by
K.L. Sehgal
NRC on Coldwater Fisheries (ICAR)
Haldwani-263 139, Distt. Nainital (U.P.), India
The Himalayas, which run for about 2500 km from west to east, are drained by 19 major rivers. The eastern Himalaya has a greater diversity of coldwater fish than the western Himalaya. 218 fish species are listed for the whole Himalayas. Subsistence and commercial fisheries exploit the larger fish, such as the cyprinids Labeo dero, Tor putitora, Tor tor, Barilius bendelisis, Schizothorax richardsonii and Schizothoraichthys esocinus, as well as Garra gotyla and Crossocheilus diplochilus. The other fish are smaller and of low economic value. The exotic brown trout is established in some rivers and streams. Fish production in mountain streams is low and therefore commercial fishery is on a low scale only. Sport and recreational fishery targets the native mahseers Tor tor and Tor putitora, and brown trout. Organised brown trout fishing is confined mainly to the streams of Kashmir and Himachal Pradesh. Common carp, introduced in Kashmir and in the Kumaon Himalaya, is now a common fish in the Kashmir Valley lakes and the Jhelum River. Inadvertent introduction of silver carp has led to a decrease in the common carp and katla in the coldwater Gobindsagar Reservoir on the Beas River. If a better management of river fisheries is to be achieved, a better knowledge of fish stocks is needed. Protection and rehabilitation of some fish habitats is also needed. However, the future improvement in fish stocks will depend on regular stocking, as the presence of dams on many rivers and streams has stopped the migrations of mahseers and schizothoracines. Sport/recreational fishery is considered an important factor in the effort to improve the economic status of the mountain regions.
The Himalayas (Map) stretch for about 2500 km from west to east between Nanga Parbat (8126 m) in the west and Namcha Barwa (7756 m) in the east reaching their highest point in Mount Everest (8848 m). This mountain system is bordered in the west by the Hindu Kush and Karakoram mountains and in the north by the high Plateau of Tibet. The width from the south to the north varies between 200 and 400 km. Himalayas cover 594,400 km2.
From south to north the Himalayas are divided into four parallel and longitudinal mountain belts of varying width, each having distinct physiographic features and its own geological history. These four divisions from south to north are known as the Siwaliks, the Lesser Himalaya, the Greater Himalaya and the Trans-Himalaya.
The Himalayas are drained by 19 major rivers, of which the Indus and the Brahmaputra are the longest, each having a mountain catchment of about 160,000 km2. Of the remaining 17 rivers five belong to the Indus system, of which the Beas and the Sutlej have a total catchment area of 80,000 km2; nine (Ganga, Yamuna, Ram Ganga, Kali-Sharda, Karnali, Rapti, Gandak,
Bhagmati, Kosi) belong to the Ganga system, draining nearly 150,000 km2; and three (Tista, Raidak, Manas) belong to the Brahmaputra system, draining another 110,000 km2. Most of these rivers flow in deep valleys until they exit the mountains (Fig.1).
The deepening of the valleys and the elevation of the Himalayas took place simultaneously, resulting in the formation of mountain ranges with completely developed river systems. Different types of rocks and formations have resulted in rapids, cataracts, waterfalls, etc., which are common in the Himalayan chain of mountains. In the physiography of the Himalayas the forest or vegetation cover forms an important element. Sub-tropical, temperate and alpine zones of vegetation are encountered as one moves from sub-Himalayan tracts to the snowy ranges. The highest limit of forest growth in the more humid eastern Himalaya of Sikkim and Arunachal Pradesh is 4600-4900 m, and in drier Kumaon and Kashmir Himalaya the highest limit of tree growth is 4000-4200 m (Fig. 2). Beyond this altitude trees and shrubs disappear and the mountains assume a rugged wind-swept and frost-bitten character.
The Himalayan rivers Indus, Ganga and Brahmaputra are among the largest rivers in the world. Drainage area, sources and length of selected Himalayan rivers are given in Table 1. The mean annual discharge of 209,691.6 million m-3 of the Indus River is twice that of the Nile, and three times that of the Tigris and Euphrates combined (Gulhati, 1968). The principal rivers of the Indus system being snow-fed are all perennial but the flow in them varies enormously during the year. Floods occur in the rainy season (July-September), while the discharge is minimal during winter, although occasional freshets occur. Unlike many other rivers of the world, the Indus and its tributaries receive all their water in the mountain region of their catchments. The flow characteristics vary from one river to another in the Indus system. In the main Indus, the discharges are lowest from mid-December to mid-February. The Jhelum and the Chenab have a winter minimum from mid-November to mid-January while in the Ravi, the Beas and the Sutlej the minimum is from mid-November to mid-February. The peaks occur from July to September. The seasonal variations in flow of these rivers are given in Table 2.
The Ganga has five source rivers, viz. the Bhagirathi, the Mandakini, the Alaknanda, the Dhauliganga and the Pindar (Fig.3). The combined waters of the Alaknanda, the Dhauliganga and the Pindar join the Bhagirathi at Devaprayag to form the Ganga which emerges from the mountains at Rishikesh and flows down to Hardwar and to the northern plains of India.
The Brahmaputra, known as Yarlung Zangbo Jiang (Tsangpo) in Tibet, enters India under the name Dihang in Arunachal Pradesh. At its border with Assam it is joined by the Dibang and the Lohit, and from that point, turning west, the river is known as the Brahmaputra. The river carries clear water with little silt in Tibet, but on its entry into India the silt load increases. The river causes heavy floods during the south-west monsoon season (Fig.4).
The fish species distribution in the Himalayan streams depends on the flow rate, nature of substratum, water temperature. and the availability of food. In torrential streams Sehgal (1988) identified several zones on the basis of dominant fish species and the hydrographical features: (i) headwater zone inhabited by rheophilic species of loaches and catfishes (Noemacheilus gracilis, N. stoliczkae and Glyptosternum reticulatum); (ii) large stream zone, formed by the joining of headwater streams, inhabited by Diptychus maculatus and
Noemacheilus spp. In the upper reaches or the most torrential reaches of this zone, rheophilic species of the snow trouts Schizothoraichthys esocinus, S. progastus, Schizothorax richardsonii and Schizopygopsis stoliczkae occur. The intermediate reaches of the large stream zones are frequented by Schizothorax longipinnis, S. planifrons and S. micropogon. The least rapid reaches of this zone are occupied by Garra gotyla, Crossocheilus diplochilus, Labeo dero and L. dyocheilus; (iii) slow moving meandering zone inhabited by a large number of cold- to eurythermal species such as Barilius spp., Tor spp. cat fishes, homalopterid fish (Homaloptera spp.) and snakeheads (Channa spp.).
Menon (1954) related the distribution pattern of Himalayan fish to morphological characteristics which enable them to inhabit the torrential streams. He recognised six major groups: (a) fish dwelling in shallow, clear cold waters in the foothills without any striking modifications to current: Labeo, Tor, Barilius and Puntius; (b) fish inhabiting the bottom water layers in deep fast current, with powerful muscular cylindrical bodies: schizothoracines and the introduced trouts; (c) fish sheltering among pebbles and stones to ward off the strong current: Crossocheilus diplochilus; (d) fish sheltering among pebbles and shingles in shallows, with special attachment devices: the loaches Noemacheilus, Botia and Amblyceps; (e) fish which cling to exposed surfaces of bare rocks in slower current, with adhesive organs on their ventral surface for attachment to rocks: Garra, Glyptothorax and Glyptosternum; and (f) fish which cling to the exposed surfaces of bare rocks in fast current, with limpet-shaped bodies and mouth, gills and fins highly modified to suit the habitat: Balitora.
Hora (1955) and Menon (1962) studied the evolution of schizothoracines and concluded that they appeared during the first interglacial period, when turbulent streams formed in Central Asia, necessitating the reduction of scales which is characteristic of schizothoracines. Primitive forms of this group occur today in South China. During the favourable environmental conditions of the second glacial period they migrated westwards as far as Kashmir and Sistan. The great proliferation of genera and species of the sub-family Schizothoracinae probably occurred during the second and subsequent interglacial periods. Today the schizothoracines are mainly Central Asiatic in distribution although a few species are present also along the southern
face of the Himalayas. This is perhaps on account of the Trans-Himalayan origin of some of the major rivers like the Indus, the Sutlej and the Brahmaputra, which made it possible to descend to the lower reaches of these rivers.
The eastern Himalaya drained by the Brahmaputra has a greater diversity of coldwater fish than the western Himalayan drainage. For the whole Himalayas, 218 species are listed (Menon, 1962). The subsistence and commercial fisheries exploit carps (Labeo and Tor spp.), lesser barils (Barilius spp.), schizothoracines (Schizothorax and Schizothoraichthys spp.), garrids (Garra spp.) and sisorids (Glyptothorax and Glyptosternum spp.). The other genera are small-sized and of low economic value. The exotic brown trout (Salmo trutta) has established itself in some areas of the Himalayas.
The main factors which influence fish life in the Himalayan streams are: (i) current velocity; (ii) fluctuation in water discharge; (iii) water temperature and dissolved oxygen level; (iv) substratum; (v) shelter from the current; and (vi) food availability represented mostly by organisms clinging to and growing on rock and stone surfaces in fast current.
The Himalayan fish spend the major part of their life facing the current. This helps them in two ways: firstly, to maintain their upright position, and secondly, to make respiration easier. They have to open their mouths to take in water and boost the respiratory current. Shoals of lesser barils (Barilius spp.) are present in shallow pools (20-25 cm in depth). Loaches, which have coloration of their backs matching the background of sandy pools, swim rapidly in short bursts.
The need for shelter from the current has led to territoriality. Mahseers and schizothoracines chase intruders to defend the limited food resource and available shelter. Such a behaviour develops after the young fish emerges from the eggs laid in gravel. During winter months all size groups of mahseers and schizothoracines are present in pools when the water level is at its lowest and water is highly transparent. Such pools are present in the rivers Jhelum, Beas, Sutlej and Yamuna (Sehgal, 1988). Shoaling behaviour is seen in lesser barils and juvenile mahseers in shallow pools of the principal tributaries of the rivers Beas, Sutlej and Yamuna. This is one of the devices employed by these species to confuse predators. When a few fish are caught in a cast net, the rest disperse.
Water temperature is always an important limiting factor affecting geographical distribution and local occurrence within one water system. Cold stenothermic species such as the endemic schizothoracines (Schizothoraichthys esocinus and Diptychus maculatus) and exotic brown trout have an upper tolerance around 20°C. Carps, mahseers and lesser barils have a wider tolerance and even survive water temperatures over 25°C. Schizothoracines and brown trout remain active in the near-zero temperature which prevail in streams of the Lesser and Greater Himalaya during December and January. Hailstorms and drought conditions in the Lesser Himalaya may cause adverse conditions. A drought during 1972 in Kashmir resulted in trout kill due to the sharp rise of temperature in the Vishav River, a tributary of the Jhelum in Kashmir Valley (Sehgal, 1970).
To cope with the steep fall in temperature in winter months schizothoracines migrate from headwaters to lower altitudes where they represent a sizeable part in fish catches in large rivers and their tributaries. The rise in temperature in Kashmir streams from near-freezing level to 10-17°C during May-June induces S. richardsonii, S. longipinnis and S. curvifrons to spawn. In the Sutlej River, S. richardsonii starts upstream migration with the rise in water temperature during March. During the upstream migration the fish still finds itself in waters of low temperature of 8.0-9.5°C, owing to the steady influx of snow-melt water. This induces the species to migrate to and spawn in side streams, which receive warm ground water of 17.5-21.5°C. In the Ravi River system the fish spawn in May. In the upper Beas, however, the fish spawn only in July-August when the stream water temperature warms up to 16.5-18.5°C. In the same drainage S. richardsonii migrates downstream to the lowermost reaches where it spawns from October to December at 19.0 to 22.5°C. These observations indicate that in some schizothoracines multiple spawning is determined by temperatures and flow rates optimal for egg laying. The eggs are large-sized (3.0-4.0 mm diameter) and sticky in nature. They are laid in shallow pools (50-70 cm depth) and remain adhered to the substratum until the hatching of fry.
The fast-swimming species of mahseer, trout and schizothoracines expend much energy in maintaining an upright position in the turbulent and fast current. An attempt has been made to classify the coldwater fish on the basis of current velocity in the Jhelum basin of Kashmir (Sehgal, 1988). Table 3 gives distribution of the principal coldwater fish of Kashmir in relation to the source, elevation and current velocity. The frequent occurrence of spates has proved deleterious to breeding and propagation of coldwater fish. The scanty population as indicated by the low density of fish in the upper reaches of the Sutlej and Chenab rivers may result from the passage of these rivers through deep and narrow gorges, and the presence of cold glacier- and snow-melt water.
The fluctuating discharge of water and drying out of streams, leaving only isolated pools or no water at all, is another important matter. A study on seasonal fluctuation in river discharge in the Indus system (Gulhati, 1968) indicates that the range of mean flow from October to March (winter months) represents only 8-10% of the total annual flow. There are also variations from year to year depending on the winter and monsoon precipitation. Reduction of torrential streams to stagnant pools exposes the fish to terrestrial predators and to depletion in dissolved oxygen concentrations, especially when autumn leaf fall takes place. However, due to low temperature, the level of dissolved oxygen may not fall below the optimum required by coldwater fish (7.0-8.0 mg l-1). As soon as the flow is restored with spring rains and snow-melt water a rapid recolonisation of the stream takes place.
In the Himalayas, two zones can be distinguished. The rhithron zone is characterized by a monthly mean temperature of 17.3°C, high concentrations of dissolved oxygen (l0.l mg l-1), fast current (0.9-1.8 m/sec), and turbulent waters. The substratum is rocks and boulders with sand and silt patches and with some pools. The fish of this zone are stenothermic, such as brown trout and snow trouts (S. richardsonii, Schizothoraichthys esocinus and S. progastus). This zone borders on the potamon zone which has a higher mean water temperature of 22.1°C, dissolved oxygen of 8.0 mg l-1, and current velocity of 0.5-0.7 m/sec. The substratum consists of boulders, stones, gravel and patches of aquatic vegetation in the pools. The fish fauna is eurythermic or warm-stenothermic (Labeo dero, Tor putitora and Garra gotyla).
There is no firm separation of these two zones. As a result of a study of eleven rivers in the northwestern Himalayas, Sehgal (1988) showed that a gradual increase in water temperature and pH corresponds to a decrease in dissolved oxygen, decline in the density of nymphs of mayflies and stoneflies, but in an increase in larval and adult aquatic beetles. He also noted the changes in the prevalent fish species (Table 4). Sehgal (1988, 1989) also gives some information on water quality for the eleven rivers, i.e. Indus, Jhelum, Chenab, Ravi, Beas, Sutlej, Jamuna, Bhagirathi, Alaknanda, Mandakini and Pindar. The information collected during expeditions is based on spot measurements and it does not represent average values. The following ranges for the 11 rivers were recorded: current velocity (cm/sec): 0.6-1.2; transparency (cm): 4.2-33.7; pH: 7.1-7.8; water temperature (oC): 9.0-19.0. For the following chemical components the values are given as mg l-1: dissolved oxygen: 7.6-11.2; total alkalinity: 50.3-202.2; chlorides: 4.0-12.5 (the highest value measured in the Indus, representing twice the value of the next highest); silicates: 0.5-1.25; calcium: 1.2-1.9.
Fisheries in the Himalayan rivers can be divided into (a) subsistence fishery; and (b) sport/recreational fishery. Fish production in mountain streams is low and therefore any commercial fishery is on a very limited scale. The low biological productivity results in the prevalence of small-sized fish, except in pools where fish have some shelter and resting place.
The fishing methods using nets, traps and poison are simple but well-suited to the turbulent nature of the streams. Cast nets of 1.0-2.0 m diameter, with mesh sizes 1.2 to 3.0 cm bar to bar and sinkers of a total weight of 5 kg, are the most common gear used. The sinkers allow rapid settling of the net at the bottom, thus preventing it from being carried downstream by the rapid current. The fisherman upturns the stones on the stream bed covered by the net, which makes the fish come out of their hideouts below the stones and get trapped in the peripheral pockets of the net. The other types of nets used are: drag nets operated in conjunction with stake net (kadh), seines, stake nets, bag nets (kochbi), and some other types. The traps (chip and urli) are typical for Himachal Pradesh: the whole stream is usually diverted into this trap.
The various poisons used are lime, sap of Euphorbia rogleana, powdered seed of Xanthoxylum alatum and Cascaria tormentosa, boiled tea leaves, etc. In addition, spears, horse hair nooses, harpoons with 4-5 barbed points and grain fishing are also used in different waters of the Himalayas.
3.1 Fish catches and species composition
Experimental fishing in the northwestern Himalayan rivers using cast nets of 1 m diameter recorded a maximum catch in the River Jhelum in Kashmir Valley (Sehgal, 1988). This river meanders (Fig. 5), which indicates its slow flow, and it thus represents a favourable habitat for the common carp (Cyprinus carpio). In the River Jhelum the CPUE (one fisherman with one boatman, both in one boat) ranged from 302 g to 828 g per hour (Sunder and Subla, 1984). The catch comprised mainly schizothoracines (24.6 to 100%) and common carp (1.2 to 70%). Large numbers of schizothoracines were captured during winter months (December-February), probably on account of their downstream migration to avoid extremely low water temperatures of the winter season. Common carp catches increased with the onset of summer, reaching the peak in June-July. This species is absent from the other ten rivers of western Himalayas. The CPUE improves in all rivers when they meander through the Siwalik Himalayas. In the River Gola during 1988-89 the CPUE from 50 castings with a standard net (mesh 2.5 cm knot to knot) in one kilometre stream length ranged from 80 to 610 g/man/hour.
In the northwestern Himalayas eight species of fish are considered to be of commercial importance (Sehgal, 1988). The species composition of a sample netting included Schizothoraichthys esocinus (6.8%), Schizothorax richardsonii (64.0%), Tor putitora (3.9%), Labeo dero (3.7%), L. dyocheilus (0.2%), Barilius bendelisis (5.2%), Garra gotyla (5.7%), Crossocheilus diplochilus (2.0%). S. esocinus contributed 53.2% in the Indus River, followed by 21.9% in the Jhelum. It ranged from 310 to 510 mm in total length and 1l8 to 500 g in weight. The widely distributed Schizothorax richardsonii was caught in all 11 river systems. This species also contributes to the fisheries in the Lesser, and to some extent in the Greater Himalaya. In the lower reaches it is fished especially during the winter. Its size varies from 89 to 453 mm in total length and 120 to 450 g in weight.
Golden mahseer, Tor putitora, is a migratory fish. This important sport fish migrates from the lower to the middle reaches to spawn. It is a multiple spawner. There is, however, one principal spawning season during the time when streams swell with the southwest monsoon precipitation. In snow-melt receiving tributaries of the Beas River T. putitora spawns twice a year (Sehgal, 1974): in April-May when these tributaries receive freshets from the snow-melt, inducing the local stocks to spawn; and in August-September when it spawns during the onset of heavy monsoon floods.
This fish has suffered badly in the hands of poachers through indiscriminate fishing. During 1964-67 the catches of Tor putitora in the Baner, the main snow-melt tributary of the Beas, by a trap called chip showed a downward trend. This trap was operated by the total fishing community of Kangra, Himachal Pradesh, during September-October every year, when the spent spawners which had migrated earlier from the lowermost reaches for spawning, returned. Hardly any fish coming downstream escapes from such a kill. Within three years, the fish catch declined in two such traps from 1383 kg in 1964, when Tor putitora represented 39.2% of the total, to 54 kg in 1967. In another case study in the same stream fishing with a drag net in conjunction with a stake net during winter months also led to a gradual decline in
catches of golden mahseer. Further damage to mahseer stocks has been inflicted by dams and weirs which have stopped fish migrations. There is hardly any efficient fish pass or lift provided in any of these projects (Natrajan and Sehgal, 1982). Use of explosives and poisons are the other methods which have brought sharp depletion of mahseer in the Himalayan waters. Increased soil erosion, resulting from deforestation of mountains, has led to heavy siltation of rivers and streams, thus impairing the basic ecological requirements of mahseer.
3.2 Sport and recreational fishery
In India angling has remained a favourite pursuit of the British in the first half of this century, and it was mainly for this reason that brown trout and rainbow trout were introduced in the upland waters. In India sport fishing is now a very popular outdoor recreational activity which has given boost to tourism in the Himalayas. The best sport fish are Tor putitora, Tor tor and brown trout. One can expect that with fast increasing urbanisation in the country, recreational fishery will become even more popular as a means of escaping the crowded conditions of towns.
Trout
The trout, which is now acclimatised in the streams of Jammu and Kashmir, Himachal Pradesh and to a lesser extent in the central and eastern Himalayas, is permitted to be caught on rod and line using both artificial and live baits. Special bylaws have been formulated under the Indian Fisheries Act in the states of Jammu and Kashmir and Himachal Pradesh. They regulate the fishing season, bag limit and prescribed baits.
Organised brown trout fishing is confined mainly to the streams of Kashmir and Himachal Pradesh in the northwestern Himalayas. As per fishing regulations, `dry and wet' fly spinning, artificial and natural worms, etc. are the allowed baits for brown trout fishing. The artificial spinning bait, however, has been banned in Kashmir waters since 1970 (Sehgal, 1987). The larger rivers Sindh, Lidder and Kishenganga, are foaming torrents during May-July and are said to give the best fishing with `wet' fly and weighted casts. Bringhi and Erin flies are generally the rule, and `wet' fly fishing is good throughout the season. In the spring-fed small streams such as Verinag and Kokernag `wet' and `dry' fly fishing gives excellent results. In Himachal Pradesh every method of sport fishing is permissible under the bylaws. In Kashmir all trout streams are divided into fishing beats, each with a stream length of 3-5 km. The number of anglers to be permitted in each beat is fixed on a daily, weekly or seasonal basis. The fishing season extends from March to October every year. The minimum legal size of trout to be caught from any of the Himalayan streams in Kashmir and Himachal Pradesh ranges from 25-30 cm. The bag limit ranges from 5-7 fish of 25 cm and above in length. The number of undersized fish caught by each angler is to be retained in Kashmir but returned in Himachal Pradesh and recorded in the log book. However, there are very few anglers who follow such instructions.
The published data on creel census of brown trout fishing indicate deterioration in catches throughout the northwestern Himalaya. According to Crowe (1955) and Macdonald (1955) the percentage of fish below 25.0 cm/400 g hooked by them in Kashmir streams was 66.0-100.0% But during 1971-74 70-75% of trout catches remained below the legal size. During 1969-72 the Sindh and Lidder streams of Kashmir had 75% of angled brown trout under 200 g; 21% from 200 to 400 g; and 4% from 400 to 500 g (Kumar, Sehgal and Sunder, 1982). These authors recorded a 79.0% decline in the number of rods operated; 92% decline in the trout caught; 91% in average total weight; 68.4% in average number/rod; and 63.9% in average weight of individual trout.
Mahseers
The principal species of mahseers which contribute to the sport fishery are Tor putitora, T. tor and T. mosal. These species have wide-range distribution in the Himalayan rivers. They are caught on a stiff fibreglass rod of 3-4 m in length which has an adjustable brake system reel and a 4.5-5.4 kg strength line. Five principal ways of fishing for mahseer are: spinning, fly fishing, live-bait fishing, gram fishing, and paste fishing. The fishing starts when the stream water is cleared of silt after monsoon floods. On the southern face of the Himalayas, the recommended period for fishing in the foothills is from February-May and September-November. The optimum hours of fishing are before 9.00 am and from 16.00 pm till sunset. The mahseer is a sight feeder and hence, immediately after sunset they cease running at a spinning bait although they may take night lines.
The various species of mahseers are primarily inhabitants of the mountain sections of the principal rivers of India. They are rarely in areas where a river meanders and has a sandy bed, but are found in deep, still pools. The fish congregate in deep runs, especially where a fall enters a pool and in the eddies of these runs. It is better to fish in the runs, the best area being the middle portion of each run. The still, deep pools are equally good and can be approached by bloated buffalo skin locally known as surmai or a fibreglass boat.
In the past there was a sharp decline in catches of the mahseers, which are declared endangered fish in India. However, a number of angling associations have made an effort to create awareness among the fishing community and devoted anglers in particular, to conserve the threatened genetic material in the Himalayas. The same two expeditions which searched for mahseer in the Western Ghats (see Sehgal, this volume) also visited the Himalayas. The Trans World Fishing Expedition (TWFE) during 1977 spent nearly 4 months in its quest for the mahseer, but it caught only small-sized fish of 1300 to 1700 g in the Himalayan rivers. The mahseer mission of Mr. Paul Boote spent nearly six months on fishing in the Indian rivers (Boote, 1979). In the Himalayan region the size of fish hooked ranged between 2 and 3 kg. In 1980-82 the largest fish hooked in the Beas were 5 to 13 kg. The angling association, in collaboration with the Government of Himachal Pradesh, has made a 70 km stretch of the Beas an assured Tor putitora fish belt (Sehgal, 1987).
In the eastern Himalaya, the North Bank Shooting Fishing Association has been organising annually one-day angling competitions since 1981. As per the data published in l990, the largest Tor putitora recorded in these streams was 21.6 kg in the River Subansiri.
In the Himalayas as in many other parts of the world several exotic species have been introduced without any consideration of the impact of such introductions on the endemic fish. Brown trout and rainbow trout were introduced to meet the requirements of sport fishing for the British who settled in India in the l9th century. In the absence of any fast-growing endemic species in cold waters, common carp was introduced into aquaculture. In the beginning such introductions remained limited to certain areas. Subsequently, these species were transferred to every suitable area of the Himalayas without taking into account the justification for such introductions, the interaction of the introduced fish with other members of the ecosystem and the role played by parasites and diseases. The third species, the silver carp, which accidentally got transplanted into the River Sutlej, is another matter of controversy.
Five species of salmonids were introduced in the Himalayas between 1905 and 1969 from Europe, North America and Canada. These were: brown trout, rainbow trout, eastern brook trout (Salvelinus fontinalis), splake (hybrid between lake and brook trouts), and the land-locked variety of Atlantic salmon (Salmo salar). Of these, brown trout is now well established, with a number of self-sustaining populations in the streams of the Himalayas. Rainbow trout has failed to establish itself in the stream ecosystem but it is cultured in fish farms.
An opinion prevails that a sharp decline in catches of schizothoracine species in the Himalayas is the result of brown trout preying upon their younger stages. Schizothoracines, notably Schizothoraichthys esocinus, S. progastus, Schizothorax richardsonii, S. longipinnis, S. nasus and S. hugelii are the most important endemic species of fish occurring in the Himalayan trout waters. These rather small fish range from 200 to 450 mm in total length and from 300 to 1200 g in weight. The fish may spawn in several batches. The main spawning, however, takes place when the stream water reaches temperatures of 10.0-21.5°C. The average fecundity is 30,000-40,000 eggs per kg body weight. The brown/rainbow trouts release all the eggs in a single stroke and fecundity ranges between 1800-2500 eggs per kg body weight. The two groups of coldwater fish differ considerably in their feeding habits. The various species of schizothoracines feed mainly on microbiota growing on bottom stones and rocks with a rasping action of the ventrally-placed mouth. Some of the associated smaller, soft-bodied insect larvae also find their way into the gut. While investigating the impact of the Beas-Sutlej Link on limnology and fisheries of the River Beas, Sehgal and Sar (1989) and Sehgal (1990) studied the food preferences of brown trout and Schizothorax richardsonii. Brown trout of 100-200 mm consumed principally nymphs of mayflies (74.2% of the total food taken), followed by the larvae of caddisflies (13.7%), Diptera (7.9%), and miscellaneous items (4.2%). The same size group of S. richardsonii consumed green algae (54.2%), followed by blue-green algae (44.6%) and miscellaneous items (1.2%). Based on feeding habits and the mode of reproduction hardly any competition was observed between the two species. Shah and Raizada (1977) in data based on 1965 records noted that the average size of brown trout was 260 g against 300 g for S. richardsonii. During the 1985-87 experimental fishing in the Beas the average size of brown trout and S. richardsonii was 88.0 g and 256 g respectively (Sehgal, l990). These observations reveal that perhaps brown trout has suffered the most during the last 22 years and the decline in average size for this species is 172 g as against 40 g for snow trout. The decline in average size may be attributed to the increase in angling pressure and the fast degradation of the ecological conditions of the river system. These observations, however, do not confirm the suggested adverse impact of brown trout on endemic species. More investigations are needed in order to fully clarify the interrelationships between brown trout and schizothoracines in the Himalayan streams and rivers.
The introduction of common carp in Kashmir and in the Kumaon Himalaya is also debated in connection with its potential impact on schizothoracines. 500 fingerlings of common carp were released in Lake Dal in 1956. Since then the species has spread throughout the Kashmir Valley lakes and slowly flowing rivers. Das and Subla (1970) reported a sharp increase in common carp catches in Lake Dal, with the once abundant schizothoracine species having been virtually ousted. It is believed that the endemic schizothoracines are fast losing their ground in Kashmir lakes due to the higher fecundity of common carp and its habit of spawning in confined waters (Sunder et al., 1979). By contrast, schizothoracines undergo breeding migration for spawning in turbulent streams, and they also have a lower fecundity than carp. The feeding pattern of common carp and schizothoracines is almost identical, with many of the lacustrine species of schizothoracines feeding on detritus and benthos. In the Jhelum River in Kashmir schizothoracines represented 78% of the total catch during 1980-82 (Sunder and Subha, 1984a). In Gobindsagar Reservoir (Fig. 6) common carp contributed 22-35% to the total catch between 1975 and 1984, but with the increase in silver carp there was a decline in common carp (Kumar, 1988). Due to their high fecundity, silver and common carps have monopolised the whole water body. According to Kumar (1988) the exotic carps in Gobindsagar have increased annually at a rate of 8.2% for the last 14 years. This may be attributed to various factors like distortion of ecology of such waters as a result of natural and man-made causes and destruction of spawning grounds and diversion of stream water. It will, however, be necessary to undertake detailed investigations on the biology of the two species in selected waters to further clarify the silver carp-common carp-mahseer-schizothoracines interrelationships. In spite of the common carp being the most common food fish in the Himalayas, schizothoracines are still the consumer's first preference.
The first introduction of silver carp in the Himalayan waters was an accident. About 47 specimens of silver carp found their way into the Sutlej River in Himachal Pradesh in 1971 when floods inundated the Deoli fish farm located on its bank near the tail end of Gobindsagar reservoir. The species has since established itself in the reservoir resulting in the formation of a self-sustaining population. The fish entered the catches in 1976. By 1987 silver carp represented 65.8% of the total catch. Due to poor keeping quality, the species though rated `A' production-wise is `C' grade in consumers' preference. This has brought economic losses to the fishing community. As a fish which feeds largely on phytoplankton silver carp has a biological advantage over the Indian carp katla (Catla catla), a column plankton feeder. Silver carp also matures earlier than katla. Silver carp now outnumbers katla in this reservoir.
Over the years uncontrolled and often indiscriminate fishing in the largely unmanaged Himalayan rivers and streams has resulted in a sharp decline in catches of the important sport and subsistence fish. The increasing use of river water for irrigation, hydropower production, municipal and industrial purposes, and the inputs of pollutants, have also impacted on fish stocks. Among the difficulties that fishery managers are facing today is the shortage of data for a number of rivers and even whole areas of Himalayas. Information is available on limnology and fisheries of certain stretches of streams traversing the northwestern and central Himalayas but there is hardly any information on the ecology and fisheries of rivers of the eastern Himalaya. The most essential requirement is to estimate the resources which would enable the fishery scientists and planners to formulate a management policy. Another, and an increasingly important aspects, is the need to evaluate the environmental impacts caused by human-induced changes in river and lake catchments, and how these have contributed to the decline in fish stocks. The use of destructive methods of fishing calls for effective enforcement of legislative measures and for education of the fishing community. There is a need to improve the surveillance along the rivers in order to protect fish stocks. In this respect the role of voluntary agencies in conserving stocks must not be underestimated.
During the 1970s and 1980s studies of the Himalayan streams in the northwestern, central and eastern Himalayas showed that a variety of human impacts had resulted in changes in benthic productivity, fish community structure and fish yield. The impact of ecological changes as a result of human and natural stresses was investigated in a case study of the River Beas between 1985-87. There were changes in water temperature, current velocity, total alkalinity and silicates concentrations. Among the benthic invertebrates there was a decline in the density of stonefly and caddisfly larvae, and in the aufwuchs community on stones, as compared with pre-impoundment conditions (Sehgal, 1990). This probably also contributed to the changes in brown trout and rainbow trout. The average weight of brown trout in the River Beas declined from 260 g in 1964-65, to 87 g during 1985-87 (Shah and Raizada, 1977). The average weight of S. richardsonii also declined from 300 g in 1965 to 260 g in 1985-87.
The study on the Beas River further revealed considerable impact of water abstraction on aquatic life below the dam. The diversion of the Beas water to the Sutlej River brought nearly 61% reduction in water discharge and an increase in water temperature by 4oC. The reduction in water discharge resulted in an increase in benthic microbiota. Among the benthic invertebrates there was a sharp decline in the density of stonefly nymphs as a result of the sharp reduction in current and increase in water temperature. Fortunately, the Beas below the dam at Pandoh receives a major right bank tributary, the Uhl, at a distance of about 10 km from the dam. The water volume in the Uhl at this point is about equal to that of the Beas and as a result, after the confluence of the Uhl with Beas, the situation returns to normal.
In the central Himalaya, large and medium-sized dams on the Chenab at Salal and on the various source rivers of the Ganga at Tehri, Rudraprayag, Vishnuprayag and Lachmanjhula, are likely to have an impact, especially on the mahseers and schizothoracines. As stated earlier the schizothoracines undertake migration from upstream to downstream at certain times of the year. Any obstruction on their migratory routes will adversely affect the winter fishery for these fish in the lower reaches of these rivers. A dam on the Beas resulted in a reduction in the proportion of mahseers and schizothoracines in the winter catches between Mandi and Nadaun, from 10.2-13.5% in 1964 to 1.0-0.5% in 1985-87. Tor putitora, which used to migrate in the Beas up to Sultanpur, Kulu Valley, prior to completion of the Beas dam, now cannot proceed upstream beyond Pandoh. The Juni tributary, which used to be the main spawning ground of Tor putitora at Pandoh, has disappeared as a result of the accumulation of debris (Sehgal, 1990).
Fish ladders constructed on several weirs and barrages to facilitate migration of Tor putitora and other carps were found ineffective. The drawbacks of these fish ladders are their steepness and then narrow and inconspicuous inlets. These ladders were found to function as fish traps and as such used by poachers. A high dam on the River Sutlej at Bhakra resulted in a sharp decline in catches of Tor putitora in Gobindsagar reservoir from 40% in 1966 to 0.5% in 1979 (Natrajan and Sehgal, 1982). But this was later followed by an increase in catches of this mahseer, indicating that mahseer has found a way to produce new stocks under the new situation (Kumar, 1988).
While the creation of a reservoir results in the creation of a new habitat for fish, at the same time many endemic species are adversely affected. To resolve this problem, priority should be given to the preservation of the diminished stocks of riverine fish species. This should include enforcement of legislative measures such as closed season and mesh size regulation, and also the involvement of voluntary organisations, including fishing associations and clubs, in an effort to maintain the fish stocks at a healthy level. The stocks should be enhanced through regular releases of hatchery-produced fingerlings. Only in this way can the rising demands from subsistence and sport/recreational fishermen be satisfied. A programme of stream improvement to maintain optimal conditions for coldwater fish, is also needed, especially where such streams have been impacted by dams, channelization and pollution.
The age-old practice in India of imposing religious taboos on certain stretches and pools of important streams has undoubtedly helped to preserve mahseers and schizothoracines. Selected stretches of streams and rivers, pools and temple springs in the states Kashmir, Himachal Pradesh and Uttar Pradesh act as coldwater fish sanctuaries in the Himalayas. The practice of protecting fish stocks of brown trout and schizothoracines in Kashmir streams during the low water level period by creating deep pools, covering them with tree branches and protecting them from poaching, also has proved beneficial. The best way of improving the trout fishery in rivers and lakes is to regularly stock the waters with yearlings produced in hatcheries.
Better estimates of the carrying capacity of different streams would assist the fishery managers to better regulate sport and recreational fishing and to determine stocking rates. To meet the ever increasing demand for trout fishing in the Himalayas the authorities are enforcing a reduction in bag limit and closing of certain streams for fishing for some years. A study on the recapture of tagged fish is needed to estimate the percentage return of stocked fish.
There is also need to improve infrastructure for recreational and sport fishermen, as this would attract more tourists to the areas. Already such facilities exist in some parts of Kashmir and Himachal Pradesh. Permanent stocks of brown trout are now established in the Himalayan streams of Himachal Pradesh, Kashmir and Uttar Pradesh. At present Kashmir has 273 km of streams available for trout fishing, Himachal Pradesh 184 km, and Uttar Pradesh 150 km. It is common knowledge that fishing tourism improves the economic status of a region. A case study on economic benefits of sport fishing for mahseer/trout in Himachal Pradesh (Sarin, 1979) estimated that every international angler spends about US $ 200 per week, as compared to US $ 30 spent by a local angler.
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