Production System

AQUACULTURE PRODUCTION SYSTEMS

Agriculture is multi-functional. Fish farming easily compliments other existing agricultural activities, both crop and livestock production, including irrigation activities. Fish are very easy animals to rear. They can convert feed into body tissue more efficiently than most farm animals, transforming about 70 percent of their feed into flesh. Fish also have excellent dress-out qualities, providing an average of 60 percent body weight as marketable product and a greater proportion of edible, lean tissue than most livestock. Fish can be intensively cultured in relatively small amounts of water with overwhelming success.

The success of any production system for any specie is highly dependent upon maintaining good water quality. This is accomplished by adequate and reliable aeration, oxygen¬ation, and frequent or continuous water exchange to renew dissolved oxygen (DO) content and remove waste products. Fish farming systems that discard water after use are called flow-through systems, while those that filter and recycle water are called recirculating aquaculture sys¬tems (RAS), recycling or water re-use systems. Each type has its own advantages and disadvantages.

1. Pond Production Systems

ponds

Ponds (earthen or concrete) are the most extensive fish farming technology being used across the world and have been in use dating back to time immemorial. The Bible refers to fish ponds and sluices (Isaiah, Chapter 19, verse 10), and Hieroglyphics illustrate that the Egyptians of the Middle Kingdom (2052-1786 B.C.) developed ornamental fish ponds and attempted intensive fish culturing. Research indicates that the Roman's were quite adept in raising fish in ponds and also cultivated oysters. The Hawaiian people are said to have practiced aquaculture by constructing fish ponds; an example from ancient Hawaii is a pond at Alekoko dating back at least 1000 years.


A lot of research information and commercial experience in design, construction, investment requirements and operational management exists for a variety of culture species including food, bait and ornamental fish, crustaceans and aquatic plants. Ponds also offer flexibility of use such as nursery and grow out phases of production, water storage and effluent treatment and for recreation.


Aquatic plant production is often overlooked in the aquaculture community, yet is a significant commodity that has higher prospects for growth.
Challenges of pond culture of food, bait and ornamental species include competition from other countries which affects market prices especially for food species; increased regulatory concern of fed pond culture increase operational costs; predation remains a significant factor for ornamental and bait production; pond culture is land intensive and requires a lot of space which means more cost for the investor; limited growth rates in regions with lower temperatures especially for the tilapia breams.
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2. Cage Culture

What is Cage Culture?
Cage culture is an aquaculture production system where fish are held in floating net pens within a water body. Cages are widely used in commercial aquaculture overseas and individual cage units come in all shapes and sizes and can be tailored to suit individual farmer’s needs. Cage units can be purchased through commercial outlets, but can also be made from readily available construction materials such as polypipe, wood, bamboo or steel. Cages can be used in both freshwater and marine environments.
Advantages of Cage Culture
> Use existing water bodies.
> Technical simplicity with which farms can be established or expanded.
> Lower capital cost compared with land-based farms.
> Easier stock management and monitoring compared with pond culture.
Disadvantages of Cage Culture
> Stock is vulnerable to external water quality problems e.g. Algal blooms, low oxygen.
> Stock is more vulnerable to fish eating predators such as water rats and birds.
> Growth rates are significantly influenced by ambient water temperatures.
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3. Closed or Recirculation Aquaculture Systems (RAS)

Closed or Recirculation Aquaculture System (RAS) is one which re-uses water with mechanical and biological treatment between each use. Most systems use tanks for growing the fish, with water being recirculated through various media that act as filters (mechanical or bio-filtration) and pumped back into the tank. Adequate aeration is a major pre-requisite for all RAS operations to allow for an intensive practice. A Recirculation Aquaculture System usually occupies a very small area, requires less water than conventional aquaculture, allows for higher stocking densities and provides a predictable and constant environment for the culture species. 

RAS can be done in either tanks or ponds. Tanks are usually designed specifically for this purpose and are constructed from food grade plastic or fibreglass. Some may be constructed from concrete or glass. Tank recirculation systems are commonly used in hatcheries and for the production of ornamental fish as large quantities of fish can be grown in a relatively small area of tanks. 

Circulating water in ponds is an effective tool in destratification that improves oxygen levels throughout the pond and increases microbial oxidation of organic matter. Pond recirculation system technology is relatively new with many potential designs. Key to the systems is mechanical water circulation (pumps, aerators, or circulators) within a pond or pond/raceway combination. 

Advantages of using the RAS include reduced water use and production effluent; improved water quality; easier accessibility to fish from raceways; increase in species diversity and increased sustainability 

Disadvantages of these systems include the constant need to pump or mechanically move water; higher fish production costs compared to open pond culture; due to increased pumping costs; unproven economic feasibility in some cases specific design criteria will vary depending on individual site; production objectives and regulatory requirements. Farmers should carefully consider the costs and benefits prior to developing a pond recirculation system. 
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4. Flow-through Tank Systems

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Flow-through tank systems depend on constant or periodic water ex¬change to flush out fish waste prod¬ucts. Exchange rates are determined by the available water quality and quantity, the fish biomass, and feed¬ing rates. As a rule, the volume of wa¬ter needed for a facility is the amount required to replace 100 percent of the tank water every 90 to 120 minutes. Flow-through systems often are not suitable for commercial tilapia tank culture. Tilapias are a warm water fish species that grow best when the water temperature is approximately 25 to 29 °C. Unless incoming water is from a geothermal source or is warmed, it will be too cool for optimum growth. Warming large volumes of incoming water is generally not economically feasible. Operations with a constant source of heated water, such as a geothermal or low-cost waste heat source, might be economically viable. 
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5. Fish Farm Tank Designs

Tanks for culturing tilapia can be of different sizes and shapes as long as they allow for the effective removal of waste solids. Tilapias produce a solid waste that is well-suited for removal from culture tanks. When fed com¬mercial fish feeds, they produce fecal strings held together in a mucous membrane that maintains the feces in a relatively large, filterable size. The longer these solids remain in the tank, the smaller they become (as they disintegrate) and the more waste am¬monia they generate, so tanks should be designed for the rapid and efficient removal of waste solids. If tilapia fecal material is not quickly removed from the tank, the mucous membrane will trap gases generated by bacterial decay and cause the fecal string to float. For this reason, some tanks have an additional sur¬face drain at the center (standpipe) or on the tank sidewall to remove surface water and floating solids. Research has shown that round or octagonal tanks with flat bottoms have better solids removal than those with sloped or cone-shaped bottoms. The slope may prevent solids from moving to the center drain. Tanks with flat bottoms also are simpler and less costly to build. 
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6. Greenhouse Aquaculture

With the rapid growth and development of the aquaculture sector world-wide, researchers and engineers are developing more and more complicated production specific technologies that are expensive to set up. These technologies are coming in various forms, chief among them being the greenhouse aquaculture production systems. This latest technology can make use of small pieces of land for intensive fish farming with the size of a mere 50m x 15m being capable of producing up to 200tonnes of fish per annum. Production equipment constitutes a huge chunk of the initial capital investment while feed will consist up to 70% of the total operational expenditure. This type of production is most ideal for urban commercial/industrial aquaculture where markets are close and a reliable supply of power (electricity and fuel) for aeration and pumping demands. 
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7. Aquaponics

Aquaponics is the systematic and symbiotic cultivation of plants and aquatic livestock in a water recirculation environment or set up.

Aquatic animal effluent (for example fish waste) accumulates in water as a by-product of keeping them in a closed system or tank as in a Recirculation Aquaculture System (RAS). The effluent-rich water becomes high in plant nutrients but this is correspondingly toxic to the aquatic animal.

Plants are grown in a manner that enables them to utilize the nutrient-rich water, i.e. on floating beds or along the sideways of the tank or pond. The plants’ uptake of the nutrients reduces or eliminates the water's toxicity for the aquatic animal.

The water, now clean, is returned to the aquatic animal environment and the cycle continues. Aquaponic systems do not discharge or exchange water. The systems rely on the natural relationship between the aquatic animals and the plants to maintain the environment. Water is only added to replace water loss from absorption by the plants or evaporation into the air.

Aquaponic systems vary in size from small indoor units to large commercial units. They can use fresh or salt water depending on the type of aquatic animal and vegetation. Aquaponic systems can be used to replicate controlled wetland conditions that are useful for reclaiming potable water from typical household sewage, in addition to generating a continual supply of food with minimal fertilizer use. Aquaponics takes advantage of synergy between self-organizing biological systems, emphasizing the one element/many functions principle of permaculture as a natural solution for water treatment.
Advantages of using Aquaponic Systems
The unique advantages of aquaponic systems are: 

1. Conservation through constant water reuse and recycling.
2. Organic fertilization of plants with natural fish emulsion. 
3. The elimination of solid waste disposal from intensive aquaculture.
4. The reduction of needed cropland to produce like crops. 
5. The overall reduction of environmental footprint for crop production.
6. Small efficient commercial installations can be built close to markets therefore reducing food miles.
Disadvantages
Some conceivable disadvantages with aquaponics are:

1. Initial expense for housing, tank, plumbing, pump/s, and grow beds. 
2. The infinite number of ways in which a system can be configured lends itself to equally varying results, conflicting     research, and successes or failures. 
3. Some Aquaponic installations rely heavily on man-made energy, technology solutions, and environmental control to     achieve recirculation and water/ambient temperatures but a system designed with energy conservation in mind (such as     utilizing solar heating and the exploitation of gravity to reduce pumping) can be extremely energy efficient. 
4. Whilst careful design can minimize the risk, Aquaponics systems can have multiple 'single points of failure' where     problems such as an electrical failure or pipe blockage can lead to a complete loss of fish stock. 
5. Like all aquaculture based systems, stock feed usually consists of fish meal derived from lower value species. Ongoing     depletion of wild fish stocks makes this practice unsustainable. There are now, however, organic fish feeds available     which may prove to be a viable alternative and negate this concern.