Basic Principles in Fish Farming
Modern fish farming started in Nigeria in 1964 when an officer was seconded from British Agriculture Department to initiate fisheries investigations. Fish farming is a very lucrative business, it however requires a lot of expertise for manipulation of the various activities. Fish farming procedures involves the following:
• Site selection
• Pond construction
• Liming
• Impoundment/flooding
• Fertilisation
• Stocking
• Feeding
• Water quality management
• Management of Health and diseases
• Harvesting the fish
1. Site Selection
Proper selection of site is probably the most important factor in the success of a fish farm. Site selection will depend on the kind of fish farm you plan to use. For pond construction, you need to consider the following factors: soil type, quality and quantity of the water available and the requirements for filling and drainage of the pond.
2. Pond Construction
The vast majority of freshwater fish are raised in ponds are usually located on land with a gentle slope. They are rectangular, circular or square shaped, have well finished dikes and bottom slopes. The pond should be drainable in case of harvesting of the fish.
Side slopes should be 2:1 or 3:1 which allow easy access will not encourage vegetation to grow and helps to reduce erosion problems. Depending on the site, fish pond could be: embankment ponds, excavated pond (diversion ponds) or Barrage ponds.
3. Liming
Liming of ponds after construction involves the addition of lime substances to pond bottom. The dosage varies depending on the lime type and pond conditions. Liming increases the pH of the pond.
Lime not only kills harmful animals and plants but also eliminates pathogenic bacteria. Liming also enhances the utilisation and release of certain nutrients from the pond bottom. Some of the commonly used limes include quick lime, slaked lime and agricultural lime.
4. Impoundment/Flooding
Impoundment/flooding is the introduction of water into pond prior to stocking. Water level should reach about 1.5 in a pond. It is important that sufficient water is available to fill all ponds within a reasonable period of time and to maintain the same pond level.
This water should be changed from time to time due to deterioration water quality parameters such as dissolved oxygen, carbon dioxide, Nitrite, Nitrate, NH3, turbidity, total alkalinity, and total hardness should be checked thorough before impounding.
5. Fertilisation
Fertilisation of pond is the addition of fertilisers in form of organic or inorganic into the fertilisation is aimed at developing natural food organisms and saving artificial feeds.
Fertilisation supplies the phytoplankton with the materials essential for photosynthesis. As the phytoplankton photosynthesise and reproduce, zooplankton, which feed on zooplankton, phytoplankton, and benthos also flourish.
Organic manures include animal faeces, urine of livestock poultry, night soil, green manure, compost etc. while organic manures often used in pond fertilisation include super phosphate etc. Application rate varies for each of the manure type.
6. Stocking
When selecting fish species suitable for farming, various biological and economic factors are important. These includes:
• Market price and demand for such fish
• The growth rate of such species of fish
• Ability of the fish to reproduce in captivity
• Simple culture of the young fish (Larvae or Fingerlings).
• Match between available fish feeds and the food preference of the selected fish species. Stocking density of fish varies from 3-8 fish 1m2. A farmer could either practice any farming method such as monoculture or polyculture.
7. Monoculture
Monoculture is the production of the same type of fish species on the some pond. In monoculture, only one species of fish is raised in the pond.
In monoculture, it is easier to give certain supplementary feeds to the fish as there is only one fish species. However, a single disease may kill all fish in the pond. Examples include Tilapia pond.
8. Polyculture
This refers to the production of more than on species of fish within an enclosure (pond/fish tank) during a particular production cycle. The increased production with polyculture as compared with monoculture is achieved by two effects: the better use of pond resources and the synergy between the two species such as tilapia and catfish.
In addition to better use of pond resources in the pond, the feed given as supplement is also better used: the Clarias, for example, mainly consume the fragments of rice husks, wheat bran and other similar feed ingredients while the tilapias filter suspended and floating particles.
By consuming tadpoles, frogs and wild fish, the Clarias eliminates the tilapia’ competitors. While on the other hand, the tilapias consume part of the floating vegetation of the pond.
Read Also: Problems of Post-Harvest Fish Activities and its Management Procedures
9. Feeding
There are 2 types of food in the pond which the fish can eat to grow: Naturally produced fish food inside the pond and supplemented fish food supplied from outside the pond to the fish. Natural foods include algae (phytoplankton) and tiny animals (zooplanktons).
Supplementary feeds are often formulated using a combination of the various feed ingredients, such as fishmeal, soybean etc. Feed ingredients are prepared, mixed and palletised into sizes and shapes require by the fish.
Fish should be fed 3-8 times daily with 3-5% of their body weight. Fish should be fed at the same time and in the same part of the pond.
Feeding should be done in the late morning and early afternoon when dissolved oxygen levels are high so fish have enough time to recover from the high oxygen-demanding feeding activity before nigh fall. Fish should not be over fed and feeding should stop at least one day before breeding, harvesting or transporting them.
10. Water Quality Management
Water quality is closely related to fish growth and yield. During production, water colour is the indicator of water quality, and there are various means of controlling water quality: feeding and manuring, use of aerators, adding fresh water, and turning the pond silt.
Water quality parameters such as dissolved oxygen, carbon dioxide, nitrate, ammonium nitrate, total alkalinity, total dissolved solids (TDS) should be monitored from time to time. This is because fish have optimum level of tolerance for each of these factors.
11. Management of Fish Health and Diseases
High and stable fish yields can be ensured through the daily routine of pond management, which should be performed carefully, diligently, and unremittingly throughout the rearing period. The principle of fish disease control is prophylaxis: “prevention is better than treatment” in the event of an outbreak of disease, fish should be treated in the early stages.
Because of complexity of their environment, fish are susceptible to viral, bacterial, fungal, and parasitic infections. An outbreak of disease jeopardizes regular aquaculture and threatens fish yields.
Therefore, controlling disease is one of the most vital tasks in fish culture. Good nutrition and proper water quality (with plenty of dissolved oxygen) are the most important factors for good fish health, needed to cope with diseases.
12. Harvesting the Fish
The final phase in fish farming cycle is the harvest and possible sale of the fish. When most of the fish are big enough to be eaten or sold, harvesting could either be total (capturing all the fish) or partial (capturing only the matured size).
Fish should not be fed at least a day before harvesting to prevent continuous digestion of food by fish which lead to excreation of waste.
Read Also: Management Strategies and Uses in Fisheries
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