Changes were introduced in the techniques of artificial propagation of common carp based on the latest practical research in this field, changes which make artificial propagation easier and more efficient. The timetable of propagation was changed according to the local possibilities and work schedule in Perinet:
First day: capture and culling of the breeders. They are kept in the cement concrete tanks more than half a day. It often happened in October that the females broadcasted their eggs without any treatment, due to the advanced ripeness caused by adequate feeding of the breeders.
Second day: at 05.00–06.00 h first injection (10% of the final doses). The same day at 17.00–18.00 h, stitching the females and second injection (3–3.5 mg/kg).
Third day: at 06.00–07.00 h stripping and egg treatment. This working schedule enables the worker to carry out the propagation programme in the daylight. During night time the water temperature is fairly stable so the ovulation time can be easily predicted.
The hypophysis injection was administered for both female and male breeders into the peritoneum under the pectoral fin. This system has the following advantages:
the administering of the injection is very easy;
no massage of the injected place is necessary (as it is if the injection is made into the muscle);
the hormone solution never flows back as often happens when administered into the dorsal muscle.
The stitching of the females has also been made simpler and safer. Two cross stitches are made between the anus and genital opening and between the genital opening and urinary duct respectively. The closing of the genital opening in this way is easy and sure.
The technique developed by K.W. Chow (1982)1 of administering the first feed (full egg diet) to the larvae in the rearing jars in the form of microcapsules was also introduced. It proved better than the previous system which comprised only the yolk of hard boiled eggs.
The mass transport of the developing eggs of common carp was again tested. (The packing and transport technique is described in Woynarovich, 19802.)
There was a great improvement in egg production following the proposal for keeping and feeding the breeders out of the propagation season which made it possible to propagate the common carp for a four-month period (September-January). Some of the breeders (females) propagated in December had previously propagated in September.
The survival rate of the common carp larvae was very poor in some nursery ponds due to the intrusion of small blackbass fingerlings from the reservoirs via feeding canals (in that season the propagation of the blackbass stock in the reservoirs of the Perinet Station was very good.) To avoid such losses in the future a box-filter mechanism was suggested and placed under the inflow water where all the weed fishes were killed. Sometimes 5–25 dead fish were collected from one box. Now all nursery ponds of the station are equipped with such a filter.
Three groups of silver carp breeders were propagated by 16 December. Approximately one and a half million fertilized eggs were obtained (the “dry” weight of the eggs was 1 650 g). Further propagation was suspended (although there were about 10 ripe females and males for propagation) due to the lack of nursery facilities. Having one million eggs at one propagation also created a problem because there were not enough incubation jars for such a large quantity of eggs.
Because of the lack of nursery facilities in Perinet, ⅔-day old larvae were transported to Kianjasoa (5 000), Sissaony (5 000 + later 70 000) and Analabe (10 000). They were transported partly without oxygen in plastic bags and partly under oxygen pressure in plastic bags. Ten-day-old fry were collected in the nursery ponds of Perinet Station with a short fine mesh net and transported in plastic bags under oxygen pressure to Sissaony (20 000), Analabe (7 000), Ambatofotsy (5 000) and Manjakatompo (5 000); 15-day-old fry was transported to two small lakes near Ambatundrazaka (8 000). The reservoirs of the Perinet Station also were stocked; 5 000 in the smaller one and 7 000 in the bigger one.
The transport of the young silver carps was necessary because the keeping facilities in Perinet are very limited.
Three-month-old silver carp fingerlings were introduced in Madagascar on an experimental basis in September 1978. They were stocked at the Kianjasoa experimental station. They became sexually mature in October 1980; their propagation failed. One female and two males were still alive on 27 November 1981. This female was ripe for induced propagation. (The same female was not ready for propagation on 16 October 1981 when hormone-treated.)
The second experimental introduction was made on 4 October 1979. A total of 124 3-month-old silver carp, 10 2-month-old bighead carp and 47 2-month-old grass carp were sent to Madagascar. More than 50 specimens of silver carp remained alive on 10 October 1981. These fishes became ripe for propagation on 28 November 1981 at the Perinet Station. They reached sexual maturity in Perinet at an age of 2 years 4 months.
The grass carps were not ripe; only a few males showed sexual maturity in November 1981. The propagation, attempted again in the first days of 1982, was not successful.
The few surviving bighead carps were totally unripe sexually. Their maturity can be expected in November and December 1983.
Other bighead and grass carp together with improved Hungarian common carps were introduced in October 1981 (100, 100, 100 specimens). They were stocked in Kianjasoa (30, 30, 30) and at the Perinet Station. The survivors were 45 bighead, 55 grass carp and 42 common carp until 1 December 1981.
A manual was compiled by the consultant on the basis of his experiences, and local possibilities and practices applied in Perinet. The manual was designed to facilitate the future propagation of these commercially very important fishes. The text and drawings are attached to this report as Appendix 1.
Three persons were appointed for training from the Fisheries Section of the Direction des Eaux et Forêts. One person also from Fisheries Research (FOFIFA) participated. Moreover, the station manager of Perinet and his deputy took part in the practical training.
The programme conducted on the artificial propagation of common carp comprised 4 batches of breeders (4–6 females and 2–3 males in each batch). Emphasis was placed on the preparation and calculation of the hormone doses, new techniques of stitching the females and administering the injection in the peritoneum under the pectoral fin. The manager of Perinet Station with his assistants carried out 4 artificial propagations of common carp without any aid from the consultant, according to the established timetable.
Training in the artificial propagation of silver carp and handling of the breeders was also given to the same personnel on three occasions. They were trained in the general propagation practices and also in the identification of the ripe sexes, tranquillizing of the silver carp and grass carp with Chinaldin (Quinaldin), the fertilization, handling and incubation of eggs, preparation of nursery ponds, larvae rearing and feeding. The transport of larvae, collection of 10/15-day-old fry, conditioning, packing and transport of the fry were also covered.
The question of shortrange transport of the breeders within the Station also had to be solved. A very suitable type of satchel was made from locally-available plastic-coated waterproof material. The dimensions and manufacture of the satchel are explained in Appendix 1. One person in Perinet was trained in the making of the satchels.
The consultant spent some time at the Kianjasoa Experimental Station. Here he again studied, inter alia, the extension possibilities of fishculture by constructing reservoir ponds in the flat valleys of the area. These reservoir ponds would serve three basic aims: (a) flood control during heavy rainy periods, (b) water storage for the dry season (c) fish production at little cost.
The latter will be very effective for the polyculture of Chinese major carps and common carp. The main species woule be silver carp and bighead; second, grass carp; and third, common carp and Tilapia (Sarotherodon) nilotica.
The structure of the reservoir ponds should be standardized: 40–50 cm wide monks for draining, simple but wide with stone-enforced spillways cut into the hillside. As the reservoirs would cover a maximum of 5 ha, the oversized structures constructed on the existing reservoirs are not necessary. Reservoirs built in rows would provide very effective flood control. The reservoirs would be drained and cropped during the dry season in August and September.
With the introduction and successful propagation of silver carp, fish culture could gain a new perspective in the country. Silver carp needs no artificial feed to produce a high yield. The freshwaters in Madagascar are generally rather poor in plant nutrients (phosphorous and nitrogen compounds) and most of them have a low pH due to the organic (humic) matters originating from the disintegration of tree leaves (Eucalyptus).
To achieve adequate yields from fish ponds with silver carp (main fish), bighead, common carp, tilapia, grass carp (as supplementary fishes), organic manure is necessary. The cheapest and most economic way to provide organic manure is the joint rearing of ducks, pigs or poultry with fish.
To encourage such development the consultant compiled a short manual on fish-cum-duck culture based on his experiences in Hungary and in tropical areas. The manual is attached to this report as Appendix 2.
