13. BIHAR

Bihar is a land-locked State, stretching from the foothills of Himalayas in the north to Orissa in the south. The west is bordered by West Bengal and the east by Uttar Pradesh and Madhya Pradesh. The most striking geographical feature of Bihar is the sharp division between the north and south. North Bihar is an almost entirely level tract comprising the Ganga, its tributaries on either side and the maze of floodplains and wetlands. This alluvial land is extremely fertile, watered by the Sarayu, the Gandak and the mainstream Ganga. Southern Bihar, especially in and around the districts of Chhotanagpur and Santhal Parganas, is thickly wooded and consists of a succession of hills. The altitude varies from 300 to 1 300 m, the highest peak being 1 372 m above the sea level.

Palamu district is drained by the river North Koel, which joins the Son, a major tributary of the Ganga. The two main rivers originating in the Chhotanagpur hills and flowing down east are the Damodar and Subarnarekha. Both have been harnessed for irrigation and power generation. The Sankh, draining the Gumla district and the South Koel and Karo draining Gumla, Ranchi and Singhbhum districts are the tributaries of Brahmani, flowing to Orissa.

13.1 RESERVOIR FISHERIES RESOURCES OF BIHAR

Reservoirs, as a potential fishery resource, are yet to gain importance in Bihar. Documentation on reservoir fisheries resources in the State is not very comprehensive and exact, with the various estimates on the water area at variance with one another. Ahmed and Singh (1992) compiled a list of 105 reservoirs in the State, which is very close to the reality. Total area under reservoirs in the State is estimated at 96 695 ha (125 reservoirs), the share of small, medium and large reservoirs being 12 461 ha (112 reservoirs), 12 523 ha (5 reservoirs) and 71 711 ha (8 reservoirs) respectively. The landscape of Palamu district, with a large number of small streams radiating down to the North Koel, provides an ideal setting for small dams and 58 small reservoirs are situated in this district (Table 13.1). Ranchi, Monghyr, Bhagalpur and Gumla districts also have many small reservoirs. Large reservoirs (> 5 000 ha) are situated in Hazaribagh, Dhanbad (two each), Santhal Parganas, Gumla, Ranchi and Giridih (one each) districts (Fig. 13.1). Except the Latratu reservoir in Ranchi and Maithon reservoir in Dhanbad district, all the large reservoirs are in the <10 000 ha group.

Of the 125 reservoirs in the State, 112 (90%) are small and the water area occupied by them is only 13% of the total. The medium reservoirs also occupy similar percentage and thus 74% of the waterspread is under large reservoirs.

No major scientific studies on the reservoir ecosystems and their production functions have been done in Bihar, with the exception of the research conducted by the Central Inland Fisheries Research Institute in the Damodar Valley Corporation (DVC) reservoirs an Getalsud reservoir during the 1960s and 1970s respectively.

Figure 13.1. Distribution of reservoirs in Bihar

Compiled from Ahmed and Singh (1992), supplemented by data provided by the Director of Fisheries.

13.2 GETALSUD RESERVOIR (Fig. 13.2)

Getalsud reservoir is located at 23° 27' N and 85° 33' E, across the river Subarnarekha, 40 km east of Ranchi. Completed in 1971, the multi-purpose reservoir supplies water to Ranchi town, and for the industrial needs of the Heavy Engineering Corporation and other factories. The reservoir has a maximum surface area of 3 459 ha and a capacity of 288.5 million m³ at the FRL of 595.70 m above MSL. At the lowest level, the area is only 987 ha. River Subarnarekha, the main source of inflow, originates at Nagari, in the Chhotanagpur plateau of South Bihar, about 50 km upstream of Getlasud dam. Getalsud was studied by the CIFRI under the All India Coordinated Project on Reservoir Fisheries (Anon, 1984c).

The river has a total catchment area of 15 540 km². The local catchment receives rainfall of 100 to 1 198 cm. The reservoir has a shoreline of 80 km and the shoreline development index is 3.85. Maximum depth being 32.6 m, volume development index is less than unity (0.6839) and the mean depth is 8.46 m.

The air temperature at the reservoir drops down to 4.9 °C in winter and the summer temperature reaches 40.3 °C. These extreme variations in air temperature have an impact on the thermal regime of water. The winter water temperature is close to 16 °C and when the surface water starts heating up during summer, a thermocline is formed with a cool water layer in the depth. The temperature difference between the epilimnion and hypolimnion often reaches 7 °C. In 1980, the thermal discontinuity formed between 9 and 10 m with a temperature difference of 2 °C. The difference between the surface and bottom is 5.5 °C (Anon., 1984).

The bottom soil is acidic and poor in organic carbon (0.46 to 0.60 %). Available phosphorus and nitrogen are present in modest quantities (2.45 to 6.08 mg 100 g^-1 and 24.38 to 35.06 mg 100 g^-1).

Figure 13.2. Getalsud reservoir, Bihar

The morphometric and edaphic indicators of productivity and the estimates on the standing crop send conflicting signals on the status of the water body. A low shoreline development index and nutrient status in the water and sediment phases suggest oligotrophy, while the klinograde distribution of oxygen, accompanied by an increase in carbon dioxide towards the deeper layers clearly suggest high photosynthetic and nutrient releasing activities.

The river Subarnarekha receives factory effluents from the Heavy Engineering Corporation and sewage wastes emanating from the industrial township. A drop in dissolved oxygen, accompanied by decrease in plankton, has been reported below the discharge point. The water recovers its quality further downstream.

An average gross primary production of 289.8 and net production of 154.4 mg C m^-2 day^-1 have been reported in the lentic sector of the reservoir, compared to 257.85 and 137.12 mg C m^-2 day^-1 in the intermediate sector and 295.5 and 150.64 mg C m^-2 day^-1 in the lotic sector. The mean gross and net production rates are 281.07 and 147.4 mg C m^-2 day^-1.

Plankton

The moderately rich plankton community of the reservoir occasionally produces blooms. The mean density of plankton varies between 129 and 5 227 individuals 1^-1. During the blooms, it gmay reach 55 777 units 1^-1 (Table 13.2). The total plankton count in the lotic sector is higher than that of the lentic sector, suggesting a subdued production process at the main reservoir, due to lack of autochthonus enrichment. Good standing crop of plankton in the lotic sector is attributed to the effects of sewage effluent discharge into the upstream stretches of the river.

Numerically, phytoplankton contributes 72.1 to 94.6% to the total plankton in the lotic sector, 70.44 to 94.27% in the intermediate sector and 54.56 to 87.79% in the lentic sector. Diatoms have the maximum species diversity, followed by Chlorophyceae and blue- greens. Desmids and Dinophyceae (Ceratiumsp.) are also present. Zooplankton is represented by 12 genera of rotifers, 6 of protozoa, 5 cladocerans and 2 of copepods.

Benthic fauna

Bottom substrate in the lotic sector is soft and rich in organic matter, comprising decaying vegetation, but during monsoons, silt deposition is reported to blanket the organic matter. Density of benthic organisms is high in the lotic sector, their number attenuating towards the lentic sector. During 5 years of observations from 1975–76, abundance of benthic invertebrates varied from 353 to 1693 units m^-2 (average 978.4) in the lotic, 75 to 348 units m^-2 (average 217.2) in the intermediate and 81 to 168 units m^-2 (average 116.8) in the lentic sectors. Oligochaetes (Tubifex, Nais), Diptera (Culiocoides, Dixa, Chironomus, Chaoborus). Anisoptera (Aphylla), Trichoptera (Philopotamus) Coleoptera (Promoresia and molluscs (Corbicula, Pisidium, Goniobasis, Sphaerium and Gyralus, constitute the benthic macrofauna. Rich deposition of periphyton in densities ranging from 690 to 1 745 units cm^-2 has been reported on artificial substrata provided on experimental basis.

Forty-three species of fishes have been recorded from the reservoir. They include 24 species of Cyprinidae and 6 species of catfishes belonging to Siluridae, Bagridae, Clariidae and Heteropneustidae. Commercial fishing in Getalsud reservoir using gill nets was initiated by the Fisheries Department of the State Government in 1976–77 and continued up to June 1979. The reservoir was auctioned on 1st July 1979 for a period of 3 years.

* Figures within brackets indicate the maximum values recorded during the year

Fish and fisheries

The contractor deployed both gill and drag nets. Normally, four parties operate gill nets each having 4 men in one boat. The boats carry 40 nets, each measuring 30 m in length. A total of 4 800 m of gill nets in the mesh bar range of 70 to 150 mm are used. Major carps are mostly caught by the gill nets.

A normal unit of drag net, measuring 200 x 6 m, is operated by a group of fishermen with the help of a country boat. Drag netting, generally done during night between 2100 to 0400 hrs., is reported to be much more profitable in Getalsud reservoir, as large quantities of small fishes are caught.

Fishing is continued in the reservoir till the contractor is satisfied with the catch and thereafter moves his men and equipment to some other reservoir. The fish catch is brought to Ranchi and then handed over the retailers. As per information supplied by the State Fisheries Department, the commercial catch during 1976 to 1981 was in the range of 481 to 5 980 t (Fig. 13.3).

Figure 13.3. Fish catch (t) from Getalsud reservoir

Effect of impoundment on reproduction and recruitment

About 50 km upstream of Getalsud reservoir, the river Subarnarekha is dammed to form the Hatia reservoir. Jamuar, a tributary of the Subarnarekha joining the river between the dam and the confluence of Hatia, is also closed by a dam. When the southwest monsoon starts, the two upstream reservoirs discharge excess water towards Getalsud and this flowing water attracts brooders. However, they never reach breeding grounds and thus, the two dams above have an adverse effect on the spawning of fish in Getalsud reservoir.

Attempts to collect spawn from Jamuar were made in July and August during 1975 to 1979 and in 1981. The first indication of breeding of Gangetic major carps during the flood season was noticed during 1981, when 28.6% of the reared hatchlings were found to be Labeo calbasu and the rest minor carps. However, mostly, the spawn comprised fertilised eggs of minor carps and a few young ones of Cirrhinus mrigala. Bulk of the eggs, on rearing, turned out to be Cirrhinus reba. Operation of shore seines in trash various parts of the reservoir yielded hatchlings and fry of minor carps and trash fishes with no trace of major carps, indicating their poor recruitment.

Stocking

Stocking of Getalsud reservoir was initiated in 1974-75 and continued until 1980–81. During this period, a total of 3.35 million seed were stocked (Table 13.3). This included 120 992 minor carps stocked incidently. On the basis of average reservoir area, the stocking density was 203 ha^-1. Fingerlings numbering 2 680 of silver carp, Hypophthalmichthys molitrix were introduced into the reservoir in 1974. Based on the recovery of six specimens between 1974 to 1976, the growth of this fish was 715 mm and 4.5 kg in 866 days (Table 13.4).

The river Damodar used to be described as the sorrow of Bengal due to the frequent devastation it caused by flooding. Four impoundments were created on the river system under the Damodar Valley Corporation (DVC) for power generation during the 1950s, which moderated the flow regime. These four man-made lakes,viz., Konar, Tilaiya, Maithon and Panchet are collectively referred to as DVC reservoirs (Fig. 13.4). While Panchet is situated on the main river Damodar, Tilaiya and Maithon are on the tributarly, Barakar. Konar reservoir is on the river Konar, another tributary of the Damodar. The four reservoirs cover an area of 20 116 ha.

Figure 13.4. Damodar Valley Corporation (DVC) reservoirs, Bihar

THE DVC RESERVOIRS

13.3 KONAR (Fig. 13.5)

Completed in 1955, Konar reservoir covers 2 590 ha at FRL. The inflowing river Konar is a seasonal stream joining the river Damodar. Konar, has a catchment area of 997 km², comprising thick jungles, wastelands and cultivated areas. At FRL, the reservoir has a capacity of 336.16 million m³ and a mean depth of 12.97 m. The shoreline is 106 km long, the shoreline development index 8.78, volume development index 0.85. Basin soil of Konar reservoir is sandy loam to clay with 0.3 to 0.9% of organic carbon. The concentration of available phosphorus is a low 1.2 to 8.0 mg P₂O₄ 100 g^-1. Organic nitrogen of 0.069 to 0.101% is medium to high and pH of soil is acidic (5.4 to 6.0).

Water temperature of Konar reservoir varies from 17.8 to 28.9 °C (Ramakrishniah and Sarkar, 1982). Thermal stratification develops during summer (Natarajan, 1976). Winds prevailing during summer (5 to 8 km h^-1) can disturb only the epilimnetic layers which extend down to 9 m depth. A relatively stable warm hypolimnetic layer aids chemical stratification. While the inflowing floodwaters break the thermocline, the stronger monsoon winds of up to 11 km hr^-1 help the water circulation (Ramakrishniah and Sarkari 1982). Although depletion of oxygen is reported from the hypolimnion, stratification in terms of bicarbonates, free carbon dioxide and pH is not recorded.

Among the DVC reservoirs, Konar is the richest in ionic concentration. The total alkalinity varies in the range of 43.5 to 83.0 mg 1^-1 and specific conductivity within 81.20 to 147.6μmos during different seasons of the year. Nitrate (0.10 to 0.6 mg 1^-1) and phosphate (traces to 0.047 mg 1^-1) are high during the monsoon and post-monsoon months. Silicate (1.3 to 1.98 mg 1^-1) is, however, poor.

The planktonic abundance peaks during August, in conformity with many other Indian reservoirs. The plankton in Konar is characterised by a poor species diversity and an overwhelming dominance of Microcystis aeruginosa and Diaptomus sp. among the phyto- and zooplankton respectively. During the peak periods of abundance, the phytoplankton count goes up to 5 256 units 1^-1 in the intermediate sector of the reservoir. The highest density was recorded (3 570 individuals 1^-1) during the summer of 1973. Anabaena, Merismopedia, Botryoccocus, Spirogyra Oedogonium, Pleodorina,Ceratium andPeridinium are reported by Ramakrishniah and Sarkar (1982). Zooplankton comprises Difflugia, Arcella, Actinosphaerium, Keratella, Brachionus, Filinia, Polyarthra, Diaphanosoma, Ceriodaphnia, Cyclops and Diaptomus.

Figurev 13.5. Konar reservoir, Bihar

Construction of the dam and the consequent lake formation have brought radical changes in the fish composition. Prior to the damming, Konar was a torrential stream sustaining flood fisheries, such as minor carps and weed fishes. Job et al (1952) reported 12 species of fishes before the impoundment. During the post-impoundment phase, 20 additional species of weed fishes have established themselves in the reservoir. Most of them were probably introduced accidently with the stocking material. The absence of large predatory catfishes has resulted in low mortalities of these uneconomic species chiefly, Ambassis nama, Esomus dandrica, Oxygaster bacila, Amblypharyngodon mola, Osteobrama cotio, Puntius ticto, P. sophore and Barilius barna.

Fisheries management

Stocking in Konar reservoir was initiated in 1957 and continued until 1959. During this period, a total of 0.55 million fingerlings of Gangetic major carps were stocked. Virtually, no stocking of carps was done during the 1960s and 1970s, except the release of 125 000 fingerlings of catla (in 1968) and 64 000 mrigal (in 1970).

The annual fish production from Konar was 5.7 t in 1968, 2.4 t in 1969, 1.7 t in 1970 and 2.9 t in 1971 with corresponding yields of 3.6, 1.5, 1.1 and 1.1 kg. The constituent species were Catla catla, Cirrhinus mrigala Labeo calbasu, L rohita, L. bata, L. dyocheilus, Puntius sarana, Cyprinus carpio, Notopterus notopterus and Ompok bimaculatus, major carps contributing 90.54 to 94.76% of the catch.

There has been a decline in fish yield since 1968. The yield of catla declined sharply from 1.6 t in 1968 to 0.49 t in 1969, but improved to 1.1 t in 1970 and 1.8 t in 1971 as a direct result of stocking done in 1968. Jhingran and Natarajan (1969) rated the recruitment of catla as very feeble and felt that stocking on a continuous basis was essential. Mrigal showed a steep decline in the reservoir and its recruitment was described as moderate to poor. A similar decline in the stock of L. calbasu was noted, when the catch dropped from the level of 1.3 t in 1968 to 0.717 t in 1969, 0.2 t in 1970 and 0.3 t in 1971, due to an unsteady recruitment.

Jhingran and Natarajan (1969) estimated a catch net^-1 (15.25 m length, 4.25 m depth and 635 to 1270 mm mesh bar) of 0.353 kg and a total catch of 5.6 t during 1962–63. During the next two years, due to increased fishing effort (which included the fishermen deployed from Mettur), the catch went up to 23 t with a matching increase in catch per effort. However, in 1967–68, with a nearly identical fishing effort, the production fell to 10 t and the catch per unit of effort decreased to 0.226 kg clearly showing overfishing. Catla was the dominant component of catch, especially in the nets laid by the Mettur fishermen. By 1968, the total catch and catch per net decreased to 1 t and 0.075 kg respectively in the nets of Mettur fishermen. Nevertheless, the average weight of catla went up to 12.66 kg with a modal value of length at 900 mm (7 to 8 years old). The above observations confirm the belief that the stock of catla was thinning and the average size and age increasing. Changes in species spectrum over the years (1963-64 to 1967-68) indicate a decline in the populations of catla and an increase in C. mrigala (Table 13.5).

Fish carrying capacity of Konar was estimated at 40 kg ha^-1, which at biomass/yield ratio of 1.0 : 0.6, can yield 25 kg ha^-1 (Anon., 1968).

13.4 TILAIYA

Tilaiya dam, constructed across the river. Barakar was sealed in 1952. The reservoir has an area of 5 921 ha (Fig. 13.6) at FRL with a volume and mean depth of 394 million m³ and 6.65 m respectively. The shoreline is very irregular with a shoreline development index of 9.1. The volume development index is 0.766. The river rising from the hilly forests of Hazaribagh district, at an elevation of 610 m has a catchment area of 984 km², comprising mainly forests, pastures, cultivated land and wastelands. The annual rainfall in the area is 127 cm.

The bottom soil is acidic ( pH 5.6 to 5.9) and silty clay loam with low organic carbon (0.31 to 0.50%) and available phosphorus (3.0 mg P²O⁵ 100 g^-1). Organic nitrogen is in medium productivity range (0.073 to 0.101%). Water is rich in ionic concentration. Alkalinity (53.5 mg 1^-1) and specific conductivity (98.7 to 211 μmhos) are indicative of the the reservoir's proclivity to good organic productivity. Values of nitrate (0.25 mg 1^-1) and phosphate (0.03 mg 1^-1) are satisfactory. Gross primary productivity is estimated at 199 to 300 mg C m³ day^-1.

Species composition of the fish catch during 1960 to 1968 is detailed in Table 13.6. Gopalakrishnan et al. (1966) observed large-scale breeding of Indian major carps in the reservoir. Ramakrishniah and Banerjee (1979) estimated 11.30% of the total spawn collected from the breeding grounds connected with the reservoir to be that of L. rohita, C. mrigala and L. calbasu. Job et al. (1952) recorded 40 species of fishes belonging to 7 families in the river stretch before the impoundment. Among them, Labeo dero, Puntius chola, P. conchonius, Crossocheilus latitus, Garra mullya, G. gotyla, Macrognathus aculiatus, Oxygaster clupeoides and Aspidoparia morar have disappeared after the reservoir formation. The new species appearing after the reservoir formation include Notopterus notopterus, N. chitala, Wallago attu, Ompok bimaculatus, Rhinomugil corsula, Ambassis nama, A. ranga, Eutropichthys vacha, Labeo bata, Ailia coila, Mastacembelus armatus and M. pancalus.

Figure 13.6. Tilaiya reservoir, Bihar

In Tilaiya reservoir, 181 449 fingerlings of mrigal, 103 480 fingerlings of rohu and 27 211 fingerlings of catla were stocked in the year 1968. This heavy stocking did not have any impact on the fishery till 1970 and 1971, largely due to the formidable presence of the predatory catfish W. attu. Other predators such as Notopterus chitala and Barilius bola also were common in the reservoir. Experimental fishing carried out in Tilaiya showed that mesh bars 45, 50, 55 and 60 mm were very effective for catching W. attu and 30 and 35 mm for Barilius bola.

The total fish landing from Tilaiya reservoir was estimated at 9 t in 1968 (six months only), 13.4 t in 1969, 12.2 t in 1970 and 13.5 t in 1971. Species that figured prominently in the catch were C. catla, Cirrhinus mrigala, C. reba, Labeo calbasu, L. rohita, L. bata. L boggut, L. dyocheilus, Puntius sarana, Barilius bola, Wallgo attu Mystus cavasius, Aorichthys seenghala, Notopterus notopterus and Rhinomugil corsula. Among them, the share of major carps ranged between 57.54 and 76.61%. The fish yield rate from the Tilaiya was 3.6, 3.3 and 3.6 kg ha^-1 in 1969, 1970 and 1971 respectively.

The fishing effort in Tilaiya in terms of units of 15.25 m length of gill net was estimated at 55 477 units in 1969 and 69 660 units in 1970. The total catch per unit of effort was 241 g in 1969 and 170 g in 1970. The catla in Tilaiya shows signs of reduction in stocks as reflected by the catch trends (effort presumed nearly uniform) in 1969 (2.1 t), 1970 (1.3 t) and 1971 (2.8 t). Jhingran and Natarajan (1969) emphasised the need of stocking of catla for a better yield.

There was no decline in the stock size of mrigal during 1969-71. The stocking of this species in 1968 helped maintain the stocks in 1970 and 1971. Spawning of mrigal was poor in 1968. There were indications of poor recruitment of calbasu and intensive stocking of this species was recommended. The stocks being low, intensive stocking of this fish was recommended. The low stock size of rohu in Tilaiya was attributed to spawning failure. Stocking of fingerlings of this fish in 1968 did not improve the fishery in 1970 and 1971. It seems that rohu was unable to adjust to the ecological conditions of Tilaiya.

Guidelines for fisheries development of Konar and Tilaiya reservoir

Cyanophyceae constitute the dominant abundant part of plankton in Konar and Tilaiya and these algae also dominate the guts of catla collected from Konar. However, the levels of utilization of the blue-green algae as food is not known. The indigenous fish Thynnichthys sandhkol and the exotic silver carp are known to feed on planktonic blue-green algae, although these fishes are not favoured by consumers. The Central Inland Fisheries Research Institute has formulated a set of guidelines for the fisheries development of Konar and Tilaiya reservoirs, which are summarised below:

1. Despite the recruitment failure of Indian major carps in Konar and Tilaiya reservoirs, the spawn of some of these carps occur in the form of eggs. These may be salvaged, reared in the nursery facilities available in Bacchai fish farm attached to Tilaiya and released into the reservoir. A similar procedure can be adopted in Konar after creation of nursery facilities near the reservoir.

2. Trash and uneconomic fishes form dense populations in both Konar and Tilaiya reservoirs and some of them compete with major carps for food. Elimination of these fishes by operation of drag nets has been suggested to improve the productivity of the reservoirs.

3. Dense population of predatory fishes like W. attu, N. chitala and Barilius bola occur in Tilaiya which should be controlled for greater survival of stocked fry and fingerlings of economic fishes. Experimental fishing with gill nets showed that W. attu of the sizes that occur in Tilaiya were vulnerable to mesh bars of 45, 50, 55 and 60 mm. Similarly, 30 and 35 mm mesh bars were found very effective for Barillus bola. Long line fishing may also be attempted for the control of W. attu.

4. Charting out of the optimum concentration of fish stocks in various zones in different months has been done in Konar and Tilaiya reservoirs. Fishing should be re-orientated in the light of the above findings to improve the fish productivity and catch per unit of effort.

5. Recruitment of catla, mrigal, calbasu and rohu being poor in Konar, stocking of these fishes should be done on a continuous basis. Similar stocking is needed in Tilaiya. There are indications that rohu is unable to adjust to the ecological conditions of Tilaiya. Therefore, this fish may be excluded from stocking.

6. Size limits (Table 13.7) have been suggested for the capture of major carps in Konar and Tilaiya and suitable mesh sizes prescribed for them.

   Table 13.7. Mesh size prescribed for different species of fishes in Konar reservoir

   Fish	Prescribed mesh bar (mm)	Size (mm)
   C. catla	91	587
   C. mrigal	46	460
   L. calbasu	52	375
   L. rohita	*	450

   * Information not available (After Natarajan, 1976)

7. Flash floods and unfavourable spawning habitat on the upstream stretches of Barakar and Konar do not favour normal breeding of major carps. This renders observance of closed season redundant in the two reservoirs.

8. Selective clearance of reservoir bed by removing tree stumps and other obstructions is suggested at least upto minimum draw-down limit in Konar reservoir for facilitating better fishing operations.

13.5 MAITHON RESERVOIR

Created in the year 1957, the Maithon reservoir covers 11 490 ha. Stocking of the reservoir with the fingerlings of Indian major carps commenced in 1958 and continued in successive years. Jhingran and Natarajan (1969) observed during 1967–68 that the stocking did not have any impact on the catch even after a decade. The catch did not rise commensurate with the increase in efforts. During 1962-63 to 1967–68 the catch increased only by 4 t (9 to 13 t), despite two and half times increase in fishing effort. The reservoir has predatory catfishes Wallago attu and Aorichthys aor, which take a heavy toll of the stocked carps (Table 13.8).

13.6 PANCHET RESERVOIR

Panchet dam was commissioned in 1958. The 7 511 ha reservoir (Fig. 13.7) is rather poor in terms of total dissolved salts as reflected by the specific conductivity values of 12.33 to 19 μmhos. Dissolved oxygen is low (0.66 to 2.8 mg 1^-1) and the pH values range between 7.23 to 7.67. The reservoir was stocked only in 1958. The occurrence of catla, rohu, mrigal and L. calbasu in the fishery, without stocking indicates that the carps now reproduce in the reservoir. This was confirmed by the spawn collection survey, conducted by the Central Inland Fisheries. Research Institute during 1964, which noted the breeding of rohu and mrigal in the reservoir.

Figure 13.7. Panchet reservoir, Bihar

Fish catch structure of Panchet during 1960–61 was heavily biased in favour of major carps, mrigal and rohu. In 1967–68, mrigal was the dominant species and catla the second, closely followed by rohu. By 1967–68, the catfishes (Aorichthys aor, Wallago attu and others) formed the major component of the fish harvest (Table 13.9).

A relatively recent report on Panchet reservoir depicts deterioration in the environment due to pollution (Mukherjee et al., 1986). Apart from a heavy sediment input of 0.67 ha m m^-2 yr^-1, arising from the denuded catchment area of 6 120 km², the reservoir receives effluents from 31 different industrial establishments. The 21 coal industries alone add 0.9 million t of effluents per minute. bearing 4% fly ash. Four thermal power plants add huge quantities of effluents with pH above 10 and total solids above 5 000 mg 1^-1. All the effluents, which include heavy metals, phenol and cyanide, exert stress on the ecosystem.

13.7 BADUA RESERVOIR

Badua reservoir (86° 30' E and 25° 30' N), 80 km south of Bhagalpur was commissioned in 1963. The dam comprises an earthen dyke storing 128.29 million m³ of water for irrigation purposes. The reservoir has a surface area of 880 ha, the maximum and mean depths being 32.0 m and 14.57 m respectively. The drainage covers 297 km², receiving rainfall of 163 to 468 mm during July-October. The discharge from outlets is estimated at 1 000 m³ second^-1, feeding the right and left canals irrigating 425 km² of agricultural land.

Verma and Munshi (1983), described Badua reservoir as monomictic, having thermal stratification during summer and isothermal conditions during monsoon and winter months. Alkaline in reaction (7.5 to 8.1), the water is saturated with oxygen (80–l00%) throughout the year. Oxygen depletion in the bottom layer is reported (5.6 to 6.9 ml 1^-1), accompanied by accumulation of nutrients (silicate, phosphate, and nitrate) in the deeper layers of water.

The maximum rate of primary productivity is at 0.5 m depth @ 98 mg C m^-3 hr^-1 (gross) and 70 mg C m^-3 hr^-1 (net). Phytoplankton constitute 65 to 67% of the plankton community with Cyanophyceae and Bacillariophyceae as the dominant groups. Cymbella turgeda, Synedra ulna, Gomphonema sphaerophorum, G. lanceolatum, and Navicula cuspidata are the common diatoms recorded from the reservoir, while Microcystis aeruginosa constitute the bulk of the Cyanophyceae. Other blue-greens are Merismopedia glauca, Anabaena unispora and Gloeocapsa punctata. Members of Chlorophyceae present are Chlorococcum sp., Closterium setaeum, Cosmarium puntulatum Bulbochaete obliqua and Oedogonium oviforme.

The State Fisheries Department has been stocking the reservoir with fingerlings of Catla catla, Labeo rohita and Cirrhinus mrigala in the ratio 4:3:3, since 1975. An estimated 1 128 500 fingerlings were stocked until 1979. Total fish landings during 1975–76, 1976–77, 1977–78 and 1978–79 were estimated at 4.03,3.90, 4.70, and 5.88 t respectively.

13.8 NALKARI RESERVOIR

Nalkari is a tributary of the river Damodar, which is dammed to create the 991 ha reservoir. The lake was filled in the year 1967 to meet the water requirements of Patratu thermal power station and the associated township. Sarkar (1982) described the soil and water quality of the reservoir. The soil is acidic (5.4 to 6.2) with texture varying from sandy loam to sandy clay loam. Calcium carbonate content of soil varies from 0.5 to 1.0% and the organic carbon is in the range of 0.26 to 0.67%. Available nitrogen (47 to 150 mg 100 g^-1) shows medium to high productivity while phosphorus is in high productivity range (10 to 16 mg P²O⁵ 100 g^-1).

During the summer stratification, there is a fall of 9 °C in temperature in the hypolimnion, which is accompanied by a strong chemical stratification. Oxygen decreases from 7.6 mg 1^-1 at the top to 0.9 mg 1^-1 at 14 m depth. The tropholytic layer is characterised by accumulation of free carbon dioxide and bicarbonates, absence of carbonates and low pH. The surface water is above neutral in pH (7.8 to 8.3) and the total alkalinity ranges from 48 to 55 mg 1^-1. The water is medium hard. Among nutrients, nitrate and phosphate are poor, while the silicate is moderately rich.

13.9 STATUS OF RESERVOIR FISHERIES IN BIHAR

Bihar is the second largest inland fish producing State in India, contributing 11% (0.185 million t) to the national production of of 1.7 million t (1991–92). The track record of the State in the aquaculture sector is impressive. Bihar's total nursery area of 350 ha is the largest in India and its annual fish seed production of 348 million fry is the third highest. However, the large water bodies do not get similar attention and consequently they do not contribute to the inland fish production to the extent they could. The per capita fish consumption in the State ranging from 0.08 to 0.13 kg is one of the lowest in India, thereby calling for an improvement in fish production.

Although Bihar is endowed with rich and diverse water resources in the form rivers, floodplain lakes, wetlands and man-made lakes, no serious developmental efforts have been directed towards increasing fish production from these large water bodies. Fisheries development from the open waters is considered to be environment-friendly and labour-productive. Considering that Bihar is also plagued with a very low per capita income and protein intake, fishery development in open waters assumes greater significance in the State, from social and economic perspectives. Reservoirs that spread over an area of nearly 100 000 ha can play a pivotal role in increasing the fish availability in the State and providing gainful employment to its rural poor. However, the State has a long way to go towards optimum utilisation of this important resource.

Factors that hamper the growth of reservoir sector are many. One of the main constraints that inhibits the development process is the infirm database, both on resources as well as the production processes. Documentation on reservoir fisheries resources in the State is grossly inadequate and even a reliable estimate of the total area under different categories of reservoirs is not available. The State Fisheries Department neither have the jurisdiction nor the mandate to initiate fisheries development in all the man-made lakes. Out of more than 125 reservoirs in the State, covering an area of 96 695 ha, only 14 with a total waterspread of 9 845 ha are under the control of Fisheries Department, resulting in insufficient information on their production dynamics. This serious lacuna has affected the development process. In the absence of a meaningful R&D back-up, almost all the reservoirs in the State are managed on ad-hoc basis, leading to poor realisation of their fish production potential.

Information on fisheries management and fish yields from the reservoirs of Bihar is equally scanty. Ahmed and Singh (1992) estimated the yield from reservoirs under the Department of Fisheries at 5 kg ha^-1, based on the fish production of 13 small and one medium reservoirs. As per a recent communication from the State Department of Fisheries, 24 small reservoirs in the size range from 21 to 469 ha, with a yield of 3.91 kg ha^-1, calculated on the basis of their mean area. If the area at FRL is considered, the yield rate will drop further. Similarly, three medium reservoirs in the size range 1 050 ha to 1 400 ha (at average level), covering a total area of 3 785 ha produce just 7 158 kg of fish (1.89 kg ha^-1). Under the large category, the 7 500 ha Kansjor reservoir produces 800 kg of fish with a yield of 0.107 kg ha^-1.

The production level and stocking rate for 37 reservoirs are available (Table 13.10). Covering an area ( based on mean reservoir level) of 55 163 ha, they produce 29 942 kg i.e., 0.54 kg ha^-1 of fish. The fish yield would be much lower, if calculated on area at FRL. Thus, the reservoirs of Bihar have one of the lowest fish yields in the country.

Misc. = Miscellaneous
^*Source: State Dept. of fisheries

In the absence of data, it is difficult to estimate the fish production of the reservoirs. If the available literature on the environmental parameters and production dynamics from a few reservoirs is any guide, the water tends to be rich in terms of the ionic concentration and nutrients, mainly by virtue of rich drainage in case of the South Bihar reservoirs and due to the intrinsic productivity of the basin soil in the alluvial plains of the North. The abundance of fish is high. However, the conducive environment and the high primary and secondary productivity are not reflected in a correspondingly high fish yield. The very low fish yields reported from 6 districts of Bihar, ranging between 0.8 and 7.5 kg ha^-1 (Table 13.11), are the poorest in India.