The Government of Nepal, assisted by the United Nations Development Programme and the Food and Agriculture Organization of the United Nations, is engaged in the Integrated Fisheries and Fish Culture Development Project (NEP/73/025). The project aims to exploit the potential for fish production in the Pokhara Development Region through fish culture in ponds, cages and pens within lakes, stocking of lakes with suitable species of fish, and through fish culture integrated with animal husbandry, e.g. ducks and pigs. A number of related activities are also included such as a limnological/biological study of the lakes, introduction of improved boats and fishing methods as well as provision of improved marketing facilities.
Owing to poor soil conditions the potential for fish production in Pokhara through culture in ponds is very limited. According to an estimate by the Fishery Development Centre, the potential is only around 10 hectares, consisting of scattered ponds of about 800–900 square metres each.
However, the Pokhara Valley has three important lakes, Phewa Lake (400 ha), Begnas Lake (225 ha) and Rupa Lake (120 ha). There are also a few smaller lakes, such as Khaste (15 ha) and Deepang and Maidi (less than 10 ha each).
The total natural production of fish from the lakes and rivers in the Pokhara Valley has been estimated to be around 23–25 tons per year. The catch consists of indigeneous species of which mahaseer (Tor tor), catle (Barbus hexagonolepis), asla (Schizothorax spp.) and baam (Mastacembelus spp.) are most sought after by the consumer. The bulk of the catch, however, consists of smaller species of fish which are consumed when the better quality fish are unobtainable. In recent years some stocking has been carried out in the lakes of the Pokhara Valley with common carp and Chinese carps, as well as the Indian major carp rohu (Labeo rohita). These have recently begun appearing in small numbers in the fish catches and have been readily accepted by the consumer.
On the basis of statistical studies (Ferro, 1979a), the catches from the three major lakes for the period March 1977 - February 1978 have been estimated to be 7.5 t for Phewa, 5.5 t for Begnas and 3 t for Rupa. Ferro (1979b) estimates that the natural production could be raised to about 20 t in Phewa, and about 15 t each for Begnas and Rupa, through appropriate stocking and adoption of conservation measures. Ferro (1979b) also mentioned that cage fish culture could be more effective in harvesting the lakes than natural fishing. Plankton is available in the lakes and could be utilized by plankton feeding fish while others, such as the grass carp and common carp, would depend on feed introduced into the cages.
The advantages of cage culture of fish are as follows: since there is constant circulation of water through the meshes of the cages, there is relatively less accumulation of metabolic wastes, and constant renewal of oxygenated water within the cage. This enables higher stocking rates and consequently, higher production per unit volume than in ponds. The raising of fish in cages also reduces the risk of predation by carnivorous fish and other animals. The main constraint would be feed, which has to be introduced in the case of species depending on non-planktonic food. In contrast to natural fishing, where fishermen have to depend on chance, raising fish in cages enables a predictable and more assured source of income. Better management and control of stocks is also possible.
Preliminary experiments on cage fish culture were carried out by the Government of Nepal from the early 1970's with the assistance of the Japanese Overseas Co-operation Volunteers. Floating nylon net cages imported from Japan were tried out using common carp and silver carp in Phewa Lake and silver carp alone in Begnas Lake.
Since 1976/77 the Integrated Fishery Development Project (NEP/73/025) has carried out more experiments using various locally available materials and combinations of local materials and imported materials for cage construction. In addition to the two earlier species, grass carp and rohu were tried, and experiments with bighead carp were commenced from late 1978. From these experiments it was included that the cage fish culture could be carried out on an economic basis and a programme for increasing fish production by this means in the private sector was launched.