Until the expert's arrival the ponds at the fish farms were, for the most part, excavated and undrainable, or in such a condition that they could not be kept dry or prepared for the spawning season. Since such ponds could not generally produce a sufficient number of healthy fry necessary for the development of fish culture, it was recommended that all ponds be built in future with gravity discharge in order to permit the bottoms to be dried out as required.
To improve the operation of ponds, arrangements were made to reduce excavation. Dykes were constructed with slopes ranging from 1.5:1 to 3:1, and - depending on the type of soil - a core trench provided and necessary allowance made for shrinkage. The inlets and outlets were constructed first so that they could be used while the dykes and other structures were being built. Provision was made for a cropping channel of appropriate size and depth.
Routine examinations of water and soil conditions were made. These included measurement of pH, acid combining capacity (ACC), plankton, water temperature, determinations of the suitability of the earth for bund building and the level of the water table.
One of the expert's first tasks was to develop proper installations in the fish farms and provide suitable implements. During his visits, it soon became apparent that some essential equipment was lacking, and that some already in use needed improvement. He consequently designed or redesigned many items, including those listed below.
Draw-nets. A proper fish-farm draw-net was introduced, and simple light nets which would minimize damage to the fish were made to replace previously used heavy ones;
Hand-nets or scoops. A hand-net of circular, triangular or semicircular frame of iron or wood, with a bag of fine-mesh twine, was designed for use for the first time;
Hammocks. Canvas sacks (“hammocks”) mounted on a wood frame, which can be carried by two people, were constructed to transfer adult breeders or fry from pond to pond with the minimum amount of injury to the fish;
Metal drums. Metal containers from empty cement drums were prepared for weighing fish or carrying fry. These drums can be cut easily so that they weigh 4.5 kg (10 lb) for use in weighing fish;
Grading table. A grading table was designed which rested on two 1 000-litre vats. The same table, if padded with straw and covered with sacking material, can serve as a suitable receptacle in the selection of spawners;
Gallows for steelyard and recording table. This set-up was improvised to serve as an efficient system for measuring and weighing fish produced during harvest time;
Punt. Two punts of a design suitable for fish farms were constructed: one built for the Parwanipur fish farm, with the help of local carpenters and another for the Pokhara fish farm by the Balaju Kastha Karyalaya Company. The type used before the arrival of the expert was a dugout which was unsatisfactory for fish pond work. 1
Implements for sampling fish and checking their food consumption.
Fish samples were collected with a cast-net. Checks on the
consumption of supplementary food supplied to the fish were done
using a scoop specially designed for use in the fish farms.
When the expert arrived in Nepal in late July 1963, the ponds at the Godawari fish farm were being completed and work had just begun on their outlets. He found that the type of outlet structure planned was far too expensive and so he designed another type which cost much less. These were installed and are now operating very satisfactorily.
The water intake system had also been started with the use of many metres of concrete pipes made locally. The expert redesigned some of the intake systems to provide a better water supply, and also designed control inlets, which were cast in situ.
The concrete pipes that were used were not smooth on the inside and thus would be a constant source of trouble through clogging. The expert recommends that in future work, open channels be used in place of pipes. Open channels are cheaper to construct and safer to use in that they seldom clog, and even if they should clog, they are easy to clean. Where it was deemed necessary to use piping, it was recommended that asbestos-cement pipes be used. These are cheaper than concrete, the pipes are smooth inside and are simple to lay and seal.
The slopes of the pond bunds were also too steep and work was begun to correct and improve their slopes.
Unfortunately, most of the Godawari ponds were of the excavated type and many had springs which made draining them and drying the bottoms difficult. This condition was not conducive to the proper spawning of carp or the good health of fish being reared.
At the time of the expert's arrival, common carp (Cyprinus carpio) of the mirror variety imported from Israel, and scaled and mirror varieties imported from India, were in the ponds. The spawners selected from the very young and small mirror carp and the best of the scaled carp had already spawned, but due to a heavy infestation of parasites only about 50 percent of the spawn had survived.
The ponds were treated with unslaked lime before the next spawning season. It was believed that such treatment would exterminate the parasites dwelling in the moist pond bottom. However, this treatment did not completely eradicate the pests, probably because the ponds had not been completely dried.
It was recommended that new breeding ponds be constructed on the right bank of the brook to provide ponds which could be completely dried out following breeding and thus prevent much of the disease that usually occurs in continually wet ponds. A tendency existed at Godawari for the public to consider the farm as a recreation centre and to keep them from interfering with the fish stock, the ponds had to be constantly filled with water. This is not a satisfactory situation for a carp fry hatchery. Further-more, fry storage ponds should be kept dry for at least one month prior to use. The pond bottom should be treated with unslaked lime and the pond filled just before use to control diseases and prevent the development of insect larvae and other animals which feed upon the fry.
A special pond was constructed for conducting experiments with asla (Oreinus molesworthii). Asla is a common local species and it was desirable to determine if it could be raised easily in ponds. The experiments showed that although it could be bred in ponds it was very slow-growing and thus was of no commercial value. In a six months' trial culture, it grew 2.5 cm (1 in.) in length and approximately 15 g (½ oz) in weight.
The expert tested the water for pH, acid combining capacity (A C C), plankton and temperature at various times. The water at Godawari remained cold most of the year and thus the fish in this farm would have slower growth than those in farms with warmer water. If the ponds could be dried out when required and disinfected properly and used only for spawning and storing of brood stock, a healthy and vigorous stock of fry could be produced each year. The fry produced could then be transferred to warmer areas for rearing.
In 1965, the expert recommended improvements of the ponds at Parwanipur and most of these were carried out. New type outlet drains were also installed in ponds which could be drained by gravity. Unfortunately, as at Godawari, some ponds in Parwanipur could not be completely drained and this presented similar difficulties in fish raising.
Two new ponds were built according to the expert's designs, and these were being used as segregation ponds for breeders. The 1964 spawning season produced a large number of fry, but the final cropping was very small. As the expert was not present at the time of the cropping he was unable to determine the cause of the losses. It was suspected, however, that an infestation of parasites similar to that which occured at Godawari might have been the cause. If that were the case, liming and drying of the ponds before the spawning season should improve the situation.
The water supply to the farm was very irregular owing to demands for irrigation. To become a fully successful farm, an adequate water supply should be maintained in the future.
On the occasion of his first visit to the Janakpur farm, 20 ponds had just been completed. The expert observed that as these ponds had been constructed by excavation, they could not be drained by gravity. The water for them emanated from an artesian well and from the excess water of a pond outside the farm area which overflowed only during the monsoon period.
The expert redesigned the water supply system where possible to enable easier filling of the ponds. He also designed four new ponds which could be drained by gravity flow. Four other breeding ponds adjoining the farm-house and artesian well could be expanded and improve the pond area. Further consideration should be given to this suggestion.
Spawning of common carp failed during the 1964 monsoon period - apparently due to lack of suitable brood stock. In subsequent years the spawning results in this station were satisfactory. Spawning of carp in Janakpur should be done at a time when the water is less than 30°C.
The water supply on this farm, similar to that of all the surrounding agricultural farms, was just under development. Before 1965, the water had to be pumped in, or rain water used to fill the ponds, but after that date, a proper supply system was developed.
Below the farm there is a depression suitable for a large pond and plans for its construction have already been made. In February 1965, the whole area was surveyed by the expert and means found to drain the existing ponds naturally. Precautions were taken during the construction of the outlets to prevent clogging of the pipe system.
Funds for the construction of a 15 000-m2 spring pond became available in February 1965 and so profiles were erected around it and an outlet sluice-type structure designed. Approximately 2 600 m3 (94 000 ft3) of earth had to be moved to convert this swampy depression into a production pond. It was finished in 1966.
Adjoining the housing area to the east in this station site the expert found that by building barriers in another “Gol”-spring-fed swampy depression, not only could the existing pond area be filled with water by gravity, but a second pond of about 15 000 m2 could also be built by moving approximately 2 800 m3 (100 000 ft3) of earth.
A survey of this project indicated that the farm should be closed. The ponds of excavated type were filled by pumping water from Phewatal. The area was rather small and on a lake with an established fish population. There appears to be no special justification for the farm except probably as temporary storage for live fish landed from the lake prior to marketing.
The heavy monsoon rains cause these ponds to overflow, resulting in the escape of the stocked fish back into the lake. Observations should be made on the catches of fish from this lake for the next few years to determine the effect of carp on the native species.
