by
H.S. Raina
NRC on Coldwater Fisheries (ICAR), Haldwani-263 139, Distt. Nainital (U.P.), India
and
T. Petr
27 McLeod Street, Toowoomba Qld 4350, Australia
Lakes in Kashmir Valley (state of Jammu and Kashmir), situated at an altitude of 1537 to 1587 m, and Gobindsagar and Pong reservoirs (altitude 560 and 436 m, respectively) at the foot of the Himalayas in the state of Himachal Pradesh, are the major coldwater fishing water bodies in the Himalayas. In both types of water bodies there is a commercial and a subsistence fishery, based on exotic and indigenous fish species. The large floodplain lakes Wular and Dal in Kashmir Valley have an average annual fish yield of 16.5 kg ha-1 and 21 kg ha-1 respectively. Gobindsagar Reservoir, with 60.2 kg ha-1 in 1996-97, has the highest yield of all Indian reservoirs. Its catches are highly dominated by the exotic silver carp, but the indigenous mahseer (Tor putitora) is still a common fish. The Kumaon lakes (altitude 1220-1937 m) in the state of Uttar Pradesh are small in size, with their yields ranging from 0.7 to 9.3 kg ha-1, and the major fish species being the introduced Indian major carps, common carp, and indigenous mahseers. Only some glacial lakes (altitude 3200-3819 m) of Kashmir contain fish, such as brown trout and the endemic schizothoracine Diptychus maculatus. Licence fishing for trout is allowed. The floodplain lakes in Kashmir Valley are rapidly ageing, with their water area being reduced by encroachment of agriculture on lake margins and by a massive aquatic plant growth, which is enhanced by pollution from the surrounding land.
The Himalayas are the main watersheds in the Indo-Gangetic region, having numerous rivers, streams, lakes and reservoirs. The total number of lakes and their area is not fully known. Until recently, most of our knowledge on fish and fisheries in Himalayan lakes was limited to those located in the lower altitudes.
The retreat of glaciers resulted in the creation of many lakes in Kashmir, Uttar Pradesh and Sikkim, while landslides and tectonic movements caused the formation of other lakes. Lakes are present at high altitude in the Great Himalaya and Trans-Himalaya, with the highest lake situated at 5297 m a.s.l. Jana (1998) lists 13 lakes situated from 3400 m to
5297 m, some of them being brackish or saline. Freshwater lakes in Kashmir Valley are believed to have originated as oxbow lakes of the Jhelum River.
Large lakes, the largest 15,300 ha in surface area, are located at middle altitude (1537 to 1587 m) in the State of Jammu and Kashmir. Kumaon lakes in Uttar Pradesh (1237 to 1930 m), all located within a radius of 25 km of the town Nainital, are much smaller, with the largest only 72 ha. All mid-altitude lakes contain fish. In Himachal Pradesh coldwater lakes are situated between 1306 and 4815 m. A list of the major Himalayan lakes of India, giving their altitudes and overall water quality, is presented as Table 1.
The largest floodplain lakes in the Kashmir Valley are Wular, Dal and Manasbal (Fig. 1), all situated at 34oN latitude. Rains are frequent during winter and spring, in late December-February. The precipitation in winter is mainly in the form of snow. These lakes are shallow, with the mean depth for all three ranging from 0.6 to 3.0 m, and the maximum from 5.8 to 13 m (Table 2). Because of its shallowness Lake Wular does not thermally stratify, unlike Lake Manasbal which experiences an oxygen deficit in the bottom layer of water (Wanganeo, 1984).
Kashmir Valley lakes have water with alkaline character (pH 7.4-9.6), the high pH values in summer being the result of an intensive photosynthetic activity from rich phytoplankton. The vertical gradient of dissolved oxygen concentrations differs from lake to lake. In Lake Wular, which is mixed throughout the year, oxygen concentrations do not vary much from the surface to the bottom. Lake Manasbal and the Nagin basin of Lake Dal have a clinograde type of oxygen profile, i.e. with the depth the dissolved oxygen concentration decreases. The lower water layers of the two lakes get oxygen depletion during the summer period which indicates that the lakes are eutrophic. This is further confirmed by high concentrations of phosphorus in summer. Zutshi (1989) noted a net positive input of 4.36 t of phosphorus and 39.2 t of nitrogen per annum in Lake Dal. This is the result of a high input of nutrients reaching the lake from human settlements, hotels and arable land surrounding it.
Further evidence of high inputs of nutrients in these lakes comes from the extensive cover of aquatic macrophytes. Macrophytes occupy nearly 80% of Lake Dal, with the dominance of Myriophyllum, Ceratophyllum, Potamogeton, Hydrilla, Nymphoides and Salvinia (Kant and Kachroo, 1977). About 8 t of carbon per ha is fixed annually by macrophytes giving a ratio of 1:8 between phytoplankton and macrophytic carbon in this system, which suggests that in floodplain lakes of Kashmir Valley the dominant producer may not be phytoplankton, but aquatic macrophytes. Zooplankton concentrations are rather low, although there is no direct zooplankton consumer in the lakes (Wanganeo, 1984). The highest density of benthos was recorded in Lake Wular, followed by Lake Manasbal and Lake Dal.
Most fish species inhabiting the Himalayan region are small in size. Their distribution depends on environmental conditions such as current velocity, nature of substratum, and the availability of food. Schizothoracines, the indigenous cyprinids (also called snow trout), are well adapted to such conditions. They are fish of streams and lakes, and are fished by subsistence, full and part-time fishermen. Ecological degradation of water bodies and overfishing have led to a decline in schizothoracine fish stocks.
In floodplain lakes of Kashmir Valley the major species are: Schizothorax niger, S. micropogon, S. curvirostris, S. planifrons, Schizothoraichthys esocinus, Labeo dero, L. dyocheilus, Crossocheilus latius, Puntius conchonicus, Glyptothorax kashmiriensis, and Gambusia affinis. Schizothoracines are highly valued fish, preferred to most other fish species. They feed on detritus, attached plant (including algal) coating of stones and rocks, and the associated invertebrate fauna. They grow slowly, and attain maturity at the age of 2 years (Sunder and Subla, 1984). All species of the group except S. niger exhibit spawning migration to the incoming streams and rivers and lay eggs in shallow pools amidst gravel and sand. S. niger, however, prefers clean and cold pockets of water in lakes for egg-laying, and it also lays eggs on the roots of willow trees (Vass and Raina, 1979). The spawning season extends from spring to early summer. The average fecundity of this group ranges between 10,000 and 40,000 eggs per kg body weight, the lowest being in S. niger, and the highest in S. esocinus. During the breeding season schizothoracines exhibit sexual dimorphism (Raina, 1976). Details on the biology of schizothoracines are given in Table 3.
In 1959 common carp was introduced in Kashmir to augment the fish yield (Sehgal, 1989). Since then, this species has invaded all the meandering rivers, floodplain lakes and wetlands, and it has become a major commercial fish in Kashmir Valley. More recently its stocks and the mean size of fish have been declining owing to the heavy fishing pressure (Raina, 1987). While the catch rate in 1977 was 850 grams per man hour, in 1984 it was only 325 g/m/h.
In the Kashmir lakes common carp spawns from May to June in beds of aquatic plants, such as Ceratophyllum, Myriophyllum, Potamogeton, and Hydrilla. Eutrophication has contributed to the rapid increase in Salvinia natans (Jana, 1998). In the late 1980s mechanical harvesters were employed against the aquatic macrophytes, but such harvesters do not remove floating plants such as Salvinia.
Most fishing is done by cast nets. Other fishing methods use long-lines, scoop nets and traps, which account for 5-7% of the total fishing gear. Fish production from floodplain lakes is not well documented. Available data show that prior to the introduction of common carp the fish yield was low. With its introduction in Kashmir, yields have increased spectacularly. During 1974-77 Pandit and Qadri (1986) recorded a mean annual catch of
1640 t. Common carp constituted 1380 t, while schizothoracines represented 387 t of the total catch. The average fish yield in Lake Dal was estimated to be 16.5 kg ha-1, and that in Lake Wular 17-25 kg ha-1 (Vass and Zutshi, 1983).
In Kashmir, wetlands called sars cover more than 4000 ha and serve as a natural refuge for a wide variety of organisms. The wetlands are situated on floodplains of the River Jhelum. While some wetlands, such as Haigam and Hokarsar, are maintained by the State Government as bird sanctuaries, as they provide excellent habitats for water fowl, wild duck and geese migrating from China, Russia and other distant regions during winter, wetlands are also important habitats for fish. The principal species using wetlands are common carp, Schizothorax niger, Crossocheilus latus, Puntius conchonius and Gambusia affinis. The fish yield in wetlands varies from 15 to 30 kg ha-1 yr-1. In wetlands minnows are caught with scoop nets in large numbers during summer months. The fish is sun-dried or smoked and it fetches a high price.
Twelve high-altitude lakes are located in Kashmir at a distance of 60 to 130 km from Srinagar. They were visited in summer months during the period 1977-1984 to obtain information on the status of their limnology and fish stocks (Vass et al., 1989). The location of these lakes is shown in Fig. 2, and basic data on their morphology and limnology are in
Table 4. The 12 lakes are located from 3200 m to 3819 m in altitude, and they range from 1 ha to 157 ha in size. Some lakes reach a maximum depth of 80 m.
The high mountain lakes have rocky watersheds, with little or no plant cover. Summer rains are scarce and the water in the lakes comes mainly from snow-melt from glaciers on the surrounding mountains. The lakes are covered with ice for six to nine months. Water transparency in the glacial lakes is determined by the concentration of suspended sediments, which are mainly glacial silt, and by plankton in summer months. Water transparency ranges from 0.5 to 12 m Secchi disc. Summer surface water temperature reaches 15oC, but the average summer water temperature does not exceed 13oC. Most lakes develop summer stratification, with a temperature difference of 8-9oC between epilimnion and hypolimnion. High values of dissolved oxygen, pH of 6.7-7.4, low concentrations of nitrogen and phosphorus, and conductivity of 15 to 130 µmhos are some other abiotic characteristics which suggest that most of these lakes are oligotrophic. Phytoplankton is dominated by diatoms, followed by green algae. Lakes Konsernag and Kishansar are rich in blue-green algae (Vass et al., 1989). Zooplankton is dominated by copepods.
Of the twelve lakes, six contain fish. Four lakes (Gangabal, Nundkol, Kishansar and Vishansar) contain the exotic brown trout (Vass et al., 1989). Lakes Gadsar and Zumsar have an endemic schizothoracine Diptychus maculatus. This fish is also present in the inflowing streams. Like other schizothoracines, it feeds on benthic plants, mainly on those attached to rocks and stones, and on the associated benthic invertebrates. Diptychus, which is a common fish in the two lakes, reaches 225 mm and 125 g in weight at the age of 7 years. It has a low fecundity of up to 380 eggs (in a 125g female). It is fished for subsistence by herdsmen during summer. Brown trout is allowed to be fished with fly, but only by licenced anglers.
Lake Chandertal (4270 m altitude), located in Lahul Spiti district of Himachal Pradesh, has been stocked with brown trout by the Himachal Pradesh Fisheries Department.
Lakes Nainital, Bhimtal, Naukuchiatal, Khurpatal and Sattal (Tables 5 and 6) are situated at an altitude from 1220 to 1937 m, and all are at latitude 29oN, within a short distance of each other, and within a 25 km radius of the town Nainital (Fig. 3). All lakes are small, with the largest one, Bhimtal, covering 72 ha. Lake Naukuchiatal is the deepest, with a maximum of 40.8 m.
The water of Kumaon lakes is mostly slightly alkaline. The water stratifies in spring and mixes during winter. Lake Nainital is eutrophic, with a concentration of carbonates of 288 mg l-1, nitrogen 512 _g l-1, and phosphorus 22.5 _g l-1 (Sharma and Pant, 1985). Bhimtal and Naukuchiatal have moderate levels of nutrients and are mesotrophic. Lakes Khurpatal and Sattal are poor in nutrients. The rising level of nitrogen in Lake Nainital indicates an increasing pollution: in 1955 the ammonium nitrogen and nitrite nitrogen were 23 _g l-1 and traces, respectively, in 1975 the corresponding values were 156 _g l-1 and 18 _g l-1 (Pant et al., 1985). The result has been an increase in biological production, leading to a higher organic matter production and its deposition on the bottom, resulting in anoxic conditions in the bottom water layers. Winter mortality of fish in Lake Nainital and Lake Naukuchiatal is now a regular feature.
Large areas of lakes Sattal, Bhimtal, Nainital and Naukuchiatal are now infested with aquatic macrophytes, such as Polygonum, Hydrilla, Potamogeton, Myriophyllum and Vallisneria. In addition, Nainital also accumulates detritus from human activities around the lake. In Nainital, water is considered to be of poorer quality than in the other lakes, and this lake also experiences fish kill during winter.
Johri et al. (1989) presented fish catch data for the period 1983-1988 for Bhimtal, Naukuchiatal and Sattal, which are managed by the Department of Fisheries. No data are available for Nainital, which is controlled by Nagar Palika (Nainital), an organisation responsible also for the monitoring of the inputs of pollutants in this lake. Mahseers (Tor tor and T. putitora) dominated the catches in Bhimtal and Naukuchiatal, with 59.5 and 45.0% respectively of the total for the five-year period. Common carp followed, with 34.8 and 31.5% respectively, while in Sattal it formed 22.9% of the total catch. Indian major carps (Labeo rohita, Cirrhinus mrigala and Catla catla), dominated the catches in Sattal with 64.1% of the total. Schizothoracines (e.g. Schizothorax richardsonii) represented 0.73 and 0.95% in lakes Bhimtal and Naukuchiatal, but were absent in Sattal. Silver and grass carps, introduced in Bhimtal in 1985-86, appeared in catches from that year onwards. The average yields (kg ha-1 yr-1) for the five-year period were as follows: Bhimtal (area 86.5 ha): 9.32; Naukuchiatal (65 ha): 0.74; Sattal (24.5 ha): 13.4. Bhimtal provides good conditions for catla and rohu, and Naukuchiatal for mrigal. The low yield for Lake Naukuchiatal seems to result from the lower fishing intensity. As a remedy it has been proposed to regularly stock this lake with fingerlings of mahseer, common carp, Indian major carps, silver carp and grass carp. Stocking the Kumaon lakes is considered essential for increasing fish yields, which, it is estimated, could be increased to 25-50 kg ha-1 yr-1(Johri et al., 1989).
From the fishery point of view, Gobindsagar (elevation 560 m) and Pong (elevation 436 m) are the two most important reservoirs of the Himalayan foothills in Himachal Pradesh. These reservoirs are the leading sources of fish supply among the Himalayan States. Fish landings from Gobindsagar account for 58 to 60% of the total fish production in Himachal Pradesh. Due to directly receiving cool water from the Himalayas, both reservoirs, in spite of being situated at a relatively low altitude, contain stocks of coldwater fish.
5.1 Gobindsagar Reservoir (Fig. 4)
This reservoir was created in 1963 as a result of the impoundment of the Sutlej River at Bhakra. The Sutlej receives cool, snow-melt water during the spring and summer months and water from monsoon precipitation in its lower catchment during July-September. Downstream of the reservoir, the Sutlej joins the Beas River and enters Pakistan. In 1978 the Beas-Sutlej Link (BSL) was completed, diverting Beas water to Gobindsagar in order to augment the power generation and irrigation capacity of the reservoir (Sugunan, 1995). Blending of the cool Beas water and the warmer Sutlej water in the reservoir has led to a unique pattern in the thermal and oxygen regime and in dissolved chemical components, and this in turn has had an impact on the life and production cycle of aquatic organisms. For morphometric features of the reservoir see Table 7, and for physico-chemical parameters Table 8.
At full storage level, the reservoir has a surface area of 15,867 ha, while at the minimum dead storage the level is 5063 ha. The annual water fluctuation varies from 41 to 61 m, and the maximum amplitude is 70 m. The reservoir is 168 km long, and 6 km wide near the dam. Before the completion of BSL the water temperature ranged from 17 to 27oC. After the BSL was connected, in the area influenced by Beas water the temperature never exceeded 18oC, with a concomitant rise in dissolved oxygen level. The incoming cold water remains as a distinct layer at the bottom (Sugunan, 1995).
Prior to the construction of the dam, the upper reaches of the Sutlej River used to have 30 species of fish, of which Tor putitora, Labeo dero, L. dyocheilus, Schizothorax and Aorichthys seenghala were the dominant species. In 1961-62 Gobindsagar was stocked with the Indian major carps Catla catla, Labeo rohita and Cirrhinus mrigala, and this was followed by a regular stocking of common carp. Jhingran and Sehgal (1978) and Rao and Natrajan (1979) reported 51 species, subspecies and varieties of fish present in Gobindsagar. The emergence of silver carp in the reservoir in 1979 marked the beginning of a radical change in the catch structure, with this fish establishing an overriding dominance over all other species, percentage-wise (Sugunan, 1995).
Today, the introduced silver carp and common carp dominate the total catch. The other commercially important fish are: Catla catla, Tor putitora, Labeo rohita, Cirrhinus mrigala, Labeo calbasu, Aorichthys seenghala and Schizothorax plagiostomus. Indian major carps were increasing from 1974 to 1988. A sharp decline in Labeo rohita was observed from 1979 on. While its percentage proportion in catches increased from 7.7% in 1974 to 23.5% in 1978, by 1988 it had declined to 0.5% of the total catch. Catla catla declined from 31% in 1977 to 5.3% in 1988, and Cirrhinus mrigala from 16.8% to 0.3% over the same period. Minor carps are represented mainly by Labeo dero, L. dyocheilus, Cirrhinus reba and Puntius sarana. Their proportion in catches increased until 1982, followed by decline. Their percentage proportion in catch reached the all time low in 1989-90, but then recovered to some extent (Sugunan, 1995).
After their introduction, common carp and silver carp gradually increased their proportion in the total catch, with common carp peaking in 1982-83 (Kumar, 1988). After that common carp declined to the level of the total for the Indian major carps, while silver carp continued to increase its absolute and percentage proportion in the total catch (Table 9). Gobindsagar is the only Indian reservoir where silver carp has produced a self-sustaining stock. The major disadvantages of the fish is its poor shelf life and low market preference. The low sales price of the fish is compensated for to some extent by the quantity captured: in 1992-93 it represented 71.6% of the total catch by weight. The total annual catches from Gobindsagar have continued to increase, with 1016 t achieved in 1996-97, much of it being silver carp (Kumar, 1997).
From 1974 onwards there has been a moderate increase in the quantity of captured mahseer but its percentage declined with the increasing total annual fish catch. While during 1974-75, 28.7 t of mahseer were captured (16.8% of the total catch), in 1992-93, 46 t captured represented only 0.5% of the total. The rapid increase in silver carp has not had any impact on mahseer stocks.
Fisheries management of Gobindsagar Reservoir has included a programme of stocking and harvesting. The inadvertent introduction of silver carp has helped to build up the stocks of food fish in this reservoir. From 1976 onwards the Fisheries Department assisted in organising about 1000 fishermen families into cooperatives. Further management measures have been the enforcement of mesh size regulation and imposition of a closed season during the breeding of some commercially important fish species. The capture and marketing of fish is managed by the fishery cooperative societies. Several welfare schemes, such as provision of subsidies for purchase of fishing equipment and a personal accident insurance scheme introduced by the Government, have helped the communities to raise their status.
5.2 Pong and Pandoh reservoirs
Pong Reservoir (Fig.4) on the Beas River in Himachal Pradesh covers an area of 24,529 ha. The Beas and its tributaries are snow-melt or glacier fed. The reservoir is 42 km long, and 19 km wide in its widest part; its mean depth is 35.7 m. While the surface water temperature varies between 22.2 and 25.1oC, the incoming river water has a temperature range of 6 to 26oC (Sugunan, 1995). Other physico-chemical characteristics of the reservoir
water are as follows: Secchi disc transparency 0.12-4.8 m; pH 7.0-8.4; silicates 3.0-5.0 mg l-1; chlorides 6.0-7.0 mg l-1, total hardness 22-28 mg l-1 (Sehgal, 1989a). Sugunan (1995) gives total hardness range from 19 to 68 mg l-1, and he also provides the following information: total alkalinity 53-81 mg l-1; specific conductivity 173-190 µmhos.
Pong is a shallow reservoir with a lower organic production than Gobindsagar and the fish fauna was originally dominated by catfishes, minor carps and a few coarse fish. On account of systematic stocking of common carp and Indian major carps, with the first introductions of common carp in 1974 and Indian major carps in 1976-77, the catch structure of the reservoir was completely altered and carps eventually accounted for 61.8% of the total landings (1987-88). Today, the important fish species in order of abundance are: Labeo rohita, Aorichthys seenghala, Labeo calbasu, Tor putitora, Cirrhinus mrigala, Wallago attu, Cyprinus carpio, Labeo dero, Catla catla, and Channa spp (Sugunan, 1995). Mahseer stocks declined from 101.5 t in 1982-83 to 54 t in 1989-90 (Table 10). In 1989-90 the fish yield was 20.4 kg ha-1, and the maximum of 33.2 kg ha-1 was recorded in 1987-88. The yields are calculated for the full reservoir surface area.
The construction of the Gobindsagar and Pong reservoirs has created a perennial source of fish supply for the people of Himachal Pradesh and adjoining states, but certain valuable migratory species have been adversely affected. The golden mahseer (Tor putitora) is no longer able to migrate into Kangra Valley due to the presence of the dam at Pong. Luckily, the mahseer has established self-reproducing stocks within the new limits. The impact of damming on schizothoracines has been more serious.
Pandoh Reservoir (altitude 987 m, 200 ha) forms part of the Beas-Sutlej Link Project, diverting the Beas water into the Sutlej basin. Water temperature is 16.5-10.5oC, specific conductivity 91 µmhos. Common carp was stocked in 1978, but stocking has been discontinued. The reservoir is used for occasional recreational/sport fishing. Brown trout, snow trout Schizothorax richardsonii, Labeo dero, L. dyocheilus, Tor putitora and some other hill-stream fish are present in its waters (Sugunan, 1995).
The gradual, but continuous increase in fish catches from the reservoirs Gobindsagar and Pong, has led to a stable commercial fishery, which provides full employment to over 4000 fishermen, traders, retailers and some other professions (Kumar, 1997). During 1996-97, over 1400 t of fish were landed from both reservoirs, of which about 400 t came from Pong. While Gobindsagar is known for its record landings, Pong has the reputation for an excellent quality of fish. Pong fish get the highest per unit price. Pong is also a favourite place for anglers, who fish out about 60-70 t of golden mahseer annually. Both reservoirs are judiciously managed at State level by the Reservoirs Fisheries Development Committee, which is now focusing on the improvement of the fisherfolk living conditions and on social safety, such as accident insurance, risk fund, and savings-cum-relief scheme, the last providing financial assistance to fishermen during the fishing ban period. The Scheme has also assisted in securing the fishermen's cooperation in supervising the ban on fishing (Kumar, 1997).
It is believed that the ecological degradation of the Himalayan lakes has not yet reached the state of no return. Dal and Wular lakes in Kashmir, and Nainital in Uttar Pradesh, have especially been adversely affected by pollution and poor management of land in their catchments. The lakes are undergoing eutrophication and biological degradation. The following discusses some ways of improving the current situation.
In recent years the increase in land use as a result of intensive agriculture and urbanisation in watersheds has resulted in an increased input of organic waste into rivers and lakes. This has led to eutrophication of some lakes, and pollution of streams. Lakes Nainital and Bhimtal in Kumaon, and lakes Wular and Dal in Kashmir are examples of such an impact. Lake Dal is facing a serious problem of shrinkage. Between 1911 and 1984 the open water area was reduced from 1507 ha to 700 ha, while marshy areas increased form 800 to 1530 ha. 40,000 to 52,000 t of dead aquatic plants and other organic material from intensive agricultural and horticultural activities on the margins of the lake are added annually. Lake Dal is also suffering from the input of domestic waste from anchored boats, lakeside hotels and settlements along its shore. This alarming situation calls for urgent remedial measures if Lake Dal is not to disappear in the not so distant future.
Lake Manasbal is also undergoing eutrophication due to the increased input of nutrients from various human sources.
The entire catchment of Kashmir Valley ultimately drains into Lake Wular before the outflowing waters leave India for Pakistan as the Jhelum River. Lake Wular has been reduced in size from 27,500 ha to 15,200 ha, and its mean depth is now 1.5 m, instead of 3 m. There has been a rapid encroachment of agriculture, especially rice paddies, on the margins of the lake. Construction of embankments to protect crops against flooding, and planting trees along the margins under a social forestry programme have also contributed to the process of shrinking of the lake. The open lake water area has been further diminished by the introduction of floating islands for vegetable cultivation. The shallowness of the lake has become a hindrance for navigation, including recreational boating. The changes have also adversely affected fish production and the growth of lotus and Trapa plants, and the number of game birds has been declining.
In the Kumaon, the growing demands of local residents to meet the challenge of increasing tourism and other development programmes have increased pressure on Lake Nainital. Kumaon Himalaya, especially the lakes, have been witnessing a dramatic increase in recreation. In Nainital, the numbers of tourists increased from 160,000 in 1958 to 680,000 in 1986 (Singh, 1989). Lake Nainital has been so badly damaged by the input of sewage that it cannot fully recover even if the pollution discharge into the lake is diverted (Sharma and Pant, 1985). Fish kill in some Kumaon lakes has now become an annual occurrence.
In 1988, in the State Jammu and Kashmir there were 9976 full-time fishermen. In Kumaon Himalaya there are no such professional fishermen, but angling is common in Bhimtal, Naukuchiatal and Sattal. Fishermen fishing Gobindsagar and Pong reservoirs in Himachal Pradesh are organised in cooperative societies.
The impact of the introduction of exotic species on endemic coldwater fish in the Himalayan uplands is quite significant. The introduction of common carp may have adversely affected the endemic schizothoracines and mahseers. In Lake Dal in Kashmir, Kumaon lakes in Uttar Pradesh, and the reservoirs Gobindsagar and Pong in Himachal Pradesh the introduced common carp and silver carp have become the dominant fish. How far the presence of these carps has contributed to the decline in the endemic species is difficult to say. While the decline in schizothoracines is obvious, a modest increase in mahseer has been recorded in Gobindsagar reservoir. Damming of rivers and eutrophication of lakes have probably been the major negative impacts on schizothoracines, rather then the presence of common carp and silver carp. Silver carp is limited in its distribution to only one Himalayan water body, i.e. Gobindsagar Reservoir, where it reproduces.
Apart from the well-organised fishery in the two reservoirs, and the fishery in the two large Kashmir lakes Wular and Dal, the Himalayan lakes will probably remain largely at a subsistence and sport/recreational fishery level. More attention needs to be paid to prevent indiscriminate fishing, and to the enforcement of closed seasons and mesh size limits. Environmental aspects, especially rehabilitation of watersheds to prevent excessive siltation of rivers and lakes, and prevention of pollution to reduce the rapid eutrophication of some lakes and reservoirs, also need to be urgently addressed.
Enhancement of lake and reservoir fish stocks will require continuous hatchery production of a sufficient number of stocking material, especially common carp and the indigenous mahseers and schizothoracines. In some lakes, where it would not lead to an increase in the rate of eutrophication, a pilot scale cage culture could be tested and introduced.
High mountain glacial lakes, with their oligotrophic character and low water temperatures, appear to have little chance for becoming productive fishery water bodies. Where deemed realistic, stocks of brown trout and/or schizothoracines could be maintained through stocking. Lakes holding already self-sustaining stocks of brown trout and schizothoracines should be carefully managed to avoid overfishing. Some of these water bodies should be selected as fish sanctuaries.
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