5. ANDHRA PRADESH

Andhra Pradesh is the fifth largest State in India, both demographically as well as geographically. The State consists of the eastern coastal belt, the Telengana area of the north and the Rayalseema area of the Southwest. The northern part of Telengana is mountainous receiving an annual rainfall of the order of 102 cm. In the south, the terrain is undulating with isolated hills and an average precipitation of only 50 cm a year. The State is a hot, semi-arid dryland, except the coastal districts which are very fertile and have a highly productive agriculture.

Andhra Pradesh is drained, by three large rivers (catchment< 20 000 km²), including the Godavari and Krishna, which have an annual discharge of 105 000 and 67 675 million m³ respectively. Pennar, the third major river carries 3 238 million m³ annually. The medium rivers (catchment 2001 – 20 000 km²) comprising nagavali, Sarda, Eluru, Gumdlakamma,Musi,Paleru,Muneru and Kunleru have an annual discharge of 6 430 million m³. More than 33 minor rivers (catchment > 2000 Km²) of the State are small coastal streams flowing into the Bay of Bengal, carrying a total of 6 764 million m³ of water. All the rivers in the State are east-flowing and are harnessed for irrigation and power generation.

People living in the dry regions of Telengana and Rayalseema realised the need for irrigation from time immemorial and learned to create reservoirs on small streams, rivulets and creeks to store water for irrigation. Like their counterparts in Karnataka and Tamil Nadu, these improvised irrigation reservoirs, locally called tanks are often overlooked while compiling the reservoir resources data.

5.1 RESERVOIR FISHERIES RESOURCES

Andhra Pradesh has a long tradition of constructing big dams and reservoirs. Some of the oldest man-made lakes in the country are situated in the State. Hussainsagar in the heart of Hyderabad city is 500 years old, followed by Saroornagar and Mir Alam, which had been in existence for the last 275 and 170 years respectively. Banjara, Osmansagar and Himayatsagar are the other old reservoirs, created between 50 to 65 years ago. Srivastava et al. (1985) have listed 117 reservoirs, along with their areas at FRL and the fish production rate. However, a recent communication from the State Fisheries Department mentions only 102 reservoirs. After reconciling the discrepancies by verification with other sources such as maps and other documents, a list of 137 reservoirs has been prepared (Table 5.1 : Fig. 5.1). More than 46 reservoirs in Andhra Pradesh are said to be under dispute, where no fishery activities exists and Sreenivasan (1993) reports that hardly a dozen man made lakes in the State have been developed for fisheries.

Andhra Pradesh has 98 small reservoirs, 2 800 tanks, 32 medium reservoir and 7 large reservoirs with a total surface water area of 458 507 ha (Table 5.2). Vishakhapatnam district has the maximum number of reservoirs (20), followed by Rangareddy, Prakasam, Nellore and Karimnagar districts with 10 reservoirs each. While Vizianagaram and the two Godavari (east and west) districts have only small reservoirs, Ranga Reddy, Nellore, Nalgonda, Karimnagar and Chitoor have large concentration of small reservoirs. Medium reservoirs are well-dispersed among the districts and the seven large reservoirs are distributed among Guntur, Karimnagar, Kurnool, Nellore and Nizamabad districts (Table 5.3). Majority of the reservoirs in the State are small (98), followed by those in the medium (32) and large (7) categories. The seven large reserviors have a total surface area of 190 151 ha, while the medium and small reserviors cover 66 429 ha and 24 178 ha respectively. Taking the irrigation tanks into the account the total number and area is much higher.

N.A.= Not avaiable

Figure 5.1. Distribution of reservoirs in Andhra Pradesh

Irrigation tanks of Andhra Pradesh are classified into two categories, viz., perennial and long seasonal (Anon., 1994a). Although an inventory of all perennial tanks in the State is not available, their number and area by districts are known. All the perennial tanks, except those of Srikakulam. East Godavary and Krishna districts(which have an average size less than 10 ha), have been considered as man-made lakes. More than half of the perennial tanks are situated in East Godavari district, both numerically and in terms of waterspread. The 2 800 perennial tanks cover a total area of 177 749 ha in 18 districts.

Reservoirs and tanks together constitute 458 507 ha of water area in Andhra Pradesh, (Table 5.4) which is the second largest in India.

Considering the size of the resource and its potential for fisheries of the State, scientific attention received by the reservoirs of Andhra Pradesh is inadequate. A systematic study was done only in Nagarjunasagar as part of the All India Coordinated Project on Reservoir Fisheries from 1971 to 1981. Hussainsagar in Hyderabad, the oldest reservoir in the country, has attracted attention mainly on account of pollution. A cursory appraisal of eight man-made impoundments in the vicinity of Hyderabad city was done by Zafar (1986).

5.2 NAGARJUNASAGAR (Fig. 5.2)

Nagarjunasagar reservoir is situated on the main river Krishna within the geographical coordinates, 16°34' N and 79°19' E. The 28 475 ha reservoir extends to Nalgonda and Guntur districts, which are divided by the Krishna. Predominantly an irrigation reservoir serving 1.37 million ha of paddy land, the reservoir also generates 905 MW of hydro-electric power. Being on the mainstream, the reservoir has a vast catchment area of 215 194 km². Most of the drainage originates from the Western Ghats, receiving an annual precipitation of 90 cm from the southwest monsoon.

The reservoir, at FRL, holds an enormous 11 560 million m³ water and shrinks to 1 410 million m³ at dead storage level, resulting in a water level fluctuation of 58 m. The mean depth at the average level is 29.9 m. Shoreline of Nagarjunasagar is very irregular with a shoreline development index of 7.89. Inflowing water readily gets mixed with the whole column. The high flushing rate (3.0 to 6.2) point to the possibility of nutrient loss. Even during the months of summer stagnation, the deeper outlets drain away nutrients. Nevertheless, the productivity remains high due to the input of nutrients through the inflow and the conducive environment of the bays.

Prevailing climatic conditions play a key role in the production of the reservoir. Nagarjunasagar is situated in one of the warmest regions of India, the summer air temperature often touching 45°C. With no winter season, minimum temperature never drops below 16°C, thus preventing the formation of any thermal stratification in water, while the warm bottom accelerates bacterial decomposition. The wind induced turbulance churns the water to facilitate nutrient mixing.

The high productivity of the reservoir is manifested through many physico-chemical attributes of water. It is a typical hard water lake with a high nutrient and mineral content. The hardness as CaCO₃ varies between 50 to 200 mg l^-1 and the pH between 7.6 to 8.6. The inundated area is rich in limestone and the free CO₂ present in the inflowing water causes dissolution of CO₃ into bicarbonates. Thus, the water retains a very high ionic concentration in terms of total alkalinity and specific conductivity. Carbondioxide is present in the surface, in free state, only during the flood season. During the other seasons, it is used up at a faster rate than the supply. Carbondioxide for photosynthesis is derived from bicarbonates. Though the nutrient build-up in terms of phosphates is not high, the levels of nitrate and silicate are high (Pathak, 1979).

There is a sharp discontinuity between the oxygen-rich trophogenic layer and the oxygen-deficient tropholytic zone at the bottom during summer, accompanied by the decrease in pH and increase in specific conductivity and total alkalinity towards the bottom.

The productivity manifests itself by a flourishing plankton community. The annual water renewal plays an important role in its seasonal succession. The massive annual floods bring, in minerals and nutrients, but they also dislodge and sweep away the plankton. As soon as the destabilising effects of the flood discharges are over, the plankton community recovers. The phytoplankton cycle more or less conforms to a general pattern of aestival (summer) and autumnal (post-monsoon) seres, punctuated by the hiemal (monsoon) minima(Sugunan, 1980). The protected bays which are shallow, undisturbed and nutrient-rich bear blooms of Microcystis aeruginosa. The deep lentic sector has diatom blooms in summer and winter. Sectoral variations in the composition and diversity of plankton are clearly discernible. The fluviatile lotic sector retains a rich variety of algae, dominated by Chlorophyceae, blue-greens and diatoms. The lentic waters, especially the bays, have blue-green algae in blooms and a very low species diversity index (Sugunan, 1991). Though the stress factors are responsible for keeping the diversity index low, they do not lower the productivity in the main sectors of the reservoir, as stability is more directly related to diversity than does the productivity.

Figure 5.2 Nagarjunasagar reservoir, Andhra Pradesh

Barring the rich populations of molluses in the bays, the benthic invertebrate fauna in the reservoir is rather poor due to the predominantly rocky nature of the substratum and the frequent and abrupt level fluctuations which prevent the effective colonisation of the available substrata (Sugunan and Das, 1983). That the vicissitudes of level fluctuations retard the growth of periphyton on natural substrate has been corroborated by the rapid and dense deposition of these organism on artificial substrata (Sugunan and Pathak, 1986). Steadily charged with nutrients and salts from the allochthonous sources, the well-mixed and well-illuminated reservoir has all the prerequisites for natural eutrophication, despite its deep basin. The rate of primary production is very high, up to 590 mg C m^-2 day ^-1 during the summer. The energy fixed by the producers range from 19 577 × 10³ to 24 674 × 10³ k cal ha^-1 yr^-1 (as oxygen), which is 0.33% of the light energy. In term of carbohydrates, the conversion is 0.34%.

David et al. (1969b) described 38 species of fish from the reservoir to which Bhatnagar and Sugunan (1978) added another 31. There are more than 20 species of carp minnows, 25 small catfishes and other uneconomic species which compete with the commercial species resulting in low yield of commercially important fish.

The commercial catch comprises Labeo fimbriatus, L. calbasu, Tor khudree, Catla catla, Cirrhinus mrigala, L. rohita, Pangasius pangasius, Aorichthys aor, A. seenghala, Silonia childreni, and Wallago attu. Among them L. fimbriatus and L. calbasu formed the indigenous carps, which together contributed more than 40% of the catch in the initial years. Later, their percentage declined to 13% in 1975–76. During 1979–80, the two species together formed 16% of the catch (Table 5.5).

Food habits of most of the fishes are known. L. fimbriatus and L. calbasu feed mainly on detritus (Anon., 1982; Vinci and Sugunan, 1981), while A. aor (Ramakrishniah, 1984) A. seenghala, Silonia childreni (Vinci, 1986 and 1984) and W. attu (Anon., 1982) feed on carp minnows and other small fishes. Pangasius pangasius lives almost exclusively on molluscs. Even among the less important and the weed fishes, plankton does not figure as a major item of food except for Ambassis spp. and Rohtee sp. (Table 5.6 to 5.8).

Organic detritus forms the major food of Rhinomugil corsula and Osteobrama vigorsii (86% and 60% of the gut contents respectively), the other food items of the mullet being diatoms, blue-green algae, green algae, zooplankton and benthic fauna. O. vigorsii consumes insects, diatoms and molluscs, in addition to organic detritus. Pseudeutropius taakree is the only fish having insects as the predominant food (74.2%), the other components of the stomach contents being fish (14.8%), prawn, organic detritus (30%) and plankton. Channa marulius is essentially a predatory fish living on trash fishes (76.50%), prawn and insect.

Salmostoma phulo phulo which form 86.45% of the trash fishes is detritophagus; the detritus forming 80% of its gut contents, followed by fish remains (10.75%), crustaceans (5.12%), insect parts (3.13%), Chlorophyceae (0.50%), diatoms (0.25%) and Cyanophyceae (0.25%). Barbus sp., Barilus spp., Chela atpar, Dania aequipinnatus, Osteobrama cotio, Oryzias melastigmus and Puntius sophore also had their stomach contents dominated by organic detritus. Ambassis spp., and Rohtee ogilbii lived mainly on zooplankton. Gagata itchkeea and Glossogobius giuris were predatory on other fishes.

*Fishing effort was low due to civil strife in the State

The reservoir has a rich plankton community, comprising Cyanophyceae, (mainly Microcystis aeruginosa), Bacillariophycea and Chlorophyceae, apart from a dense population of zooplankton, dominated by copepods and rotifers. The plankton production in Nagarjunasagar is one of the richest, among Indian reservoirs. A perusal of Tables 5.6, 5.7 and 5.8 clearly shows that the plankton is hardly utilized as a major food ingredient by any of the commercial fishes of the reservoir.

M. aeruginosa, Merismopedia sp. and Oscillatoria sp., which are the mainstay in the plankton community, occur in the stomachs of Labeo calbasu, L. fimbriatus, L. rohita, Rhinomugil corsula in very low percentages (never exceeding 0.59% of food, by volume). They were not traced in the stomach contents of trash fishes either.

Among Chlorophyceae, Pediastrum sp. and Spirogyra sp. form 5% of stomach contents in L. calbasu. Green algae contribute insignificantly to the food of L. fimbriatus (5.5%) and Cirrhinus mrigala (0.5%). Among trash fishes, Barilius spp. have 20% of their gut contents contributed by Chlorophyceae. Spirogyra sp., Pediastrum spp. and Cosmarium sp. are reported from the gut contents of Chela atpar, Glossogobius giuris and Salmostoma phulo phulo.

(Anon. 1982)

Plankton and benthos as fish food organisms

Share of diatoms in the gut contents of fishes is better, compared to green and blue-green algae, though it could not be established whether the diatom shells encountered in the stomach were engulfed from the plankton phase or devoured along with organic detritus. Fragilaria, Cymbella, Amphora, Asterionella, Navicula, Tabellaria and Frustulia form 10.57% of stomach contents in L. calbasu. Diatoms form 25% of the gut contents of L. fimbriatus, 2.5% in C. mrigala, 1.66% in L. rohita, 10.16% in Rh. corsula and 5% in P. kolus. Among trash fishes, P. sophore consumes Fragilaria, Navicula, Amphora, Synedra and Melosira (22.52%) while Oryzias melastigmus feeds on Navicula, Synedra and Cymbella.

Among zooplankton, copepods like, Cyclops, Diaptomus sp. and nauplii were very rare in the stomachs of commercial fishes. They form 0.98% in L. calbasu along with rotifers and 2% in P. kolus. Copepods form the major food of Ambassis baculis (70%) and A. nama (65%). Rotifers and cladocerans are hardly consumed either by commercial or trash fishes excepting Rohtee ogilbii (62%). Gastropods are largely consumed by Pangasius pangasius almost as a sole food item. Molluscs are taken by P. dobsoni (60%), P. kolus (60%), T. khudree (22.8%) and Osteobrama vigorsii (20%). But considering the size of their populations, the latter species does not possibly make any impact on the benthic community by way of niche utilization.

Niche utilization

Plankton as niche remains largely unutilised. The carps viz., L. fimbriatus and L. calbasu, which together constitute 16.2% of the catch live mainly on detritus. Catfishes other than Pangasius pangasius are predatory on carp minnows and other trash fishes. This group comprising Aorichthys aor, A. seenghala, Silonia childreni, Wallago attu, Bagarius bagarius, etc., are living on a long food chain and hence considered uneconomic species, P. pangasius, on the other hand, feeds on molluscs and not considered to be on a long food chain. It is compatible with carps and utilizes a major niche namely bottom macrofauna (molluscs being the most dominant component of bottom fauna).

L. calbasu, L. fimbriatus and P. pangasius account for more than 50% of the total fish produced in the reservoir. While all the above mentioned fishes depend on detritus for food, either directly or indirectly, none of them feeds on plankton. The rich plankton crop of the reservoir remains more or less unutilised and enriches the bottom detritus on death and sinking. In all probability, the diatom shells encountered in the guts of fishes are a part of detritus. Thus, there are three basic routes of energy transformation. L. fimbriatus, L. calbasu and C. mrigala (20.38%) have the shortest food (detritus) chain followed by that of P. pangasius (27–37%) which is on a detritus-molluscs chain. The forage feeders (40%) such as A. aor. A. seenghala, Si. childreni and W. attu are on a long chain i.e., either a primary energy - herbivore - predator(grazing) chain or primary energy -dead organic matter - detritivores-predators (detritus chain), both involving considerable dissipation of energy at each trophic level (Natarajan and Pathak, 1983).

Fish production potential

Natarajan et al. (1979) estimated that the reservoir can produce 3408 t of fish at secondary consumer level. Thus, the actual catch falls short by more than 3 200 t. The shortfall seems to be due to the imbalance in the species spectrum. Nagarjunasagar is an example of a situation where management missed the opportunity of stocking desirable fish species at the time of trophic burst. The initial bloom of plankton remained unutilised as direct food and contributed to the energy at detritus phase. Though the indigenous detritiphagous fish such as L. fimbriatus and L. calbasu could take advantage, they suffered setback due to pressure from predators. The non-predatory P. pangasius seems to have found a favourable breeding and feeding environment. Table 5.9 shows the change in favour of catfishes over the years. The poor performance of detritiphagous carps and large proportion of non-Pangasiuscatfishes in the catch are a cause of concern.

Stocking

Stocking has been erratic, both in qualitative and quantitative terms (Table 5.10), the total number stocked in a year ranging from nil to 833 700 during the period from 1964 to 1978–79. Species composition of the stock was also inconsistent. The stocking density was only 0.8 ha^-1 yr^-1 up to 1969, but increased to 3.49 ha^-1 yr^-1 during the four years from 1970. Although it reached 19.2 ha^-1 in 1978, it made no difference in the fish catch composition, which continued to be dominated by catfishes (Table 5.9). Considering the vacant niche of zooplankton feeder in the reservoir, and annual stocking of 1.8 million fingerlings of catla catla was suggested by the All India Coordinated Project on Reservoir Fisheries (Anon., 1977). L. calbasu (600 000). C. mrigala and Cyprinus carpio (500 000 each) were also recommended for better utilisation of detritus. This required a stocking rate of 3.4 million yr^-1, but only 64 000 to 353 000 fingerlings could be stocked per annum (Table 5.11).

* Total includes 50 000 in 1975–76, 100 000 in 1976–77 and 116 000 in 1977–78 of M. malcolmsonii

Other constraints

Apart from the undesirable species-mix and understocking, there are other logistic problems coming in the way of yield optimisation. The reservoir lies in a reserve forest area with very little inhabitation along its margin. All the productive areas, lying in remote places not connected by road, remain unexploited, since there is no means to market the fish without spoilage. The craft used are obsolete and tedious to operate. A state-run motor boat ensuring quick transport of fish would be an incentive for fishermen to fish untried fishing grounds of intermediate and bay sectors, which are known to be very productive. The present free for all licensing system is not conducive to development. There is no check on the number of units operated or their quality and dimensions. Neither is the catch monitored regularly by the authorities. Indiscriminate capture of desirable species at the breeding grounds of Peddamunigala bay continue unchecked and this single factor may be chiefly responsible for the decline of indigenous carps. Although there is a closed season, it is not enforced. The fishermen live in abject poverty and are exploited by private money lenders, who pay them a very low price for their catch. Formation of efficient cooperatives, provision of credit to the fishermen, and assistance in marketing their catch are options which should be seriously considered as a way to improve the socio-economicconditions of the fisherfolk.

5.3 HUSSAINSAGAR

Hussainsagar reservoir was constructed in 1562 in the city of Hyderabad. Because of its age and the anthropogenic environmental stress it is subjected to. Hussainsagar is in an advanced stage of eutrophication. On account of its proximity to centres of learning, it attracted the attention of many scientific workers. Srinivasan et al. (1965) and Zafar (1966) made the first comprehensive ecological investigations in Hussainsagar. At full level, it covers 4016 ha, which shrinks to 1 942 ha by the end of the dry season. The `V' shaped basin holds 9.25 million m³ of water and has a very irregular shoreline. Hussainsagar receives water from three channels, viz., Kukatpally nala, Bownpalli nala and Balkur channel (Fig. 5.3). The outlets comprise the flood gates in the centre of the dam and the sluice gates on either side. Floodgates are opened only during the flood season.

The twin cities of Hyderabad and Secunderabad are 2 040.6 km² in area with a population of 1.8 million. Average rainfall in the city is 76 cm, mostly from the southwest monsoon. Catchment of the lake, which includes the stormwater from the city as cover 241 km².

Hussainsagar is one of the highly polluted reservoirs in India. Kukatpally nala, the main feeding channel of the reservoir, is flanked by 261 major and minor industries discharging untreated or inadequately treated effluents. Bownpalli and Balkur channels are comparatively small and discharge mainly the stormwater combined with domestic and city wastes. The pollutants include strong acids, alkalis, burnt diesel and heavy oils, pesticides, asbestos, cement and biochemical wastes (Hingorani et al., 1977). Although there is no direct sewage discharge into the lake, the city sewage channel, known as K. - main, which runs parallel to Kukatpalli nala has developed leaks and sewage gets mixed with the nala water, finding its way into the reservoir (Hingorani, 1980).

The nitrogen and phosphorus loading in the reservoir is considerable. The maximum level of inorganic nitrogen was 3.2 mg 1^-1 and that of PO₄- P 0.43 mg 1^-1 (Zafar, 1986). The pollutional effects, become acute during the summer. The pH (which is normally around 8), falls rapidly to 7 with a heavy build up of CO₂ to the level of 95 mg 1^-1 (Ghosh and George, 1989). The bicarbonate alkalinity of 92 to 385 mg 1^-1, high chlorides, little or very low level of dissolved oxygen and accumulation of H₂S and heavy metals are the other impacts of pollution.

Figure 5.3. Hussainsagar reservoir, Andhra Pradesh

The effluent discharge point near Indian Drugs and Pharmaceuticals Limited (IDPL) at Kukatpally nala has dissolved free CO₂ up to 200 mg l^-1 and total alkalinity of 280 to 560 mg l^-1. The effluent has a pH of 6.1, suspended solids 4 540 mg l^-1. Bod level of 4 080 mg l^-1, and COD 10 470 mg l^-1. Rao (1990), after comparing the CO₂, dissolved oxygen alkalinity, chloride content and the nutrient flux during the mid '60s and late '80s, concluded that the pollution of the reservoir has considerably increased.

Bioaccumulation of chromium, manganese and mercury is in excess of the permissible limits in water and sediment phase (Seenaya and Prahalad, 1987 and Prahalad and Seenaya, 1988; Table 5.12).

ww= wet weight,
dw=dry wt. After Prasad, 1993

Frequent fish mortality due to pollution has been reported from the reservoir, the most vulnerable sites being Nallagadda, Patigadda, Railway bridge, and Road bridge near IDPL. The fishes affected are mainly Etroplus suratensis, Ompok pabda, Puntius spp., and Mystus spp. The cause of death is attributed to asphyxiation (Hingorani, 1977).

Since the mid 1970s floating weeds, especially the water hyacinth, choke the lake, covering one third to half of the surface. The problem is acute during the summer, when the floating plants attain a height of 1 m. Municipal authorities incur enormous expenditure in cleaning the weeds manually. But the plants soon grow back to their original density. Clear portions of the lake have thick blooms of Microcystis aeruginosa and other blue-green algae. Ghosh and George (1989) report a poor species diversity in terms of phyto and zooplankton.

The fish fauna comprises Wallago attu, Channa marulius, Mystus spp., Chela sp., Ompok sp., Heteropneustes fossils, Puntius spp., Etroplus spp., and Labeo spp. The transplanted carps, L. rohita, Cirrhinus mrigala and Cyprinus carpio appear in the catches very rarely. In the absence of any regular stocking, the wild populations are being exploited by the fishermen. A change in population structure of fishes has been reported due to rapid eutrophication, carp species giving way to air-breathing fishes and catfishes.

Twelve common species of fish including Mastacembelus spp., Chela clupeoides, Rasbora buchanani, Puntius kolus, Brachydango reria, Labeo calbasu, L. fimbriatus, Danio aequipinnatus, earlier reported by Rahimullah (1943) are now found only in low numbers. But hardy species like Heteropneustes fossilis, Clarias batrachus, Mystus bleekeri, Garra mullya, Gambusia affinis, Poecilia reticulata and Notopterus notopterus have become common (Rao, 1990). There is no system to collect the catch statistics or to monitor the fishing effort. An estimated 10 to 18 t of fish catch was reported in 1975–76

There are no fishermen regularly operating in this reservoir and the fishing is carried out by part-time fishermen who employ gill nets, cast nets and rod and line for raising extra income. A gill net measures 10 × 2 m with a mesh size varying from 10 to 30 mm. On account of the unremunerativeness of fishing operations, fishermen cannot afford to own a boat. They depend on improvised crafts such as floats, inflated tyres and rafts for laying and lifting of nets.

Ecosystem recovery is an uphill task. Problems posed by the man-induced eutrophication, and industrial pollution are enormous. Pollution abatement can be achieved only by:

1. diverting the city sewage to treatment plants without polluting the channels,

2. effective treatment of industrial effluents, and

3. control of macrophytes

Thereafter, the problems arising from the pollution coming from the adjoining slums will have to be addressed on a social plane. In the present situation, not only the environment is unhealthy for fish populations, but the existing fishes are a potential health hazard, in view of bioaccumulation of heavy metals and chemicals.

5.4 YERRAKALAVA RESERVOIR

Yerrakalava, an important rivulet originating from the Eastern Ghats of Khammam district, joins Upputeru, the outlet channel of the Kolleru lake. Yerrakalava is dammed 54 km away from Eluru, creating a waterspread of 1 550 ha at FRL of 81.05 m above MSL. Situated between the geographical ordinates 81° 15' 22" and 17° 5' 44' N, the dam was originally conceived to provide relief to 8 100 ha of downstream land from flood. However, subsequently, the water from the reservoir was also diverted to irrigate 10 000 ha of agricultural land. The Yerrakalava reservoir also improves water circulation in the Kolleru wetlands. The reservoir has a catchment of 1 073 km² and holds 125.3 million m³ water at FRL. The mean depth at FRL is 8 m.

Limnological studies were conducted in the reservoir during October-December 1993. The reservoir is productive, with high values of total alkalinity (90 to 110 mg l^-1) and total hardness (80 to 100 mg l^-1). The water is warm (22.0 to 32.5 °C) and clear (transparency 43 to 178 cm), with a pH range of 7.4 to 8.4. Dissolved oxygen at the surface ranges from 2.0 to 8.8 mg l^-1 and the carbon dioxide, when present, 4 to 6 mg l^-1. The rate of carbon fixation was high with values recorded at the surface and in sub-surface ranging between 41.66 mg C m^-3 hr^-1 and 104.16 mg C m^-3 hr^-1 as observed in the months October to December, 1993 (Table 5.13).

The flushing rate of Yerrakalava is very low, which causes the growth of a variety of submerged vegetation. Hydrillaand Chara dominate the margin, while the deeper zones have patches of Vallisneria. Mats of Spirogyra are also reported from some places.

(CICFRI Barrackpore)

The untreated effluents from Adivasi Paper Mill, located at Aswaopeta in Khammam district find their way into this reservoir through Jalleru, a rivulet tributary to Yerrakalava. Downstream, the river Yerrakalava receives waste discharge from a distillery and a paper mill. This harms the recruitment of fish in the estuarine zone.

There are about 175 active fishermen residing in 6 villages contiguous to the reservoir, who make a living out of fishing (Table 5.14). All the 175 permanently settled active fishermen exploit the fish of the reservoir throughout the year and there is no restriction on their fishing operations. They are free to operate their gear anywhere in the reservoir. In addition to them, about 25 fishermen of A. Polavaram, a distant village, also exploit the fishery wealth of the reservoir during seasons of god catch. About 200 fishermen migrate to Yerrakalava reservoir area in February-June. They come from villages around Kolleru lake and return with the commencement of monsoon.

Fishing operations on Yerrakalava reservoir mainly use set gill nets, cast nets, long lines and basket traps. Since the reservoir is not cleared of tree stumps, other types of nets cannot be operated. Set gill nets and cast nets are employed for capturing carps and catfishes, while pandiri mavulu, the basket traps are used for prawns and murrels. Among the traps, gari is utilised for eels, and sanna mavulu are used for minor carps, perches, spiny eels and barbels.

Fishermen who are permanently settled and conduct fishing year round in the reservoir, usually possess the following gear for use in different seasons and for catching different species.

(CICFRI Barrackpore)

c. Traps

1. Pandiri mavu - 100 to 150, usually in three sizes (big, medium and small), rectangular shape.

2. Sanna mavu - 50 to 100, with or withoutflaps (gandava mavu), rectangular in shape.

3. Gari - The cone shaped traps numbering 10–25, the location of traps set are indicated with the help of a float.

d. Long lines - Usually 2, each with 50 hooks.

e. Utchulu - About 50 scare traps

Gill nets are usually set for about 14 hours. The fish catch from these units ranges between nil to 9.75 kg and the catch per man hour 0.29 kg. The cast net is operated for 6 hours with a yield of one kg of Macrobrachium malcolmsonii and the catch per man hour is 0.16 kg.

Almost all of the active fishermen possess a flat-bottom dug out canoe made of teak. Others employ a round bottom dug out canoe made from palm trees.

Ichthyofauna

Thirteen species of fish have been recorded from the reservoir, as well as a freshwater prawn, Macrobrachium malcolmsonii (Table 5.15).

Catla, rohu, mrigal and Wallgo attu are caught during monsoon months in substantial quantities. Their size ranges from 3 to 6 kg. The summer fishery is dominated by minor carps, prawns and murrels. Middlemen purchase the fish from the fishermen. There is no sale of fish by the fishermen directly to consumers. Demand for fish is high on Thursday, the weekly market day at Jangareddygudem, the nearby town.

5.5 RESERVOIR FISHERIES IN ANDHRA PRADESH

Fish production in the man - made lakes of Andhra Pradesh shows a great variety. Reservoirs of the Nellore district are particularly productive, the yield rate ranging from 93 to 142 kg ha^-1 among the medium category, and 643 to 1 273 kg ha^-1 among the small ones. All types of reservoirs yield less fish in Karimnagar, Hyderabad, Kurnool, Medak and Warrangal districts (Table 5.1). Production figures are available for 38 small, 28 medium and three large reservoirs (Srivastava et al., 1985; Table 5.16).

Very little information is available on the reservoir fisheries of Andhra Pradesh. Production figures, stocking details, craft, gear and manpower deployed in respect of individual reservoirs are not kept by any agency, mainly due to the free fishing systen followed in the State.

Two types of fishing practices are followed in the State i.e., free fishing and auctioning. The large water bodies are managed on the basis of common property norms where fishermen are free to fish after obtaining a license from the local Assistant Director of Fisheries, issued free of cost. The number of units or quantum of fishing effort to be employed by a licencee is restricted. However, the local authorities are not provided with sufficient manpower, resources or executive power to enforce such restrictions. Similarly, the rules regarding closed season meant for conserving and protecting the broodstock are not strictly enforced. Free fishing is not conducive to the development of reservoir fisheries. Licence fee or royalty of some sort need to be levied from the fishermen to infuse a sense of accountability and to provide the State with the much- needed resources to provide pre- and post-harvest infrastructure facilities for the fishermen. In many reservoirs, the fishermen do not operate their gear in remote places due to lack of quick transport of their catch. State's intervention is necessary for providing facilities for transport of catch and marketing channels.

(Srivastava et al., 1985)

Stocking in reservoirs is done arbitrarily without any considerations on stocking density or species-mix. Largely it is determined by the seed availability.

Fishing rights in the small reservoirs in the State designated as tanks are auctioned off to private contractors, usually for a period of 12 months. The contractor hires fishermen for netting, on a daily wage or royalty basis. This short-term lease is not in conformity with norms of conservation and development since the contractors capture the entire stock, leaving nothing for the succeeding year. A large part of the profit is kept by the contractors, leaving very little for the fishermen. A long-term leasing policy or direct management of the reservoirs by the cooperatives is more desirable from conservation point of view and to ensure a sustainable yield.

Reservoir fishermen constitute one of the weakest sections of the society. They are exploited by the middlemen and money lenders, and they receive a very low price for their catch. The reservoir fisheries need to be brought under the fold of cooperative societies, which can take care of their credit needs, market their catch effectively and provide all necessary infrastructure. This is possible only with a strong help and participation from the State.

Figure 6.1. District-wise distribution of reservoirs area (ha) in Madhya Pradesh