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Hello friend of the farm today I am going to talk about how to raise shrimp and prawns in natural or semi-natural environments. This activity can be approached in various ways according to the level of investment you want to make and the knowledge you have of the species to be cultivated in terms of its biology, ecology, migrations, habits, etc. It is possible to complete the cycle in captivity; bring ovate females from the sea, raise larvae and fatten up commercial size; capture postlarvae and / or juveniles that approach the coast and fatten them.
Fish farmers have an option to earn good income in the breeding of freshwater prawns. Without limiting the coast, the practice in the ponds allows the fumigation activity to be fast, which reduces the logistics costs and get more competitive prices for the sales of the product in the local market.
Small producers with little experience can still benefit from the creation of what is a source of extra income. Dealing with freshwater prawns does not have many requirements and its management can be carried out in an unpretentious place, provided the conditions are appropriate, such as space for an aquatic environment and water temperature above 20 ° C for at least six consecutive months.
In captivity, it is common to use excavated ponds with a natural ground background, an area where the crayfish lives and also feeds. Without effective drainage system, dams and dams are discarded options, because they have to be emptied to make the total elimination of the shrimp and its withdrawal from all the shrimp at the end of the fattening period. However, if you do not have the property, the construction of the tanks should require a recovery of the capital invested in the long term.
A flat terrain with clay soil and water availability and quality are other important factors for the success of management. The breeding of these crustaceans also has a good adaptation to the integrated fish culture, the diversification of production and the increase of market opportunities.
Among the essential factors for freshwater shrimp farming, the water temperature and its quality, the topography, soil type, breeding, reproduction and other very important factors to be taken into account are highlighted.
Among the factors that are considered essential for the cultivation of shrimp in fresh water, there are the conditions of water temperature, good water availability, topographic location, type of soil and others. In addition to these technical requirements, the logistics situation should also be considered, such as: market studies, local infrastructure, access, manpower, among others.
Therefore, for the investment to succeed and prosper, the producer must take into account the following technical requirements:
CONDITIONS THAT THE AREA MUST MEET WHERE A FARM IS ESTABLISHED
It is necessary to have fresh and salt water, not polluted, the place should be easily accessible, be close to areas where gravid females can be obtained and, in the case of only fattening tasks, near the area where they can be obtained postlarvae or juveniles.
QUALITY OF THE SHRIMPS LARVAE TO RAISE.
Try to obtain larvae of very good quality, that are resistant to diseases and that in adulthood achieve a good size if it has been given the necessary food and care.
THE REPRODUCTION ALSO BEGINS IN SWEET WATER.
However, the larvae that are generated by the females must be kept in brackish water for 40 days until they undergo metamorphosis, which allows their release into freshwater ponds.
LOCAL TEMPERATURE.
The ambient temperature and sea water must be adequate for the growth of the species with which it is worked. In the case of tropical species, the temperature should not fall below 20 ° C, while for warm-water species, the range of water temperature may vary between 7 and 24 ° C.
The larvae process is technically complex and the temperature factor is directly connected. Therefore, it is recommended, above all, to carry out a study of local monthly temperatures, including the period of last year, so you can get two or three crops per year.
TOPOGRAPHY.
In terms of topography, the land with a gentle slope up to 2% is recommended, since they represent the largest economy in the construction of nurseries.
GROUND
The soil should be suitable for the construction of ponds and preferably not acid. The amount of rain and evaporation are data to be taken into account, since the two variables, in extreme cases, are important. Excessive evaporation will produce an increase in salinity that in values higher than 40 ‰ is generally detrimental and obviously a large amount of rain creates not only problems of low salinity, but also produces the overflow of the ponds, and rupture of walls which makes that operations should be suspended
The most usable soils are those with clay content between 30% and 70%. Very sandy soils provide excessive infiltration, making it difficult to keep the water in the ponds. Already the very clayey soils can create cracks that cause the water to drain in the parts of tracks.
THE PONDS
At present 2 types of ponds are used for fattening and raising shrimps:
Pre-nursery, versario, nursery: In general they are tanks of 1 or 2 hectares with a depth of 0.6 to 0.8 m; in them the shrimps are placed from the postlarvae or juvenile stages until reaching a weight between 0.5 and 4g according to the species.
Pond of fattening or hatchery: In them the shrimps are placed since they leave the nurseries until reaching the commercial size. Although in the first shrimp farms these ponds reached dimensions greater than 100 Ha, they are currently constructed with surfaces ranging from 5 to 20 hectares, which allows greater control of them.
FILLING THE PONDS
The water supply to the ponds can be made by difference of tides or by pumping. In any of the methods used, the existence of a reservoir is of fundamental importance. This is a channel whose bottom is built at a higher level than the bottom of the ponds, the walls have a height between 1.5 and 2.0 m, varying the width according to the flow of water you want, between 5 and 20 m. The walls of the reservoir are an integral part of the walls of the ponds, that is, the filling gates open on the walls of the canal.
The reservoir is usually filled by helical pumps 20 to 40 inches in diameter; It is convenient to have a battery of pumps.
The ponds should be fertilized between 7 and 10 days before the animals are placed. To carry out this operation, the organic and / or inorganic fertilizers are spread in suitable quantities (Appendix II) and then the filling of the ponds begins until the water column reaches 20 cm. In some cases it is recommended to bring the water level to 10/15 cm and after 5 days raise the water column to 30 cm (National Directorate of Aquaculture, Panama, 1984). Once the shrimp are placed, it is recommended to repeat this operation using half of the fertilizer quantities every 2-3 weeks.
The water that is placed in the ponds should be filtered, placing in the entrance hatch frames with filtering networks of a mesh size of approximately 0.54 mm mesh. It is also advisable to use a larger mesh that acts as a prefilter for the same purpose; In certain cases, it is convenient to build a mesh fence before the entrance hatch.
OBTAINING THE SEED
As it has been previously expressed, postlarvae and / or juveniles can be obtained either from natural environments or by spawning and development of eggs in eclosories. Until post-larval stages this method will be dealt with in a separate chapter, which is why we will only refer here to methods of capturing postlarvae and juveniles in the wild.
MAINTAINING THE PONDS
Once the shrimp are placed in the ponds and in order to maintain the medium in optimal conditions, water must be replaced. These changes can vary between 2, 5 and 25.0% as well as the frequency, which can be daily or every 3 or 4 days, this will be a function of the ability of the system to maintain water quality. Water will depend on the following parameters:
TEMPERATURE
It should be measured daily, for shrimp from tropical waters such as P.stylirostris, P.vannamei; the temperature of the water should be between 20 and 32 ° C, the optimum being between 22 and 30 ° C (Yoong Basurto and Reinoso Naranjo, 1982), although for P. stylirostris the best growths have been obtained at temperatures between 27 and 30 ° C being able to extend this temperature to all tropical species
SALINITY
This parameter should be taken daily and may range between 15 and 40% and for most species between 15 and 30%. In the case of Peneidos, which inhabit the Argentine coasts, salinity should not drop below 26%.
QUANTITY OF DISSOLVED OXYGEN
It is one of the most important parameters, it is quantified twice a day, in the morning and at dusk. In the ponds this element comes from the replacement water, the photosynthesis and to a lesser degree from the one that dissolves in the surface of the pond coming from the atmosphere. The lowest concentrations of oxygen are observed during the early morning and the highest at the last minute of the day.
PH
Indicates the concentration of hydrogen ions H +, that is, if the water is acidic or basic. The optimal pH range is between 7 and 9; but pH 5 values have been shown not to be harmful to shrimp. However, a pronounced rise or fall in pH values can have lethal effects on the ecological balance of the pond. The measurement of this parameter should be daily.
TURBIDITY
It gives an idea of the material in suspension that is in the water of the pond, this material interferes with the passage of light. In ponds should be avoided debris particles or clay in suspension. Turbidity is measured with the Secchi disk and is the measure of the depth at which this disc disappears when submerged in water.
If the visibility is less than 30 cm, there are potential problems, if it is greater the light can penetrate better and there will be a higher productivity and growth of the organisms from which the shrimp can feed. This measurement: it can be done every 3 days.
WATER COLORATION
It depends on several factors, concentration and type of algae, suspended matter, etc. The colors that water can present are:
Pale green: indicates adequate concentration of algae
Gray: denotes few algae in the pond, higher fertilization is recommended, complemented with water replacement
Green moss: algae that begin to die, an urgent water exchange is required.
Bright green: indicates high concentrations of algae, water should be exchanged to reduce the risk of lowering the dissolved oxygen concentration during the night.
Brown: indicates large amount of dead seaweed, water exchange and fertilization must be carried out, probably there is a lack of nutrients and excess metabolites.
FOOD IN THE DIFFERENT STAGES OF CRIA
In the diet we must take into account:
FOOD FREQUENCY
It is advisable to feed the animals twice a day, in the morning and in the afternoon, because if the ration is supplied in one opportunity, it will not be consumed immediately and therefore will begin to decompose, producing not only contamination but also a low concentration of dissolved oxygen, mainly at the bottom of the pond.
FOOD QUALITY
When the activities of shrimp farming began in the early days it was common to provide natural foods: for example, in the pre-harvests of Japan ground clam meat was used (Shigeno, 1975) to feed P. japonicus; while in the growth ponds the same author obtained good results with blue mussel and "short-necked clam", some varieties of crabs, euphausiids, anchovies, mackerel, etc. are also used and used. In the case of Argentine shrimp Artemesia longinaris, good growth is obtained by feeding on pieces of squid (López and Fenucci, 1987).
But natural foods present the problem of the difficulty of obtaining them, due to fluctuations, storage problems and variations in the price; that is why for several years now most of the research has been developed to try to obtain a pelletized, inexpensive food that allows a rapid growth of the shrimp in breeding, and thus find different pelleted or shaped products for sale. of lentil.
HARVEST
To perform this operation there are several methods: one is to gradually lower the water level of the ponds until you have a water column of 20-30 cm, then use different types of nets to capture the shrimp (cast nets, beach nets) .
Another method is to partially empty the pond to the same level, then completely empty it by placing networks or boxes at the exit of the gate, this is the method most used today. Care must be taken to lower the water level slowly to avoid strong currents that can crush the shrimp.
The harvest should be done between dusk and early morning at low temperatures and have ice available.
CONCLUSION
Recirculation and water change is only carried out recirculation of water in the egg, nauplius and mysis stages and from this last stage, a change that varies between 30 to a maximum of 80% daily. This operation is carried out to avoid contamination of the water by accumulation of ammonia wastes, special care must be taken to avoid abrupt variations in the temperature and salinity of the water in the tanks, since this can produce a high mortality.
SOURCE:
http://www.fao.org/docrep/field/003/AB466S/AB466S03.htm
http://www.fao.org/docrep/field/003/AB466S/AB466S04.htm
I hope that my article has served you well.
