Written by Aquaculturist Jackson Siame Fish farming can be practiced in different ways, namely pond culture, cage culture, raceway (flow-through) culture and tank (recirculation aquaculture system) culture.

In Zambia, pond culture is the most practiced system. Pond culture is simply the rearing of fish in a pond.

Site selection

Firstly a site with a moderate slope is selected on a given piece of land. Soil from the same site is then sampled to determine its water holding capacity. An earthen pond can be constructed on soil with a good water holding capacity. In an event were the soil is unable to hold water, a pond liner can be used.

Pond excavation

A pond can be excavated manually or using an excavator. An ideal pond should be 1,1 m on the shallow side and 1,3 m on the deeper end. Dykes must be well designed and strong enough for their purpose. The inlet pipe/canal should be placed slightly higher over a shallow part to create a fall as the water fills the pond. This will increase the dissolved oxygen in the water. The outlet pipe must be strategically positioned for easy draining and flushing of the pond.

Lime

Agricultural lime can be sprinkled in a pond at a rate of 15 kg/100 m². It is necessary to add lime in an earthen pond right at the beginning of the culture. However, ponds lined with pond liners may only be required to be limed at the second culturing cycle and onwards.

Manure

Once the pond is constructed, it can be filled with water up to a depth of 60 cm, and chicken or pig manure can be added at a rate of 8 kg per 100 m². Put the manure into a bag with small holes for gradual release. Once the water turns green, the pond can be filled to a depth of 100 cm.

Stocking

The recommended time to stock the fish is in the morning when the temperature is low. Stocking ratios to be used ranges from two to five fish/m², when the average body weight is expected to be between 800 g and 1 000 g. Six to ten fish can be added when the desired average body weight is between 300 g and 400 g. A pond of 10 m x 10 m has a total area of 100 m² and can accommodate a total number of 600 fish at a stocking rate of six fish/m² (10 m x 10 m = 100 m², 100 m² x 6 fish). The higher the stocking ratio, the more frequently you need to flush the pond. Aeration is the other alternative to flushing. Once the fish is stocked, you can proceed with the feeding, which should commence two days after stocking.

Next month we shall look at feeding schedules, pond sampling and pond management.

For any further queries or clarifications, please contact the writer directly, who happens to be the Savanna Streams Limited Aquaculturist based at the Livestock Services Centre, in the Lusaka Show Grounds. Contact him on: +26 (0)97 1570 980 or info@essentialcom.biz