1. OBSERVATIONS, RESULTS AND CONCLUSIONS

Feeding experiments

These were carried out in the 4 ponds available at Kajansi Experimental Station, and in 11 ponds on 8 private farms. Experiments were made using common carp (Cyprinus carpio), but mixed culture of carp and Tilapia hybrids (monosex hybrid of T. mossambica and T. nilotica) was tried in two farmers' ponds. Feeds tried were corn meal (locally called posho), brewery grains, local beer dregs or wastes, groundnut cake and cottonseed meal. Experiments were carried out for 90 days at the government station and 120 days in the farmers' ponds. Analysis of the composition of the various feed materials is shown in Table 1.

Table 1

COMPOSITION OF FEEDS USED IN EXPERIMENTS¹

¹ This analysis was made by the Veterinary Institute, Entebbe.

At the Kajansi station two experiments were conducted. The first was carried out in four 0.5 acre (0.2 ha) ponds as follows:

The experiment lasted 93 days in B-1 and B-5, and 94 days in B-4 and B-6. Table 2 gives the results.

Table 2

RESULTS OF FIRST FEEDING EXPERIMENTS IN KAJANSI STATION

¹ Average weight of original fish stocked - 2.8 g.
² Based on 300-day rearing period per year

The second experiment in the same ponds was undertaken to confirm the value of using beer dregs as fish feed. In this case, feeding was done at two stocking rates, namely, 600/acre (1 500/ha) and 1 000/acre (2 500/ha), using one pond in each case fed with beer dregs (B-4 and B-6) and the other as control without feed (B-1 and B-5). The results are shown in Table 3.

Table 3

RESULTS OF THE SECOND FEEDING EXPERIMENT IN KAJANSI STATION

¹ Fish stocked in B-1 and B-4 averaged 112 g, while those in B-5 and B-6 averaged 2 g.
² Based on 300-day rearing period per year.

Further feeding experiments were conducted in 11 farmers' ponds in the Mengo district, near Kajansi. In this, corn meal alone, 50:50 mixture of corn meal and beer dregs, and beer dregs alone, were used in the different experimental ponds. Table 4 outlines the results.

Owing to inadequate supplies of stocking material, it was not possible to carry out the experiments on a larger scale or for a longer period. However, the results of one 90-to 120-day culture in different ponds gave an indication as to what could be expected from longer rearing periods and possibly also from larger ponds.

Table 4

RESULTS OF FEEDING EXPERIMENTS IN FARMERS' PONDS

¹ Based on approximately 300-day rearing period/year.
²T - Tilapia, otherwise common carp were used.

In the experiment at the Kajansi station corn meal appeared the best among the feeds used. However, beer dregs also gave fairly good results, followed by a combination of the feeds available. Realizing the importance of cost analysis in the selection of feeds, the costs to produce one kilogram of fish using different feeds were calculated on the basis of the experimental results, and were as follows:

¹ In 1968, 7.14 Uganda shillings = US$1.00

It is clear from the above that beer dregs are the cheapest and most profitable form of feed to use.

“Coffee remains”, or waste coffee husks, the chemical composition of which is shown below, are abundantly available in Uganda and are worthy of being tried as a fish feed. Owing to lack of time the expert was unable to carry out any experiments with this material.

Although the results of the feeding experiments can only be considered as preliminary, there is enough evidence to show that beer dregs could be used with advantage as fish feed.

Experiments on fish pond fertilization

These experiments were conducted in six one-eighth acre (0.05 ha) ponds at the Kajansi Experimental Station. They were designed to continue the studies started by Mr. Y. Pruginin during his assignment in Uganda from 1962 to 1966. The fertilizers tried were chicken manure, superphosphate and ammonium sulphate, either alone or in combination.

Table 5

RESULTS OF POND FERTILIZATION EXPERIMENTS

¹ Based on an average weight of 2 g.
² For a three-month rearing period.
³ The superphosphate used in this experiment had 20 to 21 percent P₂O₅.
⁴ The ammonium sulphate used in this experiment had 26 percent nitrogen.

As can be seen from Table 5, the results of these experiments were not conclusive.

Chemical analyses of the bottom soils of the ponds were made (see Table 6)

The pH of the pond soils used is acidic and the poor production may at least be partly ascribed to this. It may be advisable to lime the ponds before fertilization in subsequent experiments.

Economic aspects of fish culture

The total production of fish from all waters in Uganda in 1966 was estimated to be 80 000 tons, of which 90 percent came from lakes, mainly Lake Victoria. A limited amount, estimated at 112 tons, came from 7 000 units of fish ponds that cover 720 acres (290 ha) located in various regions of the country. As a rule, the pond units are small and shallow, averaging about 0.1 acre (400 m²) and are usually not over 1 m deep. The production is generally low and varies greatly, ranging from 35 to 1 000 kg/ha/yr.

A general survey of the cost of operations of the established fish farms and the income derived or value of produce from such farms was made by the expert in cooperation with native fishery officers. At the present, many fish ponds are not economically run. The underlying factors contributing to this unfavourable situation appear to be:

1. Sites of fish ponds are not properly selected and many are actually built in unsuitable locations.

2. The layout and construction of the ponds are unsatisfactory, with the result that they cannot be managed well after they have been built.

3. The ponds are generally too small for economic operations.

4. General lack of knowledge on the part of fish-pond operators of proper pond management practices, such as fertilization, feeding, pest control and stocking rate and stocking combinations.

Table 6

ANALYSIS OF SOIL SAMPLES FROM PONDS IN THE KAJANSI FISH FARM
(Made by the Kawanda Research Station, Ministry of Agriculture)

These have to be taken into full consideration when formulating future programmes of fish culture development. There is clearly a need for a thorough appraisal and reorientation of programmes to make fish culture an economically viable industry in the country.

Hybridization of Tilapia

Nearly all the ponds in the whole country are small and shallow (less than 0.5 ha), thus, with Tilapia spp. as the main stocking material, early overcrowding of the stock and subsequent stunting results. The hybridization of Tilapia spp. already accomplished enables monosex culture in ponds. The monosex hybrid of T. mossambica from Zanzibar and T. nilotica from Lake Albert has been recommended for culture in Uganda, but the feeding habits of the hybrid are not very suitable and it is more desirable, if possible, to have monosex hybrids of the phytophagous species of Tilapia. The expert, therefore, undertook preliminary experiments in the hybridization of the plant feeding T. zillii and T. melanopleura. Because of lack of adequate facilities, conclusive results could not be obtained; further tests with these two species will be necessary.

Observations on Nile perch

Observations on the condition of gonads of the Nile perch, Lates niloticus, were made at Kabaka “lake”, a water impoundment near Kampala. The expert's preliminary findings showed that Nile perch might spawn in confinement, and that the breeding season extended from at least June to November (the duration of the expert's study) and possibly throughout the year. Examination of the gonads showed eggs in different stages of maturity. The males were more numerous (more than threefold) than females in the populations examined. The egg count for a sexually mature female amounted to 4 500 to 8 000 of the gonad, giving an average of 75 000 to 125 000 eggs/kilogram weight of spawner. The fry of stock reared at the Kajansi station were found to be preyed upon by frogs.

Extension work and training programme

The Fisheries Department under the Ministry of Animal Industry, Game and Fisheries is charged with administering the fishery service for the country. This Department carries out its work of extension, research and training through its various fishery stations. For fish culture promotion, the Kajansi Experimental Station and the various fish culture stations and fry centres serve the general public.

To get the fish culture industry started, full assistance is being rendered by the Fisheries Department. This consists in selection of sites, planning layout, supplying and planting fish stock, feeding and sampling during the rearing period and harvesting. While the above procedure of governmental assistance was highly desirable during the inception of this industry, at present there seems to be a need for re-orientation of government policy in this respect. It appears highly desirable that in as much as several private fish farms have already been established, the task of management and operations should gradually be shifted to private operators in order to determine whether fish culture would be commercially feasible as a private venture.

The production of an adequate number of fish seedlings to provide sufficient stock for the existing fish ponds as well as for future surface expansion would be a big improvement in the fish culture industry in Uganda. The techniques of fish propagation were imparted to counterpart personnel at Kajansi Station and to staff members of other stations, with whom the expert had contact. The fry centres also need to be expanded and provided with proper facilities so that they will be able to undertake the programmes for which they have been built.

Training of counterpart personnel was one of the major duties of the expert. This was done as a routine duty through practical work and demonstrations as well as instruction at the headquarters at Kajansi. But there are still a number of personnel involved in fish culture in the Fisheries Department that cannot be reached by this training. The expert fully endorses the idea of establishing a fishery training centre at Entebbe and he has assisted in formulating training programmes to be implemented in such a centre, once established. Meanwhile, it is hoped that the senior officers already trained by the expert can prepare their immediate assistants for this work. Well-trained extension workers, capable of giving proper advice on fish-pond management, would constitute a major factor in the future of this industry.

Another area where fish culture can contribute to increased fish production is through the stocking and management of dams and reservoirs. At present, there are a number of these reservoirs ranging from a fraction of an acre to as much as 20 or more acres (8 ha +), and more are being built. These impoundments are built usually for storing irrigation water, water for livestock and domestic use. Some of these reservoirs are permanently watered, while some may dry up periodically. Properly stocked with the appropriate number and kinds of fish, and subsequently managed for fish production, these can contribute greatly in increasing production from inland waters.

The production of more seed fish for these waters needs to be accelerated. Installation of facilities to keep the stock from escaping, maintenance and de-weeding of reservoirs, and periodic and systematic cropping of harvestable fish, will be necessary.