Category Archives: Shrimp

Shrimp Farming Systems

Shrimp Farming Systems

There are three different farming methods used for Macrobrachium rosenbergii, the most commonly farmed variety of shrimp.

Extensive Freshwater Shrimp Culture

Extensive freshwater shrimp culture generally involves growing in ponds. There is little or no control over water quality. The growth of shrimps is not normally monitored, supplemental feeding is not supplied. It reflects the most natural and least scientific or industrial production of freshwater shrimps. Shrimp productivity is in the about of 500kg/ha/yr.

Semi-Intensive Freshwater Shrimp Culture

Semi-intensive shrimp farming systems involve stocking juvenile freshwater prawns in ponds, and result in a range of productivity of more than 500 kg/ha/yr. External fertilisation is applied and a balanced feed is ensured. Shrimp predators and competitors are controlled and water quality, shrimp quality and shrimp growth rate are monitored.

Intensive Freshwater Shrimp Culture

Intensive shrimp farming may take place both outdoors or indoors. Intensive culture refers to freshwater shrimp farming in small earth or concrete ponds. High water exchange and continuous aeration enable stocking at greater density than and achieving an output of more than 5000 kg/ha/yr. Generally construction and maintenance costs are high and require continous supervision which includes satisfying a nutritional requirements, the elimination of predators, and strict control over all aspects of water quality.

Freshwater Shrimp Farming Guide

Shrimp Farm Water Quality Management

Shrimp Farm Water Quality Management

Managing water quality is of utmost importance in shrimp farming operations. Good water quality ensures proper growth of shrimp and reduces mortality. Various water quality parameters such as salinity, hardness, temperature, dissolved oxygen levels, nitrite levels among others need to be adhered to for ensuring optimum production. It may be sound complicated however it is pretty easy to monitor these parameters using easily available test strips.

Dissolved oxygen

The optimum dissolved oxygen content of pond waters is about of 5 mgllitre. Aeration is a proven technique for improving dissolved oxygen availability in ponds. Various types of aerators are used for pond aeration. In heavily aerated ponds strong water currents can cause erosion of pond bottom. Therefore, placement of aerators in a pond should be considered carefully.

Often people include plants in the pond to keep the pond well-oxygenated. It should however be kept in mind that though they may release large amount of oxygen but in night they tend to taken all the oxygen which may cause fluctuation in oxygen levels. In warm weather the problem may get worse as warm water generally tends to have less oxygen.

The following steps help to alleviate the problem:

– Enhancing water circulation by using aerators.

– Reducing the stocking level.

– Removing the silt from the bottom of the pond as the bacteria that grow there consume a lot of oxygen thereby depleting dissolved oxygen levels so necessary for the shrimp population to thrive.

Temperature

Temperature determines the rate of shrimp growth. Water temperature can be adjusted to optimum levels in indoor shrimp hatcheries. It is difficult to adjust water temperature in large water-bodies. Aerators not only help in improving oxygen levels but also help in maintaining uniform temperature.

Turbidity

Turbidity results from several factors including suspended soil particles, planktonic organisms and through decomposition of organic matter. Turbidity resulting from plankton is generally desirable. However, excessive turbidity prevent heat and light penetration adversely affecting shrimp growth.

pH

pH is a measure of hydrogen ion concentration in water and indicates how acidic or alkaline is the water. The pH of water affects the metabolism and physiological processes of shrimps. pH also exerts considerable influence on toxicity of ammonia and hydrogen-sulphide as well as solubility of nutrients.

Total hardness

Hardness is an important factor for fresh water fish ponds. It should be ideally be greater than 40 mgllitre. Hardness helps to protect shrimps against harmful effects of pH fluctuation and metal ions. Ponds with relatively low hardness can be treated with lime to increase hardness.



Pond Pumps and Filters

Pond Pumps and Filters

How to Select Pond Pumps

Pumps are very important in shrimp farming or for that in any fish farming operation. It would possibly not be wrong to say it is the most integral and vital piece of equipment in all recirculating aquaculture systems.

Pumps are essentially of two types : submersible and external pumps. The selection of the most appropriate pump depends on the size and scale of your shrimp farming operations. Generally submersible pond pumps can be installed very easily. However as regards efficiency external pumps score better than submersible pumps.

The most important factors when it comes to choosing pumps are their power consumption measured in watts and pumping capacity measured in gallons per hour. The initial cost depends greatly on these two factors. However it is important to keep in mind that greater efficiency is likely to result in power saving over a period of time. In order to achieve truly energy efficient operations it is good idea to go in for solar powered pumps either at the very outset and as early as possible in shrimp farming operations.

How to Select Pond Filters

Pond filters also comprise an important component especially in indoor shrimp farming operations. The functions of a filter are two fold: one is the removal of solid waste by process of mechanical filtration, and secondly biological filtration. A filtration system must be able to handle both requirements. Some filtration systems combine both mechanical and biological filters into a single system while in others the filtration occurs as a part of a two step process.

When choosing a filter it is important to remember that it is only one part of the system. The scale and size of the operations help to choose a filter.



Pond Aerator Systems

Pond Aerator Systems

Selecting Pond Aeration systems

Pond aerators are used to increase the level of dissolved oxygen in water. Water aerators are used to combat low oxygen conditions in lakes and ponds or in aquaculture tanks. Dissolved oxygen is a major indicator of water quality and a vital parameter in maintaining optimum productivity in shrimp and other fish farms. Grossly reduced oxygen levels may result in mass morbidity of aquatic life.

There are two common techniques to aerate a water body : surface aeration technique and subsurface aeration technique.

Natural Aeration

Natural Aeration results in surface as well as subsurface aeration techniques.

Surface aeration results from disturbance of the surface of water because of falling water such as from a falls, fountain or stream.

Sub surface aeration primarily occur via aquatic plants. Aquatic plants release oxygen into the water via the process of photosynthesis and thus support aquatic life.

Surface Aeration

Surface aeration is achieved via fountains, floating surface aerators and paddle wheel aerators.

Fountains help to enhance the aesthetic appeal of water bodies. However they are not so effective in increasing dissolved oxygen of a large water body in an appreciable manner.

Floating surface aerators work in a manner similar to fountains. Their ability to enhance oxygen levels are also limited. Further they do not enhance the appeal of water bodies as fountains do.

Paddle wheel aerators are most effective in increasing dissolved oxygen levels and as such they find maximum use in shrimp and other aquaculture operations.
They are powered by electric motors and mounted on floats. They are mostly used in outdoor shrimp farming.

Subsurface aeration

Subsurface aeration is achieved by means of diffused aerator systems. Diffused aerators utilise bubbles to oxygenate water. Bubbles are released at the bottom of the water body. As the bubbles rise to the top, aeration of the water body takes place.

Diffused aerators are classified into two types depending on the natures of bubbles they produce : course bubble generators and fine bubble generators.

Course bubble generators are generally much more inefficient in enhancing oxygen levels because of larger size of bubbles generated.

Fine bubble generators are extremely effective in enhancing oxygen levels. However one difficulty with fine bubble generators is that the diffusers may clog and therefore they need to be cleaned periodically to ensure their effectiveness. The problem is more in case the turbidity of the water is high. Fine bubble generators are frequently used in indoor shrimp farming.

Diffused aerators of various capacity depending on requirement may easily be obtained from Amazon.



Tilapia and Shrimp Polyculture

Tilapia and Shrimp Polyculture

Shrimp and tilapia aquaculture individually have proven to be very profitable in the last couple of decades, the prime reason being increasing demand all the time. So from the demand perspective, these businesses are immune to downside risks. However, being a biological produce there is always a risk, howsoever minimal of climatic, bacterial or viral factors affecting production.

Current shrimp farming practices are based on use of large and shallow ponds, with very low water circulation per day and no aeration, to raise a single shrimp crop. Shrimps dwell and crawl on the bottom of the ponds. As a result, the water volume remains largely unoccupied.

It is here that tilapia can be introduced and integrated into shrimp aquaculture. Tilapia can be introduced into the shrimp aquaculture system in two ways:

Shrimp and Tilapia simultaneous polyculture

Tilapia can be raised simultaneously with shrimp in the same pond. Each variety occupies a different teritorial niche within the same pond. Tilapia grows in the upper part of water while shrimps dwell at the bottom of the pond. The relationship between shrimp and tilapia is not competitive on feed and territory, but symbiotic. Tilapia feed on phytoplankton and zooplankton while shrimps on the bottom substrate. It is seen that introducing tilapia in shrimp ponds enhances shrimp growth.

Tilapia assists shrimp production by improving and stabilizing the water quality, cleaning the pond bottom and by having a probiotic type effect in the pond environment. Tilapia can reduce excessive phytoplankton biomass in later stages of pond culture and recycle nutrients effectively.

Shrimp and Tilapia polyculture by crop rotation

Shrimp and tilapia crop rotation can be practiced with an objective to minimise the possibility of viral epidemic in case of shrimp monoculture, thereby greatly eliminating risk of loss in production. In case of tilapia, they are largely resistant to viral epidemics.
Thus risk to business may be reduced while increasingly the chances of consistently higher production.

Raising Freshwater Shrimp

Raising Freshwater Shrimp – Spawning and Larval Rearing of Shrimps

Mating in shrimps take place immediately after premating moult in matured female.Spawning occurs a few hours after mating. The incubation period of eggs lasts between 10-14 days depending upon the water temperature. The optimal water temperature being 25-35°C. At lower temperatures, the incubation period tales longer is stretching to more than 21 days. Hatching takes place due to body stretching of the zoea, which breaks the eggshell and comes out from the egg and starts swimming.

Different larval rearing technologies such as static, clear, green water, closed or semi-closed, with or without circulation systems are practiced. The green water technique is generally reported to increase the post-larval production by 10-20°C over other techniques. But higher mortalities are encountered because of rise in pH and greater algal bloom. Also, there is enhanced increase in numbers of adult artemia, due to abundance of feed in green water, contributing to accumulation of ammonia in the culture medium. The production of post-larvae in large numbers is possible following bio-filter re-circulatory systems. The larvae passes through eleven zoeal stages before attaining post larval stage within a period of 45-60 days at salinity and temperature ranging from 18-24°C and 25-35°C, respectively.

Bio-filters equipped with re-circulation capability have shown encouraging results in maintaining favorable water quality in different rearing media with enhanced rate of post-larval production.The most important parameters of the rearing medium include temperature, pH, dissolved oxygen, total hardness, total alkalinity, salinity and ammonical nitrogen. These influence greatly the growth and survival of larvae in captive rearing. The respective parameters within the ranges of 25-35°C, 7.8-8.2, 3000-4500 ppm, 80-150 ppm, 18-20°C and 0.02-0.15 ppm are considered optimal during the larval rearing of shrimps.

Raising Freshwater Shrimps – Harvesting and Rearing of Post-larvae Shrimps

Harvesting of post-larvae of shrimps is slightly difficult due to their crawling habit. Therefore, siphoning of water are commonly used for harvesting. However due to longer duration for attaining post-larval stage the above method is not very safe because of possible deto-riation in water quality. Also, the presence of post-larvae in the larval tank affects the growth and survival of advanced larvae due to competition for food. Therefore there is a need for an suitable device for regular harvest of post-larvae from the rearing unit. A method called string shell has been devised and is being successfully used for phasewise harvesting of post-larvae during larval rearing.Post-larval survival and production rates, following bio-filter re-circulatory system, are in the range of 10-20 PL/l.

Optimum growth, production and survival of shrimps can be achieved in grow-out ponds on stocking with nursery reared juveniles rather than by stocking directly with the fresh post-larvae. The post-larvae slowly adopt themselves to the freshwater. It is observed that generally optimum growth and survival of healthy juveniles during post-larval rearing is achieved at salinity of around 10‰.

Post-larval rearing of shrimps can be done both in well-prepared earthen ponds with adequate aeration facility and in indoor hatchery following bio-filter re-circulatory system. Stocking density, feed and water quality management play the major role in raising healthy juveniles during rearing. Optimum stocking density is between 10-15 post-larvae/l. Water quality has to be continously monitored to ensure that all parameters are within desirable limits.

Raising Freshwater Shrimps – Growout Culture of Shrimps

Growout culture of shrimps is similar to that of other freshwater fishes. To prevent shrimps from migrating from one pond to another, it is necessary to have the pond embankment at least 0.5m to 1m higher from the water level. A sandy clay pond bottom is is well suited for better growth. A stocking density of 30,000 to 50,000/ha is maintained for semi-intensive farming. Intensive freshwater shrimp farming with stocking density upto to 1 lakh/ha is possible in ponds with adequate aeration and recirculation capabilty. Water temperature is the single most important factor which directly affects the growth and survival of prawns. Temperatures above 40°C or below 14°C are generally not conducive to shrimp growth. On the other hand temperatures between 22-33°C is optimal.

Males grow faster than females. A production of 500-1200 kg/ha in six months of rearing are achieved under shrimp monoculture with the stocking density of 30,000-50,000. In case of shrimp polyculture, at a stocking density of 10,000-20,000/ha along with carps at density of 2,500-3,500 nos/ha, a production of 300-400 kg prawn and 2000-3000 kg carps or tilapia can also be raised. A discussed in a previous post, freshwater shrimp farming in conjunction with tilapia is therefore always preferable.

Freshwater Shrimp Farming Guide

Shrimp Broodstock Management

Shrimp Broodstock Management

Shrimp broodstock management is essential for continuous operation for seed production. The maturation of the species differs greatly depending on the location and climatic conditions. Under pond conditions, maturity of shrimps generally occur after attaining a maximum size of 60-75 mm. Berried females are recorded year-round in some of the ponds. The ratio of berried females in total population is found to be higher during rainy months and during this period they carry good quantity of eggs (10000-80,000). Shrimps breed 3-4 times in a season. Successful community breeding and year-round seed production of shrimps under captive conditions is possible.

Since the juvenile seed requirement for commercial farming is not met from the natural resources, large-scale seed production under controlled conditions for year-round supply is extremely important. The technologies of large-scale seed production and grow-out culture have led to increased attention of the farmers and entrepreneurs for diversification of their culture practice.

Incubation period of eggs lasts between 10-15 days depending upon the optimum water temperature of 28-30°C. However, at lower temperature, the incubation period is longer. Different larval rearing technologies such as static, flow-through, clear or green water, closed or semi-closed, with or without circulation systems of larval rearing of shrimps under hatchery conditions have been developed. The green water technique generally provides higher sucess over other techniques.Bio-filter systems equipped with air-lift re-circulation has shown promising results in maintaining favorable water quality in different rearing media with enhanced rate of post-larval production.