The fish are kept under a re-circulatory system, fed on 0.25 mm Skretting at an interval of 1 hour everyday, and the excess feed (if any) is siphoned out regularly. Average water temperature is 28 degrees centigrade .
What about the ammonia concentration in the water, if you are exchanging water regularly with the same water from other sources, then it is fine. But, i think may be the cannibalism, is a problem even though you give sufficient quantity feed, bcz during this stages they prefers natural food rather than formulated one. So, you may provide some artificial substrate and soil layer (mineralisation process( in the bottom to reduce the mortality.
I am also observed this type of situations among the farmers who cultured particularly Clarias batrachus, Anabas testuidineus etc... during their initial start of the rearing. But subsequently, they provide a layer of soil with water exchange, it was reduced significantly.
If three weeks old hatchlings of Clarias gariepinus is stocked for further growth then one of the reason of such mortality may be the presence of copepods which easily devour on hatchlings. So, first of all be sure whether the water in which the hatchlings are stocked are infested with parasitic copepods (temporary) or not. To confirm take a torchlight and inspect the system at midnight. Focus the light on water at the midnight. If you see copepods aggregating at the focus of light then it may be the reason of the hatchling mortality.
Alok Kumar Jena Rakesh Prasad Bhagat Thank you both for your insightful feedback.
I'll try them out to see which one works best in my situation.
1. The major cause of mortality even in catfish fry has been due to cannibalism. Its not just about the feeding frequency but the feeding quantity should be greatly considered. If the fish is not satisfied enough, they would prey on each other especially smaller and weaker ones.
2. The stocking density is also another factor. Higher stocking density induces higher mortality rate and vice versa
3. I hope water quality of total ammonia and nitrite level is ideal. This another cause of mortality
Such young frys of Clarias gariepinus are very sensitive to low temperatures, food scarcity, and parasites
Environmental factor and biological factor have affect on
three weeks old African Catfish
Major factors could environmental such as water quality parameters (pH, ammonia and temperature) and biological such as feed and feeding practices
All above mentioned comments are a possible cause. It is important that recommended levels are followed. Remember around that age, maybe a little sooner, the African catfish are developing their breathing organs which can be a very stressful time due to the high rate of development, this can cause moralities if any additional stress is placed on them. At this period you may also be weaning them from Artemia to a formulated diet which can cause additional stress. What i would recommend in terms of feeding routine is to use live artemia for the first couple days of exogenous feeding so the fish can get valuable enzymes from the live feed, then move to decapsulated artermia cysts mixed with important supplements like vitamin C and spiralina. I would remain on the decapsulated cysts until they have move passed this period of expected high mortalities, and then slowly wean them onto a commercial feed still including important supplements. I have also seen that over feeding during this time can cause RIS so try stay within recommended feeding rates. Make sure they are not exposed to excessive lighting 24hours of darkness is preferred. Hope this helps, you and anyone else.
Vincent Oduor you are welcome. If you do end up using the Feeding routine suggested and notice any results please let me know.
@Mark Joscelyne definitely, I will let you know if I observe any significant changes.
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