Affordable, easy to manage fish cages with a production capacity of upto 312 fish per cubic meter made using bamboo, eucalyptus and low cost metal.

Raising fish in cages is a successful system used in many parts of the world. It has replaced the traditional fish-growing method of earth ponds. Its advantages are well recognized and it is widely spread all over the globe. The first and most important advantage is the unlimited amount of water surrounding the cages. This unlimited water supply provides vast amounts of oxygen and running water which is necessary for productive fish farming. Secondly, the financial investment in such a system is much lower. This system of cages is simpler in daily operation in comparison to any other commonly used method of growing fish.

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Large bodies of water tend to be better suited for cage culture than small ponds, because the water quality is generally more stable and less affected by fish waste. Exceptions are entropic waters rich in nutrients and organic matter. Small (1 to 5 acres) ponds can be used for cage culture, but provisions for water exchange or emergency aeration may be required. Cages should be placed where water currents are greatest, usually to the windward side. Calm, stagnant areas should be avoided. However, areas with rough water and strong currents also present problems. Cages may be moored individually or linked in groups to piers, rafts, or lines of heavy rope suspended across the water surface. At least 5 meters should separate each cage to optimize water quality. The cage floor should be a minimum of 4 meters above the bottom substrate, where waste accumulates and oxygen levels may be depressed. However, greater depths promote rapid growth and reduce the possibility of parasitism and disease.
The optimum fingerling size for stocking in final grow out cages is determined by the length of the growing season and the desired market size. The shorter the growing season, the larger the fingerlings must be at stocking. The use of male populations, which grow at 30-40% the rate of female populations, will result in larger fish, greater production and a reduction during the grow-out period. Recommended stocking rate of tilapia fingerlings depends on cage volume, desired harvest size and production level, and the length of the culture period. Water exchange is less frequent in large cages, and therefore the stocking rate must be reduced accordingly to fish size. In tropical or sub-tropical regions with a year-round growing season, a staggered production system could be used to facilitate marketing by ensuring regular harvests, e.g., weekly, biweekly, or monthly. The exact strategy will depend on the number of cages available and the total production potential of the body of water.
Fishes are cold-blooded animals and the temperature of the environment they are in directly affects all aspects of their biology. Each fish species has a range of temperatures in which it can live. When the temperature in the water reaches the upper or lower lethal limits it will kill the fish. If fish are subjected to extreme but not lethal temperatures for extended periods, their growth rates and other biological activities will be adversely affected and some are likely to die; either directly through malfunction of one or more physiological processes or indirectly (for example, through stress-induced disease and starvation). Within the tolerance range, each species of fish has a range of temperatures, which enable maximum growth (the optimum temperature range). At temperatures outside this range, feeding rates and the efficiency at which your fish convert the food they eat will be poor, resulting in slower growth and lower production. You will therefore need to site your fish farm in an area that has the optimum temperature regime for the fish species you intend to culture. Regions where lethal temperatures can be reached are therefore unsuitable for pond culture.
Water is the medium surrounding fish and the well being of your fish is dependent on the abundance and quality of the available water. A regular, abundant water supply is essential for the maintenance of a healthy fish stock. This applies particularly for those species that need flowing water with high oxygen levels (for example the salmonids). A reasonably abundant supply is also required for native fishes, particularly during spring and summer when water temperatures can exceed 30o C and poor water quality conditions can develop, necessitating a rapid exchange of water. If you are resident in a country that is prone to draught, you will need a way to guarantee the supply of water during drought periods, which can last for years in some countries. The quantity of water will determine the holding capacity and production potential of a facility. A supply of good quality water is also essential because poor water quality reduces fish survival and growth. The water supply must be relatively free of nutrients, sewage and other dissolved wastes, heavy metals, oils, pesticides, herbicides, chlorine, methane, hydrogen sulphide and other poisonous substances. Do not use water of extremely high turbidity (caused by silt and clay colloids) as it may stress fish, reducing growth and resistance to disease. Water quality variables need to be monitored regularly as they interact and can change from acceptable levels to lethal levels within several days, particularly during summer. You will need to monitor temperature, dissolved oxygen, pH and ammonia. Source water for fish farms can be drawn from many sources; for example runoff, rivers, creeks, impoundments, small dams, lakes, irrigation canals and underground (bore water). The type, size, location and topography of a farm will determine the best or most practical source of water. Bore water has a number of features that make it very suitable, particularly in intensive fish farming facilities.

The success of your fish farming business is dependent on many factors including the selection of a suitable site for your fish farm and the design and construction of facilities that enable efficient and economic operation.

A new technology to boost commercial fish farming in lakes, dams, reservoirs and rivers is being transferred from China to Uganda. The metal cage fish technology is being introduced by Chinese scientists through a three-year China-Uganda cooperation in aquaculture research, according to Barry Kamira, a research scientist at the National Fisheries Resources and Research Institute (NaFIRRI) and the coordinator of the project. The project started in April 2012.

Cage technology, unlike pond fish farming, relies on metal cages of various sizes that are suspended in a water body. Each cage carries up to 10,000 fingerlings. Fish farmers use a measure of their efficiency in converting food mass into increased body weight to know when to transfer the young fish to the next cage until they mature for harvesting six months later.

When the trial ends, the Ugandan government is expected to roll out the technology nationally. Uganda is taking the lead among the East African countries — Kenya and Tanzania to demonstrate the potential of rearing fish using metal cage fish farming technology to rapidly transform the sector from subsistence to commercial fish farming.