1.1 Aquaculture Production Systems
- Extensive systems
- Semi-intensive systems
- Intensive systems
Aquaculture, compared to crop and animal farming, is much more diverse and varied. There are many different species that are cultured each with different ecological requirements. They therefore have different feeding and breeding requirements as well as water quality. Production systems have therefore been developed to meet both the economic needs of the producer and the requirements of the species to be cultured.
Depending on the planned level of production and the resources available, the producer will make a choice from the following:
i). Extensive systems
In these systems little or no input is used in the production. Fish are stocked in cages, still water earthen ponds and other water impoundments (for example reservoirs) and left to fend for themselves. Low stocking densities and thus low yields characterize the systems. The main cultured species are Tilapines (e.g. Oreochromis niloticus), catfish e.g. Clarias gariepinus and Cyprinus carpio. These are low input-low-output production systems. Majority of the small scale, subsistence fish farmers in rural Kenya fall in this category. Production in these systems ranges between 500 and 1500 Kg/Ha/year.
i). Semi-intensive systems:
These systems form the bulk of aquaculture production in Kenya. In these systems still water earthen ponds and cages are used as holding units for fish culture. Still water pond culture uses the natural productivity of the water to sustain the species under culture. However to enhance productivity, the ponds are fertilized using both chemical and organic fertilizers at varying proportions to enhance natural productivity. Exogenous feeding using cereals bran and other locally available feeds is done to supplement pond productivity. Polyculture of Oreochromis niloticus, Clarias gariepinus and Cyprinus carpio is practiced with various combinations of species.
Commercial production in these systems range between 1 - 3 Kg/m2/year depending on individual farmers management level. Some farmers in western Kenya have achieved production levels of between 6-10Kgs/m2/year with tilapia and catfish.
ii). Intensive systems:
In these systems water flows in and out continuously (flow through). This allows higher stocking densities. The systems require good supply of good quality water. Less land is required to produce the same quantity of fish as compared to extensive and semi intensive systems.
The systems employ mainly raceways, various types of tanks and floating cages as holding units. In these systems, more fish are produced per unit area by complementing or substituting the natural productivity in the culture units by exogenous feeding using complete feeds (the feeds are specifically manufactured for the species under culture) and water aeration. Such operations require high initial capital investment and high operational cost. They are mainly suited for high value fish like the Rainbow trout.
Production in such systems in Kenya range from 10 to 70 Kg/m2/year. This depends on the management levels employed by individual producers. This production can go higher with better management and quality feeds.
1.1 Issues to consider for pond culture of fish:
a) Fish to be produced
Different fish require different ecological conditions and production techniques to grow.
The choice of what to produce will therefore be guided by:
a) Market preference
b) Ecological requirements of the fish
c) Production technology of the fish
d) Resources available to produce the fish
b) Proposed farm site:
Fish farming is a long term investment and therefore it is important to know land tenure system of the site. Conflicts may arise regarding land ownership.
The topography of the land will determine whether it will be possible to construct fish production facilities and also the cost of construction. The accessibility of the site throughout the production period is very important. Availability of power and other essential infrastructure should also be considered. The location of the site in relation to the market is also important.
Fish are aquatic animals. Enough clean water is required throughout the growing period. Will the water be enough to last the entire growing period? Is it of good quality? Water quality refers to consideration for salinity, temperature, dissolve oxygen, acidity/alkalinity (pH) suspended particulate matter. Water that is good for livestock and human beings is good for fish farming. It must not contain excessive dissolved and suspended solids or toxic substances.
Where earth ponds will be used to grow fish, soils with good water retention ability are preferred. Where the soils are too porous, then the option of using pond liners or tanks can be considered. Note that this will increase the investment cost. Some soils are acidic and this needs to be corrected through liming. Lime may not be cheap.
It is good to know the source of good quality fish seeds (fingerlings). Some stunted or sick fish may be sold as fingerlings. The bad quality fish cannot grow to acceptable market sizes and may not even be acceptable in the markets. Sourcing fingerlings from certified sources is important.
b) Fish feeds:
Fish feeds come in various forms e.g. powder, pellets, marsh or granules. Commonly used feed ingredients include maize bran, rice bran wheat bran, fresh water shrimps etc. Farmers should always consult fish feeds experts for correct information.
Availability of quality fish feeds is critical to the success of the enterprise. Feeds form the highest single cost entity in fish farming - up to 60% of the enterprise operational costs are incurred on feeds. Feed requirements in fish vary with age. Young or juvenile fish require a higher protein content feed (about 35% - 40%) while adult fish may require 25% - 35% protein rich foods.