Among favorable conditions the common carp could be propagated two-three times in a year in tropics and subtropics. As the experience shows the common carp spawns second time in January in the lake Alaotra (see APPENDIX No 5). It can be stated ; that the well being and appropriate keeping of the breeders is proved by that they become “ripe for propagation” in each 3–4 months.
The preconditions which are determining the sequences of the eggs' developments (toward the ripening stage) in the ovary are :
Temperature (should be 23–26 C°, the average daily water temperature).
Nutrition (should be suitable qualitatively and quantitatively, concerning especially animal protein, vitamine and mineral content).
Healthy, and appropriate keeping environment (especially avoiding crowdedness, shallow water, oxygen deficiency, and disturbances).
The fingerling producing capacity of the Andasibe Experimental Station would be enhanced greatly, if the second time propagation in January or February could be developed as a routine there.
It was hoped that the female breeders which already spawned (ovulated) in September among “normal” keeping and feeding conditions, practiced in Andasibe, become “ripe for propagation” in January. But the observations have shown in this current season, that the breeders ovary even did not reached the vitellogenesis stage (see APPENDIX No 1A.) up to that time. That means the usual keeping practice of the female breeders is unsuitable and fautly in Andasibe. First of all, the nutrition can be blamed because in the “H” ponds (1 are ponds) the bottom is bare clay, without livings, and the plancton is very poor, except red algae on the surface. Moreover the competing tilapias which penetrate quite freely in these ponds eat all edible. Therefore the role of natural food in the nutrition of the breeders is insignificant or even nil in these ponds. The artificial feed which was given perheaps quantitatively was enough, but its quality did not covered the necessary standard of full valued breeders' feed.
Observing that, the ovary development of the breeders ceased, or slowed down entirely. A supplementary feed of 0.5 kg dried shrimp and fish mixture was offered daily, one month long, minced into the normal feed ration of 2.5 kg (claimed having 20% protein content) for a group of 8 females totalling 27.3 kg (in the beginning of the trial, 3 females of high age died, the cause is unknown). It was hoped that this supplementary feed may restore the ovarial development of the eggs, and after one month they become “ripe for propagation”. (Besides the breeders, some 30 invaded tilapias of smaller size - 20–50 g. - was also in the same pond).
The observations on the breeders before and after the supplementary feeding further their artificial propagation trial, corroborate the following conclusions :
One month long supplementary feeding with high valued feed mixture is not enough to restore the ceased egg development. Only two breeders ovulated measurable quantity of eggs, 4 had produced only a few hundred of ovulated eggs, and 2 did not responded at all. The bulkyness of the abdomen could be seen on 1 fish, 2 more had a slight rounded abdomen, and 5 had totally flat ones. The other signs of the “readiness” for propagation were not definite.
The keeping conditions are not suitable for second time propagation in Andasibe.
Artificial feed available in the local market mixed with full valued ingredients (dried shrimp, blood meal, fish meal, etc…) and applying 2 months feeding time, may help to solve the second time propagation in the month of January or February.
Aiming the second time propagation of common carp in Andasibe, it is RECOMMENDED :
To stock breeders after the first artificial propagation for quick recovery into bigger well manured (free of tilapia and other fish) ponds (“C” or “D” ponds) in such density that each breeder should have some 40–50 m2 space. The recovery ponds have to be prepared on a planned way before, that a well developed natural food “await” for the breeders.
Protein rich extra feed should be offered from first days of November. For one female about 50 g. (½ kapoka) dried shrimp or fish minced with the normal feed may be enough. The daily ration of normal feed should be not more than 2.5% of the actual weight. It is supposed that in the pond they could find enough natural food as well.
The ponds in which the breeders are prepared for second time propagation, should be manured with pig, cow manure or compost in each fortnight (about 10–15 kg fresh manure per are).
