THE POND BOTTOM AND ABILITY TO DRAIN
The pond bottom should be smooth and firm. Pot-holes at the bottom
provide shelter for fish to hide after ponds have been drained. Such fish, if
not removed, will predate upon the new stocks, Survival rates for the new cycle
will subsequently be lower with few very large shooters. The pot-holes also
pose a danger to persons seining the pond who may trip and injure themselves.
If the bottom is not firm, fish can hide in the mud. Thick layers of pond
bottom mud not only have a negative effect on the pond productivity, but are
also more difficult to seine. At drainage, a lot of fish also get trapped
within the mud. Sampling and harvesting is therefore, more difficult and
time-consuming in such ponds. It should be possible to completely drain and dry
the pond bottom, after harvests and between cycles. This helps to ensure that
all fish have harvested. Being able to drain ponds completely in between cycles
makes it easier to undertake routine treatments and required maintenance work
with better results. Preferably, ponds should be able to fill and drain
completely by gravity to avoid pumping water, which is costly. Therefore, a
pond bottom slope of 1-2% to the outlet is recommended. Ponds and drainage
canals should also be constructed above the water table. Ponds constructed
below or at the level of water table, are impossible to drain and dry
completely. In addition, yields and returns from such ponds are poorer, because
of the constant infiltration of cold, non-oxygenated sometimes acid water from
water table into the pond during the course of production. Consequently, the
quality of water within the pond becomes less suitable for production.
NOTE: All it
takes is one catfish left in the
mud, and the next round of fingerlings stocked in the pond after re-filling
will be eaten by the remaining large catfish survival rate of the following
cycle will be extremely low.
HARVEST
BASINS
Having a harvest basin set in the
pond or between ponds is optional but recommended. Harvest basins make it
possible to hold and handle fish alive while draining ponds. They also reduce
the amount of labour required during complete pond harvests. A harvest basin
can either be set within out outside the pond. Ponds that are to be drained
frequently, for example nursery ponds, are much easier to harvest if they have
a properly constructed harvest basin.
SHAPE
OF POND AND ITS ACCESSIBILTY
Typically, ponds are rectangular.
Rectangular ponds are more practical construct, feed and manage. The narrower
pond dimension dictates the size of the seine that will be needed. Therefore if
one has ponds of several sizes on the farm, it is good idea to have them of
similar widths, if possible so that the same seine can be used for all ponds.
All ponds on the farm should b e easily
accessible for adding inputs and transporting harvested fish from the pond with
relative ease and safety.
OTHER
STEPS INVOLVED IN PREPARING POND FOR STOCKING
Pond preparation for stocking marks
the beginning of the ‘grow-out’ production cycle. Before the pond is socked for
production, it should be prepared in the following way:
REMOVE EXCESSIVE SILT FROM POND BOTTOM
The bottom of the pond bottom should
be free of excessive amount of suit. It should also be dry and firm before
filling. Silt removed should NOT be
put at the top of the pond levee (as this increase the free board), but rather
away from the ponds and / or used to repair the pond levee slopes. Remember, much of the bottom “silt” came
from the slope of the leaves. It should, therefore, be put back form where
it came. If the soil is heaped on top of the dykes, it will wash back into the
pond when it rains. Because the bottom silt often contains high levels of
nutrients, e.g. from leftover feed (if the person is a bad feeder) and feces,
it is sometimes used to fertilize vegetable gardens. However, unless the feed
input was excessive, the amount of nutrients in the silt is often not enough to
justify the labor that is required to move the silt to a garden.
When soil builds up on the bottom of
the pond, the pond becomes shallower. Over time, the bottom mud lowers water
quality for production. This is of particular problem when a farmer over feeds
the fish, which can often occur when sinking feed is being used. After several seasons of mud build-up in
the pond, the pond’s yield and carrying capacity for the new cycle will,
therefore, be lower than that of the previous cycles. If there is no so much
silt, the bottom can be left to dry until the surface cracks slightly before
the pond is re-filled with water for the next cycle. The cracks allow air to
enter between the mud and aerate it. Alternatively, the soil can be disked to
aerate and increase the rate of decay of organic matter which in turn, reduces
the rate of formation of substances such as hydrogen sulphide.
4.3.2 ENSURE THE POND IS NOT LEAKING
Repair all broken dam levees and make
sure there is no seepage through the pond levees or around inlets or outlets.
CALL 08032861326 FOR HELP AND CONSULTANCY.
CALL 08032861326 FOR HELP AND CONSULTANCY.
