Prospects of fisheries enhancement and aquaculture in lakes and reservoirs of Nepal. (by M.K. Shrestha, R.K. Batajoo and G.B. Karki)

Madhav K. Shrestha¹, Rabindra K. Batajoo² and Ganesh B. Karki^3
1Institute of Agriculture and Animal Science, Rampur, Chitwan, Nepal
²District Agriculture Development Office, Pokhara, Kaski, Nepal
³Fisheries Development Center, Kulekhani, Makawanpur, Nepal

ABSTRACT

Aquaculture in open waters is limited to three Pokhara Valley lakes, i.e. Phewa, Begnas and Rupa, and to Kulekhani reservoir. Cage culture in lake Phewa has increased from 66 cages, with 1 800 m³ cage volume, to 340 cages with 15 300 m³ cage volume, during the last 20 years. Pen culture increased from 0.2 ha to 5.5 ha in the last 7 years. In lake Begnas the increase in cage culture was disrupted by a dam, which resulted in an increase of the water surface area, but in a decrease in lake productivity. In lake Rupa, the most productive of the three, a steady increase for 14 years was disrupted by siltation. There is also cage culture in Kulekhani reservoir. Every year fish stocks of lakes and the reservoir are enhanced by stocking fingerlings of planktivorous carps.

1. INTRODUCTION

Nepal is a landlocked country and its natural waters are classified into five categories: (i) rivers and streams, (ii) lakes, (iii) reservoirs, (iv) swamps, and (v) lowland paddy fields. Natural waters are defined as water bodies that are relatively large, without control or little control by humans and balanced by natural ecosystem with indigenous biodiversity. However, swamps and paddy fields are seasonal resources and dry up during the dry period of the year. Rivers and lakes are the non-expandable resources whereas reservoirs are expandable. In Nepal reservoirs are constructed primarily for hydropower generation and irrigation purposes. New reservoirs are under construction, with many reservoirs expected to be completed in the future (Table 1).

Table 1

Water resources of Nepal

Water bodies including rivers, streams, lakes and reservoirs, are used for multiple purposes such as drinking and other household water uses, industrial use, irrigation, aquatic crops production, hydropower generation, recreation and tourism, fisheries, including conservation of aquatic genetic pools, etc. They also provide a habitat for aquaculture production. However, overexploitation of the natural fisheries resources due to high fishing pressure, including damaging fishing methods, has led to decline in natural fish stocks. To improve the fisheries potential, enhancement of wild fish stocks and aquaculture has been initiated in a limited number of lakes and reservoirs of Nepal. This paper describes the status and prospects of fisheries and aquaculture enhancement in lakes and reservoirs of Nepal.

2. LAKES

There are many medium and small lakes in the country, with about 5 000 ha of water surface area (FDD, 1998). These lakes have different origins and can be classified as (a) glacial, (b) tectonic, and (c) oxbow lakes. The high-altitude mountain lakes are glacial, mid-hill lakes are tectonic and most of the Terai lakes are of the oxbow type. Based on the nutrient status of lake water, mountain lakes, mid-hill lake and oxbow lakes are oligotrophic, mesotrophic and eutrophic, respectively (Bhandari, 1998). For the major lakes of Nepal see Table 2.

Table 2

Major lakes of Nepal

3. RESERVOIRS

At present Nepal has only a small number of reservoirs: Jagadishpur, Trishuli, Marshyandi, Kulekhani, Gandaki, Saptakoshi, Andhikhola and Panauti. Their total water surface area is approximately 1 500 ha (Table 3). These reservoirs serve hydropower and irrigation purposes (FDD, 1998).

Table 3

Major reservoirs

4. AQUACULTURE IN LAKES AND RESERVOIRS

Aquaculture is limited to three lakes of the Pokhara valley (Phewa, Begnas and Rupa lake) and one reservoir (Indrasarobar reservoir) of Kulekhani in Nepal. Cage culture as well as pen culture have been practiced in lakes Phewa, Begnas and Rupa since the late 1980s. Technology of cage culture was transferred from the lakes to Indrasarobar reservoir in 1985, but full expansion by private farmers started in 1993 only. Planktivorous carp are now commonly used in extensive cage culture. Cage culture expansion in the four major water bodies of Nepal is presented in Table 4.

Table 4

Cage culture in lakes Phewa, Begnas and Rupa, and in Kulekhani reservoir,
Nepal (public and private sector)

Cage culture in Phewa lake has increased from 66 cages with 1 800 m³ cage volume to 340 cages with 15 300 m³ cage volume during the last 20 years. Pen culture area increased from 0.2 ha to 5.5 ha in the last 7 years. A similar trend of cage culture expansion was observed in Begnas lake from 1980 to 1990, however, this trend was disrupted due to a dam construction in Begnas, which increased the water surface area but decreased the lake productivity. Pen culture in Begnas has been almost constant for the last 7 years. In lake Rupa, one of the most productive lakes, the number of cages grew for 14 years, but this has been followed by a decrease to less than half due to heavy siltation which has resulted in shallowing of the lake. This has led to an increase in pen culture area in lake Rupa (Table 5). Technology of carp cage culture has been successfully transferred to Kulekhani reservoir (Table 4).

Table 5

Pen culture in lakes Phewa, Begnas and Rupa, Nepal (public and private sector)

Fish growth and fish production in extensive cage culture largely depend on the lake trophic status and lake productivity. Fish yields from cage fish culture are presented in Table 6. While the fish production in lakes Phewa and Begnas has been stable, there has been a decrease in lake Rupa. Fish cage culture production in Kulekhani reservoir has been increasing. The total fish production from pen culture in these lakes is about 2.5 t/ha/yr (Pradhan and Shrestha, 1997).

Table 6

Fish production/yields from cage culture in lakes Phewa, Begnas and Rupa and in Indrasarobar reservoir, Nepal

5. FISHERY ENHANCEMENT IN POKHARA VALLEY LAKES AND IN KULEKHANI RESERVOIR

In the past, lakes and reservoirs were used primarily for capture fisheries. Fisheries enhancement through open water stocking of hatchery-bred carps was initiated 23 years ago in three lakes of Pokhara, and 15 years ago in Kulekhani reservoir (Table 7). Since then the fish production in these lakes and the reservoir has increased considerably, except for some accidental fish losses as a result of a substantial water drawdown in Kulekhani reservoir (Table 8).

Table 7

Fingerling stocking in lakes Phewa, Begnas and Rupa, and in Kulekhani reservoir

Table 8

Fish yield (kg/ha/yr) in lakes Phewa, Begnas and Rupa, and in Kulekhani reservoir

6. FUTURE PROSPECTS OF FISHERIES ENHANCEMENT AND AQUACULTURE

Fisheries development in lakes and reservoirs can be achieved through aquaculture (cage culture and pen culture) and fisheries enhancement (open water stocking). Breeding ground protection, selective and seasonal fishing will further improve fish catches. As the lakes and reservoirs are also places attracting tourism and recreation, they must be used judiciously for fisheries development. Lakes can be categorized as (i) protected and conserved lakes, (ii) semi-conserved lakes, (iii) production lakes (Shrestha, 1999).

6.1 Lake fisheries

Protected and conserved lakes: Where natural fish biodiversity can be protected, tourist recreation and boating can be maintained; selective seasonal sport fishing should be allowed. Such lakes are the lakes in national parks and sanctuaries for example lake Rara of Mugu; Bees Hazar Tal of Chitwan; and Badhaiya Tal of Bardia.

Semi-conserved lakes: Where a balance of tourist recreation, boating, sport fishing and fish production needs to be maintained: lakes Phewa and Begnas in Pokhara valley.

Phewa lake: Increasing eutrophication of this lake due to sewage drainage needs to be strictly controlled. Stocks of planktivorous fish species as well as those supporting recreational and sport fishery need to be enhanced. Cage culture of planktivorous fish utilising the natural food (i.e. phytoplankton) should not be expanded beyond 1-2% of water area, and no pen culture should be installed in this lake.

Begnas lake: This lake is oligotrophic in nature. To balance between tourist attraction and recreation and fish production, cage and pen culture should not expand beyond 2-3% of the water surface area. Pen culture should be minimal and not encroach on breeding and nursery grounds of important indigenous species.

Production lakes: All such lakes except those mentioned above can be exploited for fish production both by aquaculture (cage and pen culture) and fisheries enhancements, along with a limited fishery for the indigenous species. Cage culture and pen culture may be expanded to 5% of the total water surface area.

6.2 Reservoir fisheries

Reservoirs are mainly built by damming rivers either for hydroelectricity generation or for irrigation. Damming of rivers disrupts the routes of migratory fish species, affecting their population dynamics, diversity and species composition in the upstream as well as in downstream sections of the rivers. The river fish production may also be affected. Reservoirs are water bodies which offer fish production potential, both for capture fisheries as well for aquaculture. To maintain fish stocks both in the rivers affected by dams, and in reservoirs, the following is considered to be essential:

• fish ladders with sufficient water flow for fish migration should be provided wherever applicable,

• local fish hatchery should be established for stock enhancement in reservoirs and rivers,

• priority for stock enhancement should be given to economically important local species,

• cage and pen culture should be given to economically important species wherever applicable.

7. CONCLUSIONS

Fisheries enhancement of capture fisheries and aquaculture in lakes and reservoirs of Nepal are two important strategies for meeting the increasing demand for aquatic products in the country. However, fisheries resources need to be used judiciously to preserve the fish genetic biodiversity, and to remain an attraction as well as source of food for tourists and nationals. Good environment protection and fishery management of lakes and reservoirs are essential for keeping good fish stocks in these water bodies. Community ownership and participation in the management of water bodies will assist in developing and maintaining sustainable fisheries.

References

Bhandari, B., 1998. An inventory of Nepal's wetlands. Final Report, Kathmandu Nepal: IUCN Nepal, Wetlands and Heritage Unit.

FDD., 1998. Annual Progress Report (1997/98). Fisheries Development Division. Department of Agriculture, HMG, Nepal.

Pradhan, G.B.N. and S.B. Shrestha, 1997. Status of fisheries and aquaculture development and their potential for expansion in Nepal. In: D.B. Swar, G.B.N. Pradhan and L.M. Lofvall Westlund (eds.): Proceeding of National Symposium on Role of Fisheries and Aquaculture in the Economic Development of Rural Nepal, 15-16 August. 1996. Kathmandu, NEFIS, Nepal.

Shrestha, M.K., 1999. Status review, production potentials and strategy for sustainable management of open water fishery of Nepal. Paper presented at: Study Meeting on Sustainable Fishery Management. STM-09-99, 13-21 October 1999, Tokyo, Japan.