Monday, 03 October 2011 16:25
Most of the diseases among human beings are influenced by their dirty environment and caused by the food they eat.
These diseases can be cured thru the application of appropriate medicines and by observing cleanliness and sanitation.
But in the case of prawns, when attacked by a disease, there is no medicine that can cure or treat it.
The disease or virus comes from their dirty dwelling place. Prawns are bottom dwellers and they submerge their whole body in the mud. When the mud is polluted or dirty, it produces bacteria that attack the prawns like the “white spot virus”.
Let us go back to basics.
What are the causes of pollution in the fishpond?
1. Pollution is caused by rotten mud that is under stagnant water for a longer period of time;
2. Pollution is caused by the absence of water change which causes shortage of dissolved oxygen in the water that kills the prawns and fish;
3. Pollution is aggravated by the application of fertilizers and feeds when the pond bottom is dirty.
when the pond bottom is polluted bacteria thrives and attacked the prawns living in a dirty environment.
What are the counter-measures to prevent pollution?
1. Dry up you fishpond for one (1) month every after harvest to recondition the pond bottom and to kill the bacteria and to release obnoxious substance from the soil; (Drying up of the pond bottom can be reduced to 15 or 20 days during dry season and if the fishpond is not polluted).
2. Flush out the dirty water after harvest before drying the pond bottom;
3. Flush out again with water after sun drying to remove the remaining obnoxious substance and apply tea-seed to kill the unwanted fish or a combination of lime and ammonium sulfate (1part ammonium sulfate and two parts lime) in shallow water;
4. Don’t use chemicals to poison the fish bristan, thiodan, malathion and other pesticides that will cause pollution and kill microorganisms in the pond; Continious use of chemicals pesticides will destroy and pollute the pond bottom that will adversely affect production.
5. Provide 2 gates for each pond if necessary in order to have separate entry and exit points to prevent pollution by changing water one month after stocking. Water change could be done at least 3 times every high tide and two thirds (2/3) of the water in the fishpond is replaced after high tide.
Cautions:-1. When the prawns are attacked by white spot virus, harvest the stocks and dry up the fishpond to cure pollution;
2. when there is insufficiency of dissolved oxygen and the prawns float in the morning change water if possible and if not harvest the stocks if the harvestable size and change stocks after proper pond preparation to prevent more losses.
(The author engaged in extensive prawn farming for 30 years and the aforementioned observation are based on actual experience. Others may have different way of improving fish production based on their personal observation).
By Rex Miravite
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