce bacterial/pathogen contamination of the larval facilities using a combination of periodic dry-outs and disinfections, inlet water settlement, filtration and/or chlorination, disinfection of nauplii, water exchange and the use of antibiotics or (preferably) probiotics.

Nursery

Most farming operations for P. vannamei do not use nurseries, but transport PL10–12 at reduced temperature either in plastic bags or oxygenated transportation tanks to the pond and introduce them directly. In some instances, nursery systems are used and comprise separate concrete nursery tanks or earth ponds, or even net pens or cages located within production ponds. Such nursery systems may be used for 1–5 weeks. Nurseries are useful in colder areas with limited growing seasons, where PL are nursed to a larger size (0.2–0.5 g) in heated tanks/ponds, before stocking into ponds. The use of super-intensive, temperature-controlled, greenhouse-enclosed, concrete or lined raceways have given good results in the United States of America.

Ongrowing techniques

Ongrowing techniques can be sub-divided into four main categories: extensive, semi-intensive, intensive and super-intensive, which represent low, medium, high and extremely high stocking densities respectively.

Extensive

Commonly found in Latin American countries, extensive grow-out of P. vannamei is conducted in tidal areas where minimal or no water pumping or aeration is provided. Ponds are of irregular shape, usually 5–10 ha (up to 30 ha) and 0.7–1.2 m deep. Originally, wild seeds entering the pond tidally through the gate, or purchased from collectors were used; since the 1980s hatchery reared PL are stocked at 4–10/m². Shrimp feed mainly on natural foods enhanced by fertilization, and once-daily feeding with low protein formulated diets. Despite low stocking densities, small shrimp of 11–12 g are harvested in 4–5 months. The yield in these extensive systems, is 150–500 kg/ha/crop, with 1–2 crops per year.

Semi-intensive

Semi-intensive ponds (1–5 ha) are stocked with hatchery-produced seeds at 10–30 PL/m²; such systems are common in Latin America. Regular water exchange is by pumping, pond depth is 1.0–1.2 m and aeration is at best minimal. The shrimp feed on natural foods enhanced by pond fertilization, supplemented by formulated diets 2–3 times daily. Production yields in semi-intensive ponds range from 500–2 000 kg/ha/crop, with 2 crops per year.

Intensive

Intensive farms are commonly located in non-tidal areas where ponds can be completely drained, dried and prepared before each stocking, and are increasingly being located far from the sea in cheaper, low salinity areas. This culture system is common in Asia and in some Latin American farms that are trying to increase productivity. Ponds are often earthen, but liners are also used to reduce erosion and enhance water quality. Ponds are generally small (0.1–1.0 ha) and square or round. Water depth is usually >1.5 m. Stocking densities range from 60–300 PL/m². Heavy aeration at 1 HP/400–600 kg of harvested shrimp is necessary for water circulation and oxygenation. Feeding with artificial diets is carried out 4–5 times per day. FCRs are 1.4–1.8:1.

Since the outbreak of viral syndromes, the use of domesticated disease free (SPF) and resistant (SPR) stocks, implementation of biosecurity measures and reduced water exchange systems have become commonplace. However, feed, water exchange/quality, aeration and phytoplankton blooms require carefully monitoring and management. Production yields of 7–20 000 kg/ha/crop, with 2–3 crops per year can be achieved, up to a maximum of 30–35 000 kg/ha/crop.

In the 'bacterial floc' system, the ponds (0.07–1.6 ha) are managed as highly aerated, recirculating, heterotrophic bacterial systems. Low protein feeds are fed 2–5 times per day, in an effort to increase the C:N ratio to >10:1 and divert added nutrients though bacterial rather than algal pathways. Stocking at 80–160 PL/m², the ponds become heterotrophic and flocs of bacteria are formed, which are consumed by the shrimp, reducing dependence on high protein feeds and FCR and increasing cost efficiency. Such systems have realized productions of 8–50 000 kg/ha/crop in Belize and Indonesia.

Super-intensive

Recent research conducted in the United States of America has focused on growing P. vannamei in super-intensive raceway systems enclosed in greenhouses, using no water exchange (only the replacement of evaporation losses) or discharge, stocked with SPF PL. They are thus biosecure, eco-friendly, have a small ecological footprint and can produce cost-efficient, high quality shrimp. Stocking 282 m² raceways with 300–450 0.5–2 g juveniles/m² and ongrowing for 3–5 months has realized production of 28 000–68 000 kg/ha/crop at growth rates of 1.5 g/week, survivals of 55–91 percent, mean weight of 16–26 g and FCRs of 1.5–2.6:1.

Feed supply

P. vannamei are very efficient at utilizing the natural productivity of shrimp ponds, even under intensive culture conditions. Additionally, feed costs are generally less for P. vannamei than the more carnivorous P. monodon, due to their lower requirement for protein (18–35 percent compared to 36–42 percent), especially where bacterial floc systems are used. Feed prices for P. vannamei range from USD 0.6/kg in Latin America and Thailand to USD 0.7–1.1/kg elsewhere around Asia; FCRs of 1.2–1.8:1 are generally obtained.

Harvesting techniques

Extensive and semi-intensive ponds are harvested by draining the pond at low tide through a bag net installed in the outlet sluice gate. If the tide does not allow harvesting, the water can be pumped out. In some larger farms, harvesting machines pump shrimp and water up to the pond bank where they are dewatered. Intensive ponds may be harvested similarly and small 2–6 man seine nets are dragged around the pond to corral shrimp to the side of the pond from where they are removed by cast or dip net or perforated buckets.

Partial harvesting is common in Asian intensive culture after the first 3 months. In Thailand, artificial sluice gates are temporarily installed inside one corner of the pond to harvest closed system ponds. Shrimp are then trapped in nets attached to this temporary gate when the pond is pumped out.

In super-intensive systems, the shrimp are simply harvested with large scoop nets when required for processing.

Handling and processing

If shrimp are sold directly to processing plants, specialized teams for harvesting and handling are commonly used to maintain shrimp quality. After sorting, shrimp are washed, weighed and immediately killed in iced water at 0–4 °C. Often sodium metabisulphate is added to the chilled water to prevent melanosis and red-head. Shrimp are then kept in ice in insulated containers and transported by truck either to processing plants or domestic shrimp markets. In processing plants, shrimp are placed in iced bins and cleaned and sorted according to standard export sizes. Shrimp are processed, quickly frozen at -10 °C and stored at -20 °C for export by ship or air cargo. Due to an increasing demand, no taxes and higher profit margins, many processing plants operate value-added product lines.

Production costs

Production costs vary depending on many factors. Operational costs for seed production averages USD 0.5–1.0/1 000 PL, whilst sales prices vary from USD 0.4/1 000 PL8–10 in China and USD 1.0–1.2/1 000 PL12 in Ecuador to USD 1.5 3.0/1 000 PL12 around Asia. Lower feed costs and higher intensity levels result in mean production costs for ongrowing of approximately USD 2.5–3.0/kg for P. vannamei, compared to USD 3.0–4.0/kg for more extensive P. monodon culture.

Ammonia in water system

by Ruth Francis-Floyd, Craig Watson, Denise Petty, and Deborah B. Pouder, University of Florida IFAS Extension.
from http://www.thefishsite.com/

Introduction

Ammonia causes stress and damages gills and other tissues, even in small amounts. Fish exposed to low levels of ammonia over time are more susceptible to bacterial infections, have poor growth, and will not tolerate routine handling as well as they otherwise would. Ammonia is a killer when present in higher concentrations, and many unexplained production losses have likely been caused by ammonia.

Ammonia accumulates easily in aquatic systems because it is a natural byproduct of fish metabolism. All animals excrete some waste in the process of metabolizing food into the energy, nutrients, and proteins they use for survival and growth. In fish, the principal metabolic waste product is ammonia. Because it is continuously excreted and potentially lethal, successful aquaculture operations must therefore incorporate methods to detect and eliminate ammonia before it can accumulate and harm fish.

A byproduct of protein metabolism, ammonia is primarily excreted across the gill membranes, with only a small amount excreted in the urine. The decay of uneaten feed and organic matter create small amounts of ammonia, but in most aquaculture systems, fish themselves are the primary source of the compound. The more feed a fish receives, the more ammonia it will produce. However, even a starved fish will produce some ammonia.

Ammonia may be present in city or well water. Even trace amounts can be toxic to fish, and ammonia is colorless, and, in small amounts, odorless. Therefore, the only way for an aquarist or producer to know if ammonia is present is to test the water.

In water, ammonia occurs in two forms, which together are called total ammonia nitrogen, or TAN. Chemically, these two forms are represented as NH₄+ and NH₃. NH₄+ is called ionized ammonia because it has a positive electrical charge, and NH₃ is called un-ionized ammonia (UIA) because it has no charge. This difference is important to know because NH₃, un-ionized ammonia, is the form more toxic to fish. Both water temperature and pH affect which form of ammonia is predominant at any given time in an aquatic system.

The Nitrogen Cycle

A biological process called the nitrogen cycle eliminates ammonia from the water by converting it to other, less toxic compounds (Figure 1). The ammonia fish excrete is converted to a compound called nitrite (NO₂-) by several genera of bacteria, including Nitrosospira and Nitrosomonas. Other groups of bacteria, including Nitrospira and Nitrobacter, convert nitrite to nitrate (NO₃-).

Figure 1. The nitrogen cycle. Nitrifying bacteria use oxygen and alkalinity to convert ammonia and nitrite into the less toxic byproduct, nitrate, which is then used by plants or returned to the atmosphere.

In ponds, this process takes place in the surface layers of the mud, and on plants or other structures. In tanks or aquaria, a biological filter, or biofilter, must be provided as a place where the bacteria can live and flourish. A new biofilter requires six to eight weeks to build up sufficient bacteria to effectively reduce ammonia and nitrite levels.

Other important points to mention about the nitrogen cycle are that both groups of nitrifying bacteria need oxygen and alkalinity to function. If oxygen levels are not sufficient, the process can break down, and ammonia and nitrite levels will increase. Alkalinity (bicarbonate and carbonate) is also used by the nitrifying bacteria. If alkalinity is less than 20 mg/L, the nitrifying bacteria will not be able to function.

It's also important to note that nitrite is toxic to fish at levels as low as 0.10 mg/L. If the biofilter is immature or impaired, adding chloride in the form of salt (sodium chloride) or calcium chloride at the rate of 10 mg/L chloride for each 1 mg/L nitrite will reduce the toxic effects of nitrite on fish.

Nitrate, the end product of the nitrogen cycle, is considered to be harmless to fish in natural systems and ponds as it is used as a fertilizer by plants, including phytoplankton. In closed systems with little or no water exchange, however, nitrate will accumulate and may be harmful if higher than 250 mg/L.

Ammonia Testing

All aquaculturists and hobbyists should invest in a water quality test kit. A good water quality management program will reduce fish disease problems, promote growth, and lessen the need for chemical treatments. A water quality test kit will pay for itself many times over, both in numbers of fish saved and increased production.

Most commercial ammonia test kits measure the total ammonia nitrogen (TAN). Again, it is the un-ionized ammonia (or UIA) portion of the TAN that is more toxic. The UIA fraction of the total TAN can be determined from the TAN measurement if you know the temperature and pH of the water. At high temperatures and high pH, there is more UIA. Therefore, a good ammonia test kit will include a TAN test, a pH test, and a thermometer.

There are two types of ammonia test kits, and each uses a different testing method to determine TAN. One is the Nessler's method and the other is the ammonia salicylate method. If formalin or formalin-containing products have been used within 24-72 hours to treat fish for parasites, the Nessler's method will result in a falsely elevated ammonia reading. Use of ammonia binding products will also cause false high ammonia readings with the Nessler's method. The reagent used in the Nessler's method contains a small amount of mercury that in many states must be disposed of as hazardous waste.

The other testing method is the ammonia salicylate method. This method is not affected by ammonia binding products or formalin treatments. The ammonia salicylate method is also more accurate than the Nessler's method when testing ammonia in seawater, and it does not require disposal of a hazardous waste.

When Should Ammonia Be Tested?

If stocking densities are high, ammonia should be tested every 10 to 14 days in ponds, and at least once a week in tanks. If multiple tanks depend upon a common biofilter (i.e., a recirculating system), there is no need to check every tank individually. Keep records for all tests, and whenever ammonia is found, increase the frequency of testing until the problem is corrected. Whenever fish are sick, test the water quality.

Ammonia is responsible for more unexplained losses in aquaculture than any other water quality parameter. As previously mentioned, it is colorless and odorless, so the only way to know if it is present is to test for it. Fish submitted to a diagnostic laboratory are tested for diseases (bacteria, parasites, fungi or viruses) only. It is the responsibility of aquarists and producers to test the water quality, which is very likely to be the underlying problem.

Interpreting the Ammonia Test

Figure 2.

Figure 3

In healthy ponds and tanks, ammonia levels should always be zero. Presence of ammonia is an indication that the system is out of balance. Therefore, any ammonia in a pond or tank should alert the producer to start corrective measures. Un-ionized ammonia (UIA) is about 100 times more toxic to fish than ionized ammonia.

This UIA toxicity begins as low as 0.05 mg/L, so the result of the TAN test needs to be further calculated to find the actual concentration of UIA. To do this calculation, the temperature and pH need to be measured. Once the pH and temperature are known, the fraction of UIA can be calculated using a multiplication factor found in Table 1. Find the temperature on the top row of the table, and the pH in the left column. The number at which the appropriate column and row intersect in the table is multiplied by the TAN to give the UIA in mg/L (ppm).

This calculation is summarized in Figure 2 and an example is given in Figure 3. Anytime the UIA is higher than 0.05 mg/L, the fish are being damaged. As the concentration rises above 0.05 mg/L, it causes more and more damage. At 2.0 mg/L, the fish will die. Again, any ammonia indicates a problem in your system. If you find it, take corrective measures immediately.

Management of an Ammonia Problem

The first thing to do when ammonia is present in a pond or tank is to reduce or eliminate feeding. Fish are not likely to eat during periods of ammonia stress and the uneaten feed will only make the situation worse. Overfeeding is a major cause of high ammonia concentrations, and stopping the feeding will allow the natural nitrogen cycle to "catch up" with the nutrient load. If at all possible, a 25 per cent to 50 per cent water change will help to remove some of the ammonia. This is only feasible in small ponds or tanks, so don't try to solve an ammonia problem in a large pond by this method.

Low levels of dissolved oxygen limit the ability of nitrifying bacteria to convert ammonia and nitrite, so it is important to monitor dissolved oxygen.

In ponds, the addition of a phosphate fertilizer may help to relieve high TAN levels over a period of days by stimulating phytoplankton growth, which helps remove ammonia from the system; however, it may not help quickly enough in an acute ammonia crisis. Use a 0–20–0 fertilizer at a rate of 40 pounds per acre. It is important not to use a fertilizer that contains nitrogen because nitrogen will add to the problem. If phosphorus is not a limiting factor for algal growth in the pond, the phosphate fertilizer method will not work at all.

In tanks without a biofilter, the producer or aquarist should consider incorporating one. Given the six to eight weeks necessary to establish a biofilter, this will not help in a crisis, but it is a long-term solution to the problem.

In the short term, water changes and the use of ammonia binding products will alleviate ammonia toxicity. It's important to remember that these are short-term solutions. For long-term management, it's best to establish a biofilter.

Some chemicals used to treat diseases in fish, especially antibiotics, can be detrimental to the nitrifying bacteria in the biofilter. Both ammonia and nitrite levels should be tested more frequently after applying a disease treatment, to ensure that the biofilter is still functioning.

Summary

Ammonia is a major waste product of fish and the breakdown of feed and other organics. It can accumulate in aquaculture or aquarium systems, where it will, at the very least, decrease production. It is frequently a stressor that leads to disease, and in other cases it kills fish directly. The only way to detect its presence is to test for it. A fish farmer or aquarist should invest in a water quality test kit, learn how it works, and use it regularly.

Ammonia test kits only measure the total ammonia nitrogen (TAN). When this test indicates a reading above zero, producers or aquarists can determine the fraction of toxic un-ionized ammonia (UIA) after measuring pH and temperature. The multiplication factors are found in Table 1, and an example calculation is found in Figure 3.

When ammonia is present, the fish in the system should not be fed until the problem is corrected. In small systems, a water change will help, and in large ponds, a 0–20–0 fertilizer may help.

Test for ammonia regularly and take corrective measures as soon as you detect it. Severe problems may occur when tests are not performed frequently enough. Once fish have started to die, it is difficult to correct an ammonia problem without losing more fish.

Ammonia in Aquatic Systems

Table 1. Fraction of un-ionized ammonia in aqueous solution at different pH values and temperatures. Calculated from data in Emmerson et al. (1975). To calculate the amount of un-ionized ammonia present, the Total Ammonia Nitrogen (TAN) must be multiplied by the appropriate factor selected from this table using the pH and temperature from your water sample. See the example in Figure 3.

Shrimp Market Report - September 2009 - Asian Markets

The cherry blossom season in Spring induced outdoor eating and business improved at the catering trade during April-May, according to a report prepared by Fatima Ferdouse for FAO Globefish.

However, as price control is exercised carefully to avoid consumer backlash, the catering and retail trade have moved to make cheaper products available to end consumers.

Subsequently, demand for large sizes shrimp did not improve much during the Golden Week festival compared to the previous years. The festival demand for X–large sizes namely 6/8 through 13/15 was disappointing for the catering trade.

Imports during the first quarter of the year fell behind last year’s. Shrimp prices at wholesale trading; however, were stable during this period following reduced imports during the first quarter of the year.

MARKET TRENDS

The H1N1 flu (known as Mexican flu in Japan) alarm has created mixed trends in the market. Due to the health scare, people are avoiding going out, which is hurting the already soft restaurant trade. Supermarkets, on the other hand, report increasing sales of frozen food including processed and prepared shrimp as more meals are prepared or eaten at home. Usage of cooked and peeled shrimp has increased at pizza outlets.

Due to the shrinking business in the catering trade, imports of sushi shrimp will be lower this year. Less traveling during this summer holiday will also take a toll on the already affected catering trade.

In a seasonally dull market in hot and humid summer, trading is sporadic for small lots and selective sizes at wholesale/distribution level. Prices have weakened further for 16/20 counts b/tiger shrimp, for which demand is extremely poor and local stocks are high. This downward price movement also affected prices for the mid- range counts (21/25 and below). Supply shortage from Kolkata area may reverse the situation. Supermarket demand for frozen vannamei is better; prices are under pressure due to improved harvests in southeast Asian countries.

Processed shrimp: Household demand has improved for frozen cooked and prepared shrimp. Usage of pud/p&d, and PTO has also increased at food delivery services; vannamei shrimp sells better due to the price factor. However, demand for sushi shrimp (vannamei) from the Kaiten sushi chains is seriously affected by the slowing restaurant trade.

Import/Export Trade: Lack of real demand in the market have weakened prices of 16/20 counts headless shell-on black tiger shrimp. Japanese buyers’ demand is more for sizes 21/25 and below for which prices are stable as supplies of these sizes are still limited in producing countries. By late May price of Vietnam origin 16/20 fell by US$ 30-50 cents/kg, as shipments consisted more of the large sizes. However, supplies of the preferred mid sizes have improved from this source. But imports from Kolkata (India) packers are affected because of the following the cyclone in late May.

SUPPLY

Myanmar: Black tiger shrimp harvest in Myanmar is forecast to be lower than last year. The farming season has started in April/May but there is very little interest among the farmers practicing semi-extensive aquaculture as the leading market Japan remains unattractive to them. Subsequently black tiger shrimp hatcheries are inactive and many farmers have shifted to soft-shell crab aquaculture. Only extensive farms practising ‘catch and hold’ operations are expected to produce farmed black tiger shrimp this year.

India: As of 1 April 2009, the Government of India has introduced a new ruling which allows only antibiotic-free certified farmed shrimp to be processed for export markets. The authorized laboratories of the Marine Products Export Development Authority of India (MPEDA) will be responsible for checking and certifying according to the required quality (antibiotic-free) standards of farmed shrimp for exports. Meanwhile, in the southwestern shrimp farming belt, many farms producing black tiger shrimp, are getting fully integrated (hatchery/ feed mill/ grow out) to guarantee antibiotic-free harvests.

To meet their Japanese importers requirement, farmers in West Bengal (Kolkata) have started to produce more medium counts (21/25 counts and below) of black tiger shrimp. But in late May, farming in this area has been seriously damaged by the cyclone Aila. High tidal waves, caused damage to 50-60 per cent of the farms and infrastructure and washed away crops which were in the middle of the peak farming season. In southern India, raw material supplies are still lower than expected.

Bangladesh: Black tiger shrimp farms in Khulna/Shatkhira area in Bangladesh are also seriously damaged by the cyclone Aila.

Vietnam: Discouraged by the falling prices of shrimp in the export markets, black tiger shrimp production is scaled down in the southern provinces of Vietnam. As of end March, nearly 8 per cent of the farming area in the country was not prepared for the new season. The most affected provinces are Ca Mau and Bac Lieu where many processing plants are forced to reduce their production by 35-40 per cent. Harvests of black tiger shrimp from this areas are mainly consisted of larges shrimp for which consumer demand is very weak in Japan.

On the converse, there is a surge in farming vannamei shrimp in the southern provinces. This year vannamei production may reach 100 000 MT in Vietnam.

Thailand: Overall production of farmed shrimp dropped 15 per cent during January-March 2009 compared to the same period last year; According to the country’s Shrimp Farmers Association, this year’s production may come down to 392 000 MT compared to 490 000 MT harvested last year. The production cut will be more for vannamei, compared to the black tiger shrimp.

Indonesia: The disease problem occurred in some farming vannamei areas is reportedly under control. Some government sources indicate that overall production may increase by some 20-30 per cent this year. However, with further strengthening of Indonesian Rupiah against the US dollar, current prices in the export market do not compensate the raw material prices. Last year 300 000MT of farmed shrimp were harvested in Indonesia.

IMPORTS

Compared to last year, cumulative imports of shrimp during January-March 2009 increased by three per cent to 566 396 MT against the same period last year. In the coming months, supplies for semi-processed and processed vannamei from Thailand are expected to increase compared to shell-on products. As for black tiger shrimp, market demand for 21/25 and smaller counts will persist.

OUTLOOK

In the international arena, import volume and prices will be largely influenced by the economic situation in the country. Price and convenience will continue to be the key factors affecting consumer demand for the rest of the year in Japan. Consumer spending in Japan has reduced to an extent not witnessed in recent history. However, the increase in home meal preparation is expected to improve household demand for shrimp; semi-processed and processed shrimp will benefit more from this development.

Requisitions from restaurants will be lower than last year due to the downward trends in business. The scheduled marketing plan for the coming summer holiday may also be affected, if the “H1N1 flu” scare prolongs longer.

September 2009

Future Prospects of Monosex Tilapia Culture in Thailand

Since its adoption for aquaculture Nile tilapia (Oreochromis niloticus) has proven popular for its ease of culture, robustness, palatability, and tolerance of a range of environmental conditions, say Belton, B., Turongruang, D., Bhujel, R. and Little, D.C. This report was published by the Network of Aquaculture Centres Asia-Pacific.

Origins

The fishes’ reproductive behaviour was originally seen as one of its most valuable characteristics, making it unnecessary for small-scale farmers to repeatedly purchase hatchery produced seed, and contributed to its promotion and distribution for rural development purposes throughout the tropics.

The sub-optimal growth and low or variable size (and market value) which mixed-sex populations of tilapia frequently exhibited acted as a constraint to the species commercial development however, leading to efforts in the 1970’s to produce all-male fry in order to circumvent the problem. Despite the obvious promise of such a technical breakthrough no suitable technology for reliably producing all-male tilapia at a commercially viable scale and cost emerged until the mid 1980s.

Development of hapa-based broodstock management, which allowed for collection of tilapia eggs and yolk-sac larvae of a uniform age, proved the key to ensuring consistently high (~99%) levels of male fish following the application for 21 days of feed treated with 17-α methyltestosterone. This breakthrough occurred as a result of doctoral research initiated at the Asian Institute for Technology (AIT) in 1984 as part of an EU funded project on the intensification of septage-fed aquaculture systems. Right; Feeding red tilapia in riverine cages, Ang Thong province.

AIT staff immediately recognised the wider implications of the technology and began to increase production of monosex fry for use in experimental trials, and for sale to forward-thinking commercially oriented fish farmers in Central Thailand who were also quick to grasp the potential of all-male tilapia. Word of the benefits spread rapidly among this group following the publication of articles in local popular media, and the Institute began promotion monosex seed to small-scale farmers in NE Thailand as part of its development focussed extension activities there, as a result of which it expanded hatchery production to a peak of two million per month in early and mid 1990’s.

AIT also worked closely with the Thai Department of Fisheries (DOF) to institutionalise adoption of the technology from the late 1980’s, and established a short course training program for monosex hatchery production as part of its remit for disseminating development focussed research outputs. Short courses attracted more than 100 participants from the public and private sector both locally and internationally but their efficacy initially proved somewhat limited, prompting key staff to seek to extend impacts to the private sector through mentoring and support for, and partnership with, private hatcheries.

Development of the hatchery sector

The first informal partnership began in 1987 with the provision of advice and training to a charitable foundation in Udorn Thani. This facilitated the establishment of a monosex tilapia hatchery to provide a source of income with which the foundation could fund its other rural development activities. Former employees of the foundation operate a hatchery on a similar basis at a different location in Udorn Thani to this day.

1991 saw the birth of a more formal joint venture with an existing hatchery, Rom Sai Farm in Ayutthaya, under which AIT personnel oversaw the construction and operation of a monosex production facility. This was a significant development, increasing the availability of all-male seed in Central Thailand at a key point in the technology’s uptake, but technical and management difficulties ultimately put an end to the collaboration.

In 1993 Manit Farm, a large shrimp and tilapia growout farm in Petchaburi, which had been an early adopter of all-male tilapia seed, established a monosex hatchery of its own after its demand for seed exceeded the production capacity of the AIT hatchery. Again, there were close ties to AIT, and Manit Farm recruited an ex-AIT staff member who had worked at Rom Sai Farm to be its hatchery manager. Manit Farm continues to operate successfully today and is one of Thailand’s leading monosex tilapia seed producers. A year later, in 1994, the farm’s hatchery manager left to establish his own monosex tilapia hatchery and growout business, Boonholme Farm in Khon Kean, which remains one of Northeast Thailand’s foremost seed producers and largest pond-based growout farm.

A subsequent joint venture between AIT, a subsidiary company of Cargill, and two local entrepreneurial investors resulted in the startup of Nam Sai Farm in Prachinburi Province in 1994. The company was headed by the former AIT-employed hatchery manager from the earlier venture in Ayutthaya under an agreement by which AIT would provide technical support and expertise for a six year period, receiving a royalty fee from the Cargill subsidiary for each fish produced. Following the end of this arrangement Nam Sai continued as one of the largest monosex hatcheries in the country.

Charoen Phokpand (CP), the Thai agro-industrial giant, initiated commercial production of all-male tilapia seed in 1995 following several years of experimentation. Again, a fairly direct line of technology transfer can be traced to AIT, with CP staff attending short course training there and AIT alumni joining the company’s aquaculture division, but close personal ties played a less critical role than in the earlier start-ups. CP now operates five tilapia hatcheries around the country and produces more all-male tilapia fry than the country’s next three largest monosex hatchery operators combined.

From the late 1990’s onwards the number of monosex hatcheries in Thailand proliferated (to well in excess of 20 at present), as farmer demand for sex-reversed fry increased and knowledge of the necessary hatchery management techniques, once confined largely to individuals associated with the early development of the technology at AIT, became more widely accessible. Knowledge transfer through DOF officers came to play an increasingly important role; mainly by consultancy and advice given unofficially as part of close relationships between hatchery operators and DOF staff. At least three monosex hatcheries were established in this manner, most notably Bor Charoen Farm in Chachoengsao, which is now one of the largest, and certainly the most technologically advanced in the country. In other instances ex-staff of hatcheries including Nam Sai and CP left to start businesses of their own, and several fry agents who had established a customer base by nursing and selling fingerlings for cage culture used this as an entry point into hatchery production.

Although DOF produces small numbers of monosex fry at fisheries research stations throughout the country for use in extension activities and for sale to small-scale farmers and nursing co-operatives it’s most significant contribution by far, aside from the unofficial role described above, has been the provision of high quality broodfish to hatchery owners. At present only four hatchery operators possess the capacity to develop broodstock independently, with the vast majority of the remainder reliant on the government run Aquatic Animal Genetics Research and Development Institute for this service.

Table 1: Name, lodation, date established, knowledge acquistion pathway, and estimated average monthly fry sales for monosex tilapia hatcheries in Thailan

The ability to produce all-male tilapia fry has revolutionised the profile of the species’ production and consumption in Thailand in the last 15 years, bringing about huge changes in productivity, profitability, value, and diversification. The following sections describe associated developments in two distinct sectors; pond and cage culture.

Pond culture

Thai tilapia production has increased, almost exponentially, from an officially recorded 22,800t in 1990 to 203,700t in 20051. This growth can by no means be exclusively attributed to monosex; the advent of improving transport and communications, greater access to agricultural by-products for use as feeds and fertilisers in pond culture, and the increasing size and affluence of urban markets, being critical factors2. However, the existence of tilapia capable of quickly, reliably, and cost efficiently reaching larger sizes (400g-1kg; as opposed to the 250-350g at which mixed sex tilapia were typically harvested) has radically altered the species’ utility to farmers and led to major shifts in marketing strategies and consumer preferences.

Production of cyprinid species – once the mainstay of greenwater polyculture systems that predominated in Thailand – has, with the exception of silver barb (Barbodes gonionotus), all but stagnated over the same period. This far slower rate of growth can be substantially attributed to the progressive dominance of monosex tilapia in pond polyculture. Greenwater polyculture systems in central Thailand are now typically comprised of around 90% monosex tilapia, with assorted carp species (which attract a somewhat lower market value) stocked to fill vacant ecological niches in the pond in order to help maintain water quality.

Farmers stocking monosex tilapia in ponds tend to pursue one of two broad production and marketing strategies. The first, more traditional, system is generally practiced by smaller and medium scale farmers (with holdings in the order of 20-100 rai), in which growout periods of around 8 months facilitate production of tilapia averaging 400-500g. These fish are stored on ice upon harvest, and distributed to fish markets in Central, and to a lesser extent, NE Thailand, and attract a farmgate value in the order of Bt18-20/kg.

Larger farms (100 to >1,000 rai) typically focus on the production of tilapia averaging upwards of 600g. Total growout cycles can last 12-13 months, with partial harvest (thinning out for sale or restocking in other ponds) occurring on two or three occasions, allowing remaining fish to rapidly gain weight. Formulated pellet feeds may be fed during the later stages of growout to assist fattening. Fish are placed in aerated tanks upon harvest for distribution to local markets where they are sold live to demonstrate product freshness to consumers. Large live tilapia attract a considerably higher farmgate price than their dead counterparts (~Bt30/kg).

Production in this manner has become increasingly common in the last five years and now accounts for perhaps 40% of the output of pond culture from the Central region, but is generally only practiced by farmers with sufficient knowledge, experience and space to carefully manage all aspects of growout and staggered harvesting, and with sufficient capital to enable them to defer returns on investment for a year or more. A great many of these originate from a handful of districts in southern Bangkok and Samut Prakan province where commercially oriented pond culture has been widely and successfully practised for over 30 years. These entrepreneurial individuals have expanded operations into provinces including Prachinburi, Nakorn Nayok, Chachoengsao and Ratchaburi where affordable land and labour are more readily available than inside the heavily urbanised Bangkok Metropolitan Region.

Cage culture

The development of pond culture post-monosex can be seen a largely organic affair, resulting from a gradual evolution led by innovative farmers and actors in the marketing chain, and confined primarily to provinces in central Thailand where abundant water, land and feed resources exist. In contrast, the origins of cage-based tilapia culture (which now accounts for perhaps 30% or more of the total output of Thai tilapia) can be traced directly to the research, development and marketing activities of a single corporate entity; CP. The dominant force in Thai agro-industry, CP was already the prime mover in the country’s shrimp industry and a major supplier of feed for walking catfish (Clarius sp.) culture at the point when monosex hatchery production techniques emerged. Initially focussing on production of tilapia for a buoyant export market, CP began experimenting with the development of saline tolerant strains of hybrid (Oreochromis sp.) red tilapia for culture in vacant shrimp ponds on the upper Gulf of Thailand. Although these efforts ultimately proved unsuccessful, in part due to the slow growth of tilapia under these conditions, the company switched its attention to the application of these research outputs to the domestic market. Left: Farmers must share the river with many other users.

The enhanced feeding efficiency of monosex over mixed-sex tilapia (FCRs for cage culture averaging around 1.4 and 1.8 respectively), and the larger size and, hence, value attainable, made the prospect of production based exclusively on formulated diets an economically viable possibility for the first time. Adapting the existing concept of cage-based culture to suit its needs, the company launched a concerted marketing strategy based on a shrewd assessment of regional fish consumption preferences, with the ultimate goal of expanding its market for aquatic feeds.

The company promoted sales of live tilapia through television advertisements, endorsements from high profile chefs, product dumping in markets at below production cost, and the engagement of restaurants and caterers providing set meals at festivals and celebrations. CP’s marketing in central Thailand revolved primarily around a red strain of tilapia (named pla tabtim by the King of Thailand), reflecting a need to differentiate the product from smaller, dead, pond-produced Nile tilapia commonly considered by Thai consumers to be of low quality due to the frequent occurrence of off-flavour. In the N and NE of the country, where pond raised tilapia are far scarcer and live fish are highly sought after, large live Niles proved more compatible with local tastes.

Cage culture of both red and Nile tilapia (based on a contract farming system under which feed and fry produced by the company are supplied to farmers through a network of affiliated dealerships which buy back and market live fish when they attain at a weight of 600g or more) expanded dramatically as a result. Cage-raised fish are now by far the most significant source of tilapia in markets in the northern part of the country, whilst in the central region cage production is limited almost exclusively to red strains. The extent of this division is illustrated by CP’s hatchery output, around one third of which is red and marketed largely in Central provinces, with the remaining two thirds of Nile tilapia fry destined primarily for growout in cages in rivers and reservoirs in the N and NE. This live marketing of fish may also have had unforeseen spill over effects on the development of pond culture, setting a precedent from which the increasing popularity of live pond-produced tilapia described above followed.

CP’s initiative (which is better viewed as an exercise in astute marketing than a major technical advance) has radically influenced the scale and form of tilapia production in Thailand. However, the system - which transfers risks associated with distribution of feed, seed and final product on to its dealerships and, ultimately, cage farmers, allowing the company to pursue capital accumulation via the profitable feed production arm of the business – is typically a less secure proposition for end users than independently developed pond-based production strategies.

That CP now controls perhaps 60% of the production system it created around 10 years ago testifies in part to the less than charitable practices of certain dealerships working under the company (among a range of complaints voiced by farmers, a failure to honour agreements pertaining to the farmgate value of harvested fish and excessively high input costs are some of the most common). The remainder of the market is divided up between several feed companies operating similar ‘integrated’ informal contract systems and farmers producing and marketing fish on an independent basis.

The future of cage-based tilapia production looks increasingly uncertain however; the open nature of cage systems and their location in water bodies impacted by multiple users rendering them vulnerable to a range of adverse environmental factors including pollution episodes, low water levels and/or flow rates (particularly in rivers and reservoirs in the NE), annual flooding events and highly turbid water and, perhaps most critically, disease.

Based on anecdotal reports it appears that the incidence of disease in cage-raised tilapia has become increasingly more severe in the last two years. Annual outbreaks of Streptococcus during the hot dry season have occurred regularly for some time, but these appeared to have been augmented recently by serious parasitic infections and a new and particularly virulent pathogen, possibly Microsporidium which was apparently responsible for very substantial mortalities in April and May of this year.

Current trends and future directions

Cage-based tilapia production now appears increasingly unsustainable from the farmer’s perspective in light of progressively more severe disease problems and water quality and availability issues coupled to the rapidly rising cost of commercial feeds. The alternative, which several particularly well informed interviewees suggest is likely to occur within the foreseeable future, is a comprehensive shift from cage culture in multi-use water bodies to intensive cage-based production in aerated ponds; the latter requiring greater capital investment but far being less vulnerable external environmental pressures. A small number of farmers already practise similar culture techniques, nursing Nile tilapia to 200-300g at high density in greenwater before transferring to cages in ponds for rapid fattening on high quality pellet feeds. White shrimp (Litopenaeus vannamei) and giant freshwater prawn (Macrobrachium rosenbergii) are also stocked in these ponds at low density to provide an additional high value crop.

Numerous other tilapia farmers have also begun stocking shrimp and/or prawn as an additional species and, inversely, it is now commonplace for inland shrimp and prawn farmers to stock tilapia in their systems. In both instances this development appears to be a response to declining profit margins (in the case of tilapia farmers this is due to inflationary pressure on feedstuffs which modest increases in the market value of the fish had been unable to make up for), and has the added benefit of providing some measure of biological control through the removal of detritus and uneaten feeds.

Record prices for Thai rice earlier this year have also brought about some unexpected changes. In one district of Nakorn Pathom, and almost certainly in other areas, a number of small-scale but marginally successful tilapia farmers have, temporarily at least, abandoned pond culture in favour of rice production which is, under normal circumstances, a far lower income activity. In addition it appears that associated increases in the value of rice bran, the most widely used supplementary feed among farmers operating traditional greenwater growout, have made the substitution of low protein formulated feed an economically viable alternative pond input due to the trade-off in reduced growout periods which it facilitates. Whether these trends are likely to continue if rice prices return to more normal levels is open to question, but they underline clearly the intimacy with which fish culture in Central Thailand is bound to other agricultural activities.

Recorded tilapia exports from Thailand are currently fairly meagre (5,128 t in 2006). This figure may under-represent the real volume, considering that national statistics for total tilapia output almost certainly under-report total annual output. However, the likely prospects for expansion of export-led tilapia production remain uncertain. Whilst there may be potential for expansion of Thai exports given the species’ ever greater importance as an internationally traded commodity, Thai producers apparently experience difficulties in competing with those in China for a variety of reasons which may include comparative advantages in the cost of feed production and labour, Chinese government export subsidies, and total production volumes. Perhaps the most significant reason for the failure of the sector to expand to date is that domestic consumption has kept pace with production increases. This has meant that local market values are currently comparable to those for export, providing little incentive to producers to pursue these more demanding markets. However, as production continues to expand and intensify, facilitating the production of greater volumes of consistently large, high quality fish, better capitalised Thai producers may ultimately find it advantageous, and even necessary, to enter the global marketplace in order to dispose of their product.

Acknowledgements:

The authors would like to acknowledge the generous support and assistance provided by AIT’s EU funded Asia-Link Aqua Internship program, Warren Turner and Termsac Kongsamran, and all of the farmers, hatchery operators and other individuals who gave their time in contributing to the research that facilitated the writing of this article.

References

DOF. 2007. Fisheries Statistics of Thailand 2005. Department of Fisheries, Ministry of Agriculture and Cooperatives, Bangkok, Thailand.

Belton, B. and D. C. Little. 2008. The Development of Aquaculture in Central Thailand: Domestic Demand versus Export-Led Production. Journal of Agrarian Change. 8 (1): 123-143.

This article was published in Aquaculture Asia Magazine

August 2009

Freshwater Prawns Pond Production and Grow-Out

Freshwater Prawns Pond Production and Grow-Out - By the Mississippi State University - A final phase of freshwater prawn (shrimp) production is grow-out of juveniles to adults for market as a food product. Research in Mississippi has demonstrated this can be a profitable enterprise, and this publication provides guidelines for stocking and managing a freshwater prawn production pond.

Unless you have a hatchery/nursery, you must purchase juveniles for the pond grow-out phase. Commercial hatcheries in Texas, California, and Mexico produce postlarvae and juveniles. The price is about $60 per 1,000 juveniles. You can minimize shipping costs if the hatcheries are located within a 10- to 14-hour driving distance of your grow-out facility.

Site Selection and Pond Design

Ponds used for raising freshwater prawns should have many of the same basic features of ponds used for the culture of channel catfish. A good supply of fresh water is important, and the soil must have excellent water-retention qualities. Well water of acceptable quality is the preferred water source for raising freshwater prawns. Runoff from rivers, streams, and reservoirs can be used, but quality and quantity can be highly variable and subject to uncontrollable change. The quality of the water source should be evaluated before any site is selected.

Locate ponds in areas that are not subject to periodic flooding. Before building ponds specifically for producing freshwater prawns, check the soil for the presence of pesticides. Prawns are sensitive to many of the pesticides used on row crops. Also, analyze the soil for the presence of residual pesticides. Do not use ponds that are subject to drift from agricultural sprays or to runoff water that might contain pesticides.

The surface area of grow-out ponds ideally should range from 1 to 5 acres. Larger ponds have been successfully used; ideally the pond should have a rectangular shape to facilitate distribution of feed across the entire surface area. The bottom of the pond should be completely smooth and free of any potential obstructions of seining. Ponds should have a minimum depth of 2 feet at the shallow end and a maximum depth of 3.5 to 5 feet at the deep end. The slope of the bottom should allow for rapid draining. You can obtain assistance in designing and laying out ponds by contacting a local office of the Natural Resources Conservation Service (formerly Soil Conservation Service).

Collect a soil sample from the pond bottom to determine whether lime is needed. Take soil samples from about six different places in each area of the pond, and mix them together to make a composite sample that is then air-dried. Put the sample in a soil sample box, available from your county Extension agent, and send it to the Extension Soil Testing Laboratory, Box 9610, Mississippi State, MS 39762, and request a lime requirement test for a pond. There is a charge of $3 per sample for this service.

If the pH of the soil is less than 6.5, you must add agricultural limestone to increase the pH to a minimum of 6.5, and preferably 6.8.

After filling the pond, fertilize the pond to provide an abundance of natural food organisms for the prawns and to shade out unwanted aquatic weeds. A liquid fertilizer, either a 10-34-0 or 13-38-0, gives the best results. Apply 1/2 to 1 gallon of 10-34-0 or 13-38-0 liquid fertilizer per surface acre to the pond at least 1 to 2 weeks before stocking juvenile prawns. If a phytoplankton bloom has not developed within a week, make a second application of the liquid fertilizer. Do not apply directly into the water because it is denser than water and will sink to the bottom; liquid fertilizer should be diluted with water 10:1 before application. It can be sprayed from the bank or applied from a boat outfitted for chemical application.

At least 1 or 2 days before stocking the juvenile prawns, check the pond for aquatic insect adults and larvae that might eat the juvenile prawns. You can control the insects by using a 2:1 mixture of motor oil and diesel fuel at the rate of 1 to 2 gallons per surface acre on a calm day. The oil film on the water kills the air-breathing insects and is more effective when applied on calm days.

If a water source other than well water is used, it is critically important to prevent fish, particularly members of the sunfish family (e.g., bass, bluegills, and green sunfish) from getting into the pond when it is filled. The effects of predation on freshwater prawns by these kinds of fish can be devastating. If there are fish in the pond, remove them before stocking prawns, using 1 quart of 5 percent liquid emulsifiable rotenone per acre-foot of water.

Stocking of Juveniles

Water in which postlarvae and juveniles are transported should be gradually replaced by the water in which they will be stocked. This acclimation procedure should not be attempted until the temperature difference between the transport and culture water is less than 6 to 10 °F. The temperature of the pond water at stocking should be at least 68 °F (20 °C) to avoid stress because of low temperatures. Juvenile prawns appear to be more susceptible than adults to low water temperatures. Juveniles, preferably derived from size-graded populations ranging in weight 0.1 to 0.3 g, should be stocked at densities from 12,000 to 16,000 per acre. Lower stocking densities will yield larger prawns but lower total harvested poundage. The duration of the grow-out period depends on the water temperature of the ponds, and the time generally is 120 to 150 days in central Mississippi. Prawns could be grown year-round if you can find a water source that provides a sufficiently warm temperature for growth.

Feeding

Juvenile prawns stocked into grow-out ponds initially are able to obtain sufficient nutrition from natural pond organisms. At the recommended stocking densities, begin feeding when the average weight of the prawn is 5.0 g or greater. Commercially available sinking channel catfish feed (28 to 32 percent crude protein) is an effective feed at the recommended stocking densities. The feeding rate is based upon the mean weight of the population (Table 1). A feeding schedule has been developed by researchers at the Mississippi Agriculture and Forestry Experiment Station and is based upon three factors:

• A feed conversion ratio of 2.5;
• One percent mortality in the population per week; and
• Mean individual weight determined from samples obtained every 3 weeks.

At the end of the grow-out season, survival may range from 60 to 85 percent, if you have practiced good water quality maintenance. Yields typically range from 600 to 1,200 pounds per acre. Weights of prawns range from 35 to 45 g (13 to 10 per pound).

Water Quality Management

Water quality is just as important in raising freshwater prawns as it is in raising catfish or any other species of aquatic animal. Dissolved oxygen (DO) is particularly important, and a good oxygen monitoring program is necessary to achieve maximum yields. You should routinely check and monitor levels of dissolved oxygen in the bottom one foot of water which the prawns occupy. Electronic oxygen meters are best for this purpose but are rather expensive and require careful maintenance to ensure good operating condition. The need for an electronic oxygen meter increases as the quantity of ponds to be managed increases. With only one or two small ponds, a chemical oxygen test kit is sufficient. Chemical oxygen tests kits that perform 100 tests are commercially available from several manufacturers.

Use a sampler for collecting samples from an appropriate water depth for dissolved oxygen analysis. These sampling devices are commercially available or can be fashioned. It is important the dissolved oxygen concentration in the bottom one foot of water does not fall below 3 parts per million (ppm). Dissolved oxygen concentrations of 3 ppm are stressful, and lower oxygen concentrations can be lethal. Chronically low levels of dissolved oxygen result in less than anticipated yields at the end of the growing season. Emergency aeration can be achieved by an aerator. The design and size of the aerator depend on the size and shape of the culture pond.

Oxygen depletions can be avoided. One method to predict low DO levels is to plot the level an hour after sunset and approximately 2 hours later. Plot these two readings on a piece of graph paper and connect them with a straight line. Oxygen consumption during the late evening and early morning proceeds at a constant rate, caused by the respiration of the animals and plants in the water. By extending the line from these two points over time you can quickly determine if the dawn DO concentration will decrease to a level that will stress or possibly kill the prawns. This method indicates whether emergency aeration is necessary and when to provide it.

Specific information on water quality requirements of freshwater prawns is limited. Although freshwater prawns have been successfully raised in soft water (5 to 7 ppm total hardness) in South Carolina, a softening of the shell was noticed. Hard water, 300-plus ppm, has been implicated in reduced growth and lime encrustations on freshwater prawns. Therefore, use of water with a hardness of 300-plus ppm is not recommended.

Nitrogen Compounds

Nitrites at concentrations of 1.8 ppm have caused problems in hatcheries, but there is no definitive information as to the toxicity of nitrite to prawns in pond situations. High nitrate concentrations in ponds would not be expected given the anticipated biomass of prawns at harvest. High levels of un-ionized ammonia, above 0.1 ppm, in fish ponds can be detrimental. Concentrations of un-ionized ammonia as low as 0.26 ppm at a pH of 6.83 have been reported to kill 50 percent of the prawns in a population in 144 hours. Therefore, you must make every effort to prevent concentrations of 0.1 or higher ppm un-ionized ammonia.

pH

A high pH can cause mortality through direct pH toxicity, and indirectly because a higher percentage of the total ammonia in the water exists in the toxic, un-ionized form. For more information on ammonia in fish ponds, request Extension Information Sheet 1333. Although freshwater prawns have been raised in ponds with a pH range of 6.0 to 10.5 with no apparent adverse effects, it is best to avoid a pH below 6.5 or above 9.5, if possible. High pH values usually occur in waters with total alkalinity of 50 or less ppm and when a dense algae bloom is present. Before stocking, liming ponds that are built in acid soils can help minimize severe pH fluctuations.

Another way to manage to avoid any anticipated problems of high pH is to reduce the quantity of algae in the pond by periodic flushing (removing) the top 12 inches of surface water. Alternatively, organic matter, such as corn grain or rice bran, can be distributed over the surface area of the pond. This procedure must be accompanied by careful monitoring of oxygen levels, which may dramatically decrease due to decay processes.

In some cases, dense phytoplankton growth may occur in production ponds. To control algae, do a bioassay before using any herbicide in a freshwater prawn pond. To do a bioassay, remove a few prawns, put them in several plastic buckets containing some of the pond water, and treat them to see if the concentration of herbicide you plan to use is safe. Be sure there is adequate aeration, and observe the response of the prawns for at least 24 hours afterward.

Diseases

Diseases so far do not appear to be a significant problem in the production of freshwater prawns, but as densities are increased to improve production, disease problems are bound to become more prevalent. One disease you may encounter is "blackspot" or "shell disease," which is caused by bacteria that break down the outer skeleton. Usually it follows physical damage and can be avoided by careful handling. At other times, algae or insect eggs may be present on the shell. This condition is not a disease, but rather an indication of slow growth, and is eliminated when the prawn molts.

Harvesting

At the end of the grow-out season, prawns may be seine or drain harvested. For seining, depth (or water volume) should be decreased by one-half before seining. Alternatively, ponds could be drained into an interior large rectangular borrow pit (ditch) where prawns are concentrated before seining. You can effectively drain harvest only if ponds have a smooth bottom and a slope that will insure rapid and complete draining. During the complete drain-down harvest procedure, prawns generally are collected on the outside of the pond levee as they travel through the drain pipe into a collecting device. To avoid stress and possible mortality, provide sufficient aeration to the water in the collection device. Selective harvest of large prawns during a period of 4 to 6 weeks before final harvest is recommended to increase total production in the pond. Selective harvesting usually is performed with a 1- to 2-inch bar-mesh seine, allowing those that pass through the seine to remain in the pond and to continue to grow, while the larger prawns are removed. Selective harvest may also be accomplished with properly designed traps. Prawns can be trapped using an array of traditionally designed crawfish traps.

Polyculture and Intercropping

Culture of freshwater prawns in combination with fingerling catfish has been successfully demonstrated under small-scale, experimental conditions, and appears possible under commercial conditions. Selective harvest can help to extend the duration of the availability of the fresh or live prawn product to the market. However, there is a lack of research to show whether selective harvesting or a complete bulk harvest is the most economical approach.

Before introduction of catfish fry, stock juvenile prawns at a rate of 3,000 to 5,000 per acre. Stock catfish fry at a density to insure that they will pass through a 1-inch-mesh seine used to harvest the prawns at the end of the growing season. Although polyculture of prawns and a mixed population of channel catfish has been successfully demonstrated, logistical problems arising from efficient separation of the two crops is inherent in this management practice. Moreover, when harvest of prawns is imminent due to cold water temperatures, catfish may not be a harvestable crop due to an "off flavor" characteristic. Polyculture of channel catfish and freshwater prawns may be best achieved through cage culture of the fish.

Recently, a scheme for intercropping of freshwater prawns and red swamp crawfish was developed and evaluated (Figure 1). Intercropping is the culture of two species that are stocked at different times of the year with little, if any, overlap of their growth and harvest seasons. Intercropping provides for a number of benefits that include:

• Minimizing competition for resources;
• Avoiding potential problems of species separation during or after harvest; and
• Spreading fixed costs of a production unit (pond) throughout the calendar year.

Adult mature crawfish are stocked at a rate of 3,600 per acre in late June or early July. Juvenile prawns are stocked at a density of 16,000 per acre in late May and harvested from August through early October. In late February, seine harvest of the crawfish begins and continues through late June before stocking of new adult crawfish. Prawns are small enough to pass through the mesh of the seine used to harvest crawfish during the May-June overlap period.

Processing and Marketing

Production levels and harvesting practices should match marketing strategies. Without this approach, financial loss due to lack of adequate storage (holding) facilities or price change is inevitable. Marketing studies strongly suggest that a "heads off" product should be avoided and that a specific market niche for whole freshwater prawns needs to be identified and carefully developed.

To establish year-round distribution of this seasonal product, freezing, preferably individually quick frozen (IQF), would be an attractive form of processing. Block frozen is an alternative method of processing for long-term distribution. Recent research at the Mississippi Agriculture and Forestry Experiment Station suggests that adult freshwater prawns can be successfully live hauled for at least 24 hours, at a density of 0.5 pound per gallon, with little mortality and no observed effect on exterior quality of the product. Transport under these conditions requires good aeration. Distribution of prawns on "shelves" stacked vertically within the water column assists in avoiding mortality due to crowding and localized poor water quality. Use of holding water with a comparatively cool temperature (68 to 72 °F) minimized incidence of water quality problems and injury by reducing the activity level of the prawns.

Economic Feasibility

Based on a current feed cost of $250 to $300 per ton, a seedstock cost of $60 per 1,000 juveniles, a 2.5 to 1 feed conversion, expected mean yields of 1,000 pounds per acre, and a pond bank selling price of $4.25 per pound, the expected net return is $2,000 to $2,500 per acre. Revenue and ultimate profitability depend on the type of market that is used. This estimated return does not include labor costs or other costs. Some thorough economic evaluations that incorporate annual ownership and operating costs under different scenarios for a synthesized firm of 43 acres, having 10.25 acres of water surface in production, are provided in Mississippi Agriculture and Forestry Experiment Station Bulletin 985.

Table 1. Weight-dependent feeding rates for semi-intensive pond grow out of Macrobrachium rosenbergii.

Mean wet weight (g)	Daily feeding rate (% of body weight)
<5	0
5 to 15	7
15 to 25	5
>25	3
* As-fed weight of diet/wet biomass of prawns x 100

Figure 1.

A 24-month stocking and harvest scheme for intercropping freshwater prawns and crawfish. All years following year 2 will be the same as year 2.

Prawns

Year 1

• Stock -- May
• Harvest -- September through October

Year 2

• Stock -- May
• Harvest -- September through October

Crawfish

Year 1

• Stock -- mid-July

Year 2

• Harvest -- February through early July
• Stock -- mid-July

Source: University of Missouri - August 2003