The Andasibe Experimental Station will be developed as a fish propagation and training centre, when the middle scale hatchery becomes established. It should be used for desmonstration purposes as well.
The consultant spent during his recent appointment 54 days in Andasibe. While observing the fishery activity, and management, he could state the follows :
Most of the ponds are not exploited well for the planned fish culture.
Many ponds were stocked with common carp (breeder recruitment, or for growing market size) and Tilapia, aiming polyculture. But the Tilapia overpopulated the mentioned ponds soon, and the carp stock due to the lack of food did not grow or even grow thinner. In such “polyculture” there is a hard competition effected by the thousands of different size tilapias.
Bigger ponds (1000 m2) are used for raising Tilapia and crucian carp (Carassius sp) ; therefore in the propagation season there is a lack of nursery ponds.
The present keeping of the carp breeders is by far inadequate. So they do not develope as much eggs (100,000–200,000/kg per propagation) as they are due, to according to their fertility. The quality of the eggs also is not satisfactory (see II. chapter).
Many ponds are overgrown partially or totally, with unwanted water weeds, which decrease greatly their fish productivity potential.
The water feeding system of the station is full of tilapia fingerlings. They have quite free entry in each pond. Even in the nursery ponds could be found bigger tilapia and Gambusia.
Most of the ponds, especially the breeders and recruitment ponds, were not manured since long.
The animal manure (pig, cow, poultry) supply of the station is too complicated and very expensive.
The bottom of the ponds is not ploughed or turned over time to time (yearly or in each two years) so it is exhausted already. There is hardly to find a bottom layer rich in organic matters.
The cropping of the young fingerlings is too rough. High percentage of the fingerlings is perishing or becomes severely injured during the cropping.
The station acts as a fish refuge, holding many fish species without the appropriate keeping (feeding, propagation, etc…). There are many Tilapia species and hybrids of unknown parents, Crucian carp, golden Gambusia, Black bass, Heterotis niloticus, Paratilapia, etc…
The station is often endangered during the cyclon time by inundation.
To improve and stabilise the fish production in the station the following measures are RECOMMENDED :
A. GENERAL AND BASIC REQUIREMENTS.
It has to be cared that the wild tilapia fingerlings could not invade freely into the ponds. Therefore stable fish traps (made of wire mesh) should be installed in suitable places of the main feeding canal (where barrages are built in), which will catch all the small fish which enters from the reservoirs.
When necessary, the tilapia and other fish should systematically eradicated from the feeding canal system. Filterboxes have to be used to prevent wild fish invasion.
It should be strictly prohibited for the workers of the station, to introduce arbitrarily tilapia into any of the ponds.
Planned fish culture can start then in the station, when it is freed from wild fish invasion.
It has to be decided “which fish” will be cultured in the station. The consultant opinion is : there is no use to keep black bass if they are not provided day by day with living animals (fish, frogs, insects). The black bass which are kept in the “C” 1 pond are meager, ever hungry ; their propagation is unsuccessful.
There are different species of Tilapia and their hybrids : it should be selected one or two species which is most suitable for farming, and only those should be kept in stock for propagation fingerling and market fish production.
It has to be decided whether crucian carp fingerling production should be made or not. If yes, improved technology (induced spawning by hormone injection, controlled spawning on kakabans in small ponds) has to be applied. For this purpose, small ponds have to be used, and not the biggest as now. The consultant opinion is that the demand for crucian carp fingerlings, which is not an object of the up-to-date fish culture, is so little, that the quantity requested can be produced elswhere nearer to the Capital.
It is meaningless to keep Heterotis niloticus in the station which is not an object of planned fish culture.
B. IMPROVEMENT OF THE MANAGEMENT.
It is RECOMMENDED :
To arrange the year in three production periods ;
Each pond should be cropped, at least on the end of the period and restocked according to the production plan. (This system is applied in tropics and subtropics to get the highest yield from the advanced fish culture.)
A production plan has to be worked out determining the level of fingerling - market fish - breeder recruitment-production in the different ponds.
B.1. Common carp propagation management
a) The main propagation season of common carp is in September and October. 10 (5 + 5) females can be propagated in each week. Nursing season will last up to end of November. If the keeping conditions will be improved, a second propagation will be possible in January and February. November and December will be the propagation season of the Chinese major carps.
The “A” ponds (1 are each) have to be reserved for nursery purposes. One nursing time should not last longer than 21–28 days. In one pond, when it is prepared properly, 15.000 just feeding fry can be stocked. Here 50% survival rate can be expected. “A” ponds can be used 2 may be 3 times for nursery purposes in each propagation season.
The “B” ponds 1, 2, 4, 5, 7, 8, 9 should be reserved for nursery purposes and for keeping the fingerlings after the nursing time up to the transport. 100.000 just feeding fry can be stocked in a “B” pond (10 ares).
The remaining “B” ponds 3–6 will be used raising the Chinese major carps and common carp recruitment in polyculture. The “B” 10, 11, 12, 13, 14 can be used for crucian carp propagation, if necessary, further to keep male carps and recruitment.
b) Special attention has to be paid for keeping the female common carp breeders out of the propagation season. It is basically wrong to keep the female breeders in small confinement (1 are) throughout the year as now. Here they can not regenerate quick after the propagation and can not develope their eggs.
It is recommended to keep 60 females breeders and 20 selected recruitments which can be also propagated. The same number of males should be kept as well.
After the propagation, the females have to be stocked in well prepared bigger ponds, as the “D” 1, 2, 3 (10 females per pond) ; the rest should be stocked in the “C” ponds where 5 females can be stocked per pond. (In general for 1 kg female 10 m2 pond surface is calculated ; for 1 kg male 5 m2 only). The ponds “D” 4, 5 further the “B” 10, 11, 12, 13, 14 can be used for carp males according to the need.
The female breeders should be cropped, checked and weighed between 10 and 20 August. They should be groupped according to the similar weight, in 5 members groups (it easies the propagation) and transferred into the “H” ponds (segregation ponds) where they should remain up to the propagation. The “H” ponds have to be prepared two weeks earlier for receiving the females (20 kg fresh manure or compost, 0.5 kg superphosphate and 0.5 kg Nitrogen fertilizer per pond) and cleaned from all grass and weed.
The female carp breeders should be stocked in monoculture, strictly without tilapia. When Chinese carps will be available, they can be kept with the breeders in polyculture ; with 5 breeders, 2–3 grass carp and 3–4 silver or bighead carp can be stocked. The grass carp should be fed here daily with cut grass as usual (continuous manuring effect).
The manuring of the breeders' ponds (“D” and “C” ponds) should be made if possible, in each fortnight with compost (20 kg per are) or fresh pig or cow manure (10 kg per are) or poultry manure (5 kg per are).
Concerning feeding of the breeders in out-of-season time, it is recommended a scanty feeding 1.5–2.5% of body weight per day (about 20% protein content). It is supposed that they can find enough natural food. Exceptions are those groups which are prepared for January-February propagation. They should be fed according the recommendation in chapter III.
The artificial feed has to be given in one place marked with a pole in each breeders' pond. The fish will accustome to find the feed there (to avoid feed losses and washing-off-s). (For young fish and for tilapia, the feed should be distributed along the shore).
B.2. Planned Tilapia propagation/management
The number of Tilapia breeders has to be determined according to the market demand for fingerlings + the fingerling provision to the station.
The selected Tilapia pairs should be propagated in small ponds which were constructed for this purpose. The “F” and “G” ponds can be used for that. When 1 batch of offspring grown up enough big for netting with small mesh net (0.3–0.5 cm mesh), they should be removed by netting out, and stocked with other batches into “E” ponds, up to the transport, or stocking in production pond.
B.3. Fish growing (market fish production) management
a) Practically the “A” and “B” ponds are free from December for fish growing purposes. That means in two production period (see point B/1) (each last 4 months long) plenty of market fish can be produced. Stocking rate should be 10–20 carps fingerlings per are. Mixed culture (this is not polyculture because the carp, crucian carp and Tilapia compete with each other for food) can be practiced here stocking 20–50 young Tilapia with the carp fingerling per are.
The feeding of the fish can be made with cheap ricebran or similar cheap feed. The manuring and fertilising of the ponds will be beneficial for the crop.
When it is stated that the Tilapia stock achieved the sexual maturity and they start to proliferate, the pond has to be cropped without delay. When the Tilapia start to propagate there, no more carp growth can be expected. Therefore it is totally wrong to stock in “polyculture” with the carps, sexually ripe Tilapia breeders, hoping that they will create there a suitable stock.
b) All “A” and “B” ponds have to be emptied during August and they should be prepared for nursery purposes (if possible turning over or ploughing the bottom and manuring).
B.4. Miscellaneous recommendations
a) It is recommended to investigate the flood situation in the station. When it is found out from where is coming the dangerous water amount, measures should be made accordingly. If it comes from the reservoirs, suitable size water escape ways have to be installed. Or if it is coming from the river, the river bed should be cleaned from the hindrances (logs, fallen-in-trees) providing quick flow off the water, further constructing higher dams on the endangered reach and/or establishing screens at the end of the outflow canals, to prevent fish escape.
b) It should be endeavoured to increase the pig and if possible the cattle stock in the station, to get cheap manure for the ponds.
c) It would be advisable to plough the ponds or overturn their bottom, once in each year. Turning the soil is important especially in the nursery ponds, and can be connected with manuring (using for example compost). By this way, the enrichment of the soil in organic matters can be achieved. Bigger ponds can be ploughed with bullocks (they produce valuable manure as well) or using small garden ploughing machine.
d) All out grass which is not used for feeding the grass carps should be composted to have cheap manuring material.
e) The small ponds have to be drained rather often. Their draining and closing the monk afterward is rather complicated. It is recommended to build in the monks turning pipes (made of 3"–4" plastic pipes) which enables the quick and simple draining, and there is no need to close the monk with packed mud.
f) Parallely with that, the possibility of application of fish catching boxes (cropping boxes) should be investigated, and make changes in the draining canals accordingly. For example, building in the draining canal, cropping pits out of bricks or cement concrete for fixing the catching boxes.
g) The two reservoirs which supply the station with ample water could be utilised for extensive fish culture. Stocking the reservoirs with common carp (1000–2000 in each reservoir) selected Tilapia breeders (50 pairs), later with silver and bighead carps (1000–2000 per reservoir) a good crop can be achieved. Here would be place for keeping black bass stock (50–100 per reservoir). Each reservoir should be harvested and restocked in each alternate year. From the reservoirs healthy breeder recruitment can be selected, as well as hypophysis donors.
