An overview                                                                                                                                   

 Since independence harnessing the state’s various rivers for power generation and irrigation has been the main focus of developmental activities in the state of Himachal Pradesh. This has resulted in the emergence of number of river valley projects through out the state with a primary objective of power generation, irrigation and other activities. Though the water bodies so created by constructing dams across the river offer tremendous potential for fish growth yet act as barrier for the migration of fish for breeding / feeding purposes. The major water bodies so created are Gobind Sagar, Pong and Chamera besides many more small projects are continuously adding to existing ones. Though   the small water bodies due to their draw down character are highly difficult to harness, the major reservoirs are developed to this stage by adopting three   pronged strategy comprising  of selection of appropriate mesh size of fishing gear, increased fishing efforts and stocking support  by suitable varieties. Gobind Sagar has recorded fish production from meagre 25kgs/ha to as high as 120 kgs/ha. As a sequel to increased productivity the fishing operation has also become remunerative enough to sustain these fishermen.

Though, essentiality a combination of fluviatile and lacustrine system the reservoirs reveal a certain characteristic of their own, the two characters co- exist in reservoirs depending upon the temporal and spatial variations of certain habitat variables. In general the lotic sector of the reservoirs sustain a fluviatile biocoenos where the lentic zone and bays of the reservoirs harbour  pelagic fauna . During monsoon due to heavy inflow of water a considerable  part of the standing crop of  biotic communities at the lower trophic level disturbs the natural primary community succession. The sudden level fluctuations also affect benthos by exposing or submerging the substrate. All these factors obviously affect the seasonal fluctuations in the centers of the reservoirs. Since each eco-system differ very widely in limno- chemical aspect, hence each reservoir is discussed separately.

Reservoir viz. Gobind Sagar and Pong of Himachal Pradesh with mean water spread of 25,000 ha constitute an  important fishery resource of the State. The development of fisheries on scientific lines in these ecotopes have shown its tremendous potential for food production and generating employment. In view of series of management measures taken by the State Fisheries Department, a total of 32184.06 tonnes of fish valued Rs. 7862.9 lakhs was harvested from these two impoundments during (1985-86 to 2010). This has also helped in providing viable vocation to over 5,000 fishermen families, constituting about 20% of dam’s oustees on sustained basis. The State Government too, realised an income of Rs. 1357.6 lakhs by way of royalty, fee and fines etc. in view of fishing activities. During 2009-10 alone a total of 1515.27 tonnes of fish valued Rs. 841.90 lakhs was harvested by 3586 fishermen from Gobind Sagar & Pong Reservoirs. The department’s income during a single year alone (2009-10) was Rs. 228.59 lakhs.

Further, while Gobind Sagar is maintaining an unique distinction of highest per ha fish production (over 48 to 100 kg/ha.) for over one decade, the Pong Reservoir fishermen are getting highest per unit price of their catch at landing sites (Rs. 41-83/ kg.) in the country. In view of these two characteristic features while the fishermen of Gobind Sagar have benefited by continuous increase in total catch over the years, the fishermen of Pong reservoir got benefited by steep increase in the price of the harvest. The fish fauna of both these water bodies differ widely, while Gobind Sagar is exclusively carp reservoir, the Pong Reservoir is predominantly a catfish reservoir.

Gobind Sagar Reservoir

Built due to daming of river Satluj, the Gobind Sagar Reservoir came into existence during mid sixties. The pristine streams of river Satluj harboured 51 species of fishes including exotic trout, snow trout and several species of hill stream fishes. Mostly these species were unique due to sub-temperate climate and the zoo-geographic affiliation to the Himalayan region. The upper reaches of Satluj and its tributaries were particularly rich in Tor putitora , Labeo dyocheilus, L. dero and Schizothorax species. The available species belong to nine families.

1. FAMILY CYPRINIDAE

   Barilius bendelisis, B. vagra, B. barila, B. modestus, Oxygaster bacaila, Rasbora daniconius, Carassius auratus, Cirrhinus reba, C. mrigala, Crossocheilus latius, Catla catla, Labeo dero, L. dyocheilus, L. bata, L. calbasu, L. rohita, Cyprinus carpio var. communis, C. carpio var nudus, C. carpio var specularis, Schizothorax richardsonii, S.plagiostomius, Ctenopharyngodon idella, Hypophthalmicthys molitrix, Tor putitora, Garra gotyla gotyla, G. lamta , Puntius sarana, P. ticto, P. chola and P. sophore.

2. FAMILY COBITIDAE

   Biota dario, B. birdi, B. lohachata, Noemacheilus botia, N. rupicola, N. monatanus, N. kangrae and N. horai.

3. FAMILY BAGRIDAE

   Mystus seenghala and M. aor.

4. FAMILY SCHILBEIDAE

   Clupisoma garua

5. FAMILY SISORIDAE

   Glyptothorax pectinopterus and G. cavia

6. FAMILY BELONIDAE

   Xenentondon cancila

7. FAMILY OPHIOCEPHALIDAE

   Channa gachua and C. punctatus

8. FAMILY MASTOCEMBELIDAE

   Mastocembelus armatus armatus

9. FAMILY SALMONIDAE
   Salmo trutta fario

    

The following are the commercially important fish in order of their abundance: H. molitrix, C. carpio var. specularis, C. catla, T. putitora, L. rohita, L. dero. L. calbasu, L. bata, L. dyocheilus, C. mrigala,. W. attu and M. seenghala.

Gobind Sagar

INDIGENOUS CARPS:

A perusal of indigenous carp composition from 74-75 to date indicate that their proportion increased till 78-79 where after it declined each year barring C. catla which showed some increased spurts. The percentage of indigenous carps during 97-98 was 7% only. All the four Indian major carps viz. L. rohita, C. mrigal, C. catla and L. calbasu are present in the reservoir. L . rohita a commercially highly valued fish has undergone a steep decline in the catches since 1980-81 and for the last 15 years (1995-96 to 2009-10) maintaining a low profile range from 4-16 tonnes each year. C. mrigala too has suffered the same fate and is contributing 1-6 tonnes for the last 15 years. L. calbasu however, never got established in the reservoir and quantitatively ranged between 1-2 tonnes each year. C. catla has virtually maintained a steady position in the reservoir. Despite being opined by many workers that silver carp would eclipse C. catla, the fact is far from truth. While during 1986-87, 20 tonnes of C. catla was harvested from the reservoir, the production during 2009-10 was 74.43 tonnes accounting an increase of 272%. The yearly average during the last 23 years was 69 tonnes.l. rohita has shown production of 3.46 tonnes during 2009-10 as an impact of stocking

MINOR CARPS:

The minor carps in the reservoir are represented mainly by hill stream species

L.dero,L.dyocheilus, L. bata, C. reba and Puntius sarana. The percentage composition of these fishes increased in the reservoir till 1982 and thereafter they started to decline. The catches during 1995-96 to date ranged between 3-4 tonnes per year which is virtually insignificant.

EXOTIC CARPS:

The three Chinese Carps viz, Silver carp, Grass carp and Common carps constitute the exotic fauna of the reservoir. The cumulative percentage of these three carps has increased from 17.4% to 88.3% from 1976-77 to 2009-10 with silver carp alone contributing as high as 67.6% of the total production during 2009-10. In terms of weightage, exotic carp production was 963.36 out of the total production of 1090.89 tonnes. Silver carp got an inadvertent entry in the reservoir during 1971 by inundation of one of the fish farms of the department when 47 Silver carp specimens ranging from 290-530 mm were washed out. The species started appearing in the catches during 1997-98 and specimens of 300 mm size appeared in 1976. During 1977 there was substantial catch of 10 tonnes of silver carp, although this accounted only 1.4% of the total reservoir landings. In view of congenial water qualities, wide feeding spectrum and high fecundity, silver carp continued to proliferate and during 2004-05 the landing reached to a level of 1023 tonnes. The maximum landing were recorded from lentic sector of the reservoir where the water was comparatively warm. The grass carp, however failed to establish in the reservoir presumably due to absence of weeds and the productivity ranged from between 6-11 tonnes which is highest so far  only during 2001-02 to 2009-10. The total production of silver carp during 2009-10 was 737 tonnes.

The silver carp fish use to migrate upstreams in Satluj River for its breeding. However with the construction works of Kol Dam, fish was denied migration movement for its breeding. Not only this but heavy load of silt below Koldam also destroyed its juveniles besides feeding grounds. its production sharply came down to 101.00 M.T. during the Year 2005-06. Fish seed of this species was stocked in the reservoir from extraneous source as a measure to increase its production. Fish production has revived to 737 M.T. during 2009-10 which constitute 67.5% of total fish production.                                                           

Mirror carp contributed significantly among the fish catches of Gobind Sagar. This fish has established well as indicated by its composition in the total landing. Regular stocking are being carried out by the department for sustained production of the species. However, being bereft of weeds, which serve as substrate for sticking of mirror carp eggs, auto stocking has not been observed in the reservoir. The landing of mirror carp ranges 51 to 215.33 tonnes from 1982-83 to 2009-10. During 2008-09, the landing were of the order of 189 tonnes and during 2009-10 the landing were of the order of 215.33 tonnes.

CARNIVORE FISHES:

The major carnivore fishes encountered in Gobind Sagar reservoir are Mahseer (T.putitora) and M. seenghala. During last 10 years the cumulative percentage ranged from 2.4 % to 6.2%. The highly voracious M. seenghala has kept a low profile in the catches as reflected in catch structure. The low proportion of catfish has indeed helped in fast propagation of carps despite the absence of ideal habitat for spawning. T. putitora which used to form a dominate fishery of Satluj river prior to impoundment has markedly declined. The catches have fluctuated between 8 to 46 tonnes for the last 15 years, the lowest (8 tonnes) during 2001-02. The landing of these species during 2009-10 recorded as 13 tonnes of seenghara and 29.14 Tonnes of Mahseer Fish..  The major factors attributed to decline in mahseer catches are (i) denial of migration for breeding, (ii) large scale killing of juvenile specimens and (iii) absence of insects and weed fauna in water body which forms the preferred food of mahseer. However, the department has taken action by amending the Fisheries Act and raising the allowable size for catching fish from 30 to 50 cm. so that specimen over one kg could only be caught.Now Mahseer fish production has started showing slight improvment.

AVERAGE SIZE OF MAJOR SPECIES:

A review of the fluctuation of major species being caught in the reservoir for the last 27 years (1982-83 to 2009-10) indicate that among carps the average size of L. rohita, C. catla, C. mrigala and L. calbasu has ranged from 1.2 to 5.1, 3.5 to 11.00, 1.2 to 2.6 and 0.6 to 1.23 kg. respectively. Where as During 2006-07 the average size respectively of these was 1.50,7.2,1.42 and 1.23 kg while in 2009-10 it is 1.93,2.32,1.37 and 0.8 KG .. Among exotic carps the average size of Silver carp and Mirror carp ranged between 3.20 to 9.6 and 0.9 to 2.70 respectively for the same period. Silver carp despite 101% decrease in landing during last Eight years 2002-03 to 2009-10 is maintaining a steady average size of 3.2 to 3.95 kg. The species has shown rise of 206% in fish production during 2009-10 as a result of Scientific management. Similarly the catches and average size of mirror carp have increased by 30% in  the reservoir for the last eight  years averaging  0.7 to 1.07 kg. respectively. As far as carnivores are concerned, M. seenghala ranged between 9-12 tonnes while their average ranged to 1.2 kg. In case of Mahseer the average size has varied within  ranges of 0.6 to 1.8 kg. for the last ten years ( 1996-97-to 2009-10). During  year 2009-10 production has gone up to 13.63 in tonnes.

FISH YIELD CATCH EFFORTS:

The fish yield from reservoir has ranged from 37.7 to 120 kg/ha for the last 32 years (1976-77 to 2009-10). The highest was recorded during 2002-03(1202 tonnes) while lowest during 1986-87 (377 tonnes). In the year 2009-10 fish yeild is 109.09 KG/ha In fact starting from 1986-87 when an all time low landings were recorded there is a constant rise in production each year reaching to a level of 1202 tonnes during 2002-03. The major reason attributed to persistent increase in catches are strict conservation, imposition of closed season, providing better quality subsidized nets to fishermen and initiation of fishermen welfare schemes. But during the last four years  (2003-2007) construction of Koldam on Satluj river and fluctuation  in reservoir water level (F.R.L.) reduced value of water in the rivers joining reservoir, heavy siltation are possibly the causes for the decrease in fish production from the reservoir. Due to concreted efforts from department during the year 2009-10 the fish production of Gobind Sagar reservoir recorded as 1090.89 highest in last five years.

REVENUE:

The revenue earned by the Fisheries Department from Gobind Sagar Reservoir falls under three categories.

• Royalty @ 15% of the price of the fish caught;
• License fee charged annually from all fishermen belonging to various Co-operative Societies @ 100/- each;
• Fines realised from the poachers for conducting illegal fishing or other offences indicated in the Fishery Rules; auction and sale of confiscated fish incorporates the revenue realised by the department during various years.

 SPECIES INTRODUCTION:

Prior to construction of dam, the cold water of upper reaches of river Satluj used to harbour 51 species of fish of which T. putitora, L. dero, L. dyocheilus, Schizotharacids were dominant ones. The main question which confronted the policy makers during early stages of fisheries development in the impoundment was whether the resident indigenous species of Satluj would be able to effectively populate in the lacustrine condition of the reservoir or whether new species are to be stocked to utilize the new habitat.

It was a general consensus among the landing limnologists that none of the indigenous rheophylic species would be able to offer viable commercial fishery and it was recommended that the reservoir should be stocked with Indian and exotic carps. Taking this into consideration the State Fisheries Department stocked 3500 gravid spawners and 0.5 million fingerlings of Indian major carps which established themselves in the reservoir and started breeding. The stocking in subsequent years continued mainly with mirror carp seed. A number of fish farms were set up in the State for this purpose with the main goal of producing the seed and their transplantation in the reservoir.

RESERVOIR MANAGEMENT:

During the first phase of reservoir development in 1964-75, the Department issued license @ Rs. 10/- per gill net and fishermen were free to dispose their catch as they wished. This, however, failed to develop a commercial fishing of appropriate size and hardly benefited the fishermen. During 1976, a fishing policy was formulated and implemented. As a first step all the fishermen were organized under Co-operative Societies. The fish caught by the fishermen were now brought to the fixed landing centres for handing over to the Fish Federation, an apex body entrusted solely for the sale of fish. The Federation was free to sell the fish either at their own retail outlets or to the contractors. This Federation, an intermediary body between the societies and contractors, was made fully responsible for making payment to the fishermen at the rate fixed each year during the beginning of the year. Due to some management problem the Federation has been closed during 2006. Now societies are providing their produce at the rates fixed at the beginning of the year to contractors. The department’s role was also made specific. Seed stocking, conservation, watch and ward, implementation of Fisheries Act /Rules, monitoring of catches, initiation of welfare schemes, providing subsidy and arranging loan were made as the major responsibility of the department.

FISHERMEN AND THEIR ORGANIZATION:

At present there are 3881 fishermen recruited from 5500 oustees settled near the reservoir. This accounts for approximately 25% of the total fishermen population. Prior to the impoundment of a subsistence fishery of inconsequential nature existed in the rivers and streams, but with the formation of the reservoir the lucrative fishery started attracting a large number of fishermen and other oustees who lost their property with emergence of the reservoir. The local fishermen who used to fish in shallow rivers and streams with primitive gears found them ineffective in the deeper waters of the reservoir. The Fisheries Department then initiated training in the use of deep water fishing gear and boats. The income of the fishermen operating in the reservoir inspired other oustees of various communities to adopt fishing as a profession and by 1978 the total number of fishermen reached 1280. Besides direct employment to approximately 1000 families, the state provided livelihood to about 1000 additional families engaging in helping the fishermen carrying/ transportation, packing of fish, fishing crafts/ gears, repair, sale of fish etc.

The fishermen of Gobind Sagar are full time licensed fishermen and member of Co-operative Societies and have their own boats. On an average 40% of the fishermen have some education. The monthly income ranged from Rs. 800 to 3000. On an average, each fishermen has one boat, usually of the size 16ftx3ftx2ft, costing approximately Rs. 20,000.. The fishermen use mainly nylon gill nets. Each fishermen has on an average 3-4 gill nets of 100 to 140 mm mesh size which lasts about 1-2 years.

REMARKS:

The Gobind Sagar offers a classical example of exploiting the large reservoirs created in view of completion of river valley project for job generation and production of high quality animal protein i.e. fish. The reservoir has in fact created a history of maintaining highest per unit fish production in large reservoirs for the last two decades in the country. This could be made possible by adopting a sound management and development policy which inter alia include formulation and implementation of Fisheries Act, regular stocking, providing assistance to fishermen for pursuance of fishing equipment, strict enforcement of closed season and mesh size regulations etc. As per available figures the last  years a total of 1090.89 tonnes fish valued Rs. 471.14 lakhs was harvested from Gobind Sagar reservoir. The department earned a revenue of Rs. 73.86 lakhs in terms of royalty , fee and fines etc. Further, 3881 direct and 2388 indirect jobs were made available in view of these fishing operation.

 PONG RESERVOIR

Impoundment across river Beas the Pong Reservoir with a catchment area of 1256 sq. kms. and mean water spread of 15662 ha. came into existence during 1974. Trial fishing was resorted by the department soon after its filling but during initial years the catches were dominated by rheophlyic species belonging to family Salmonidae, Cyprinidae, Gobitidae, Sisoridae etc. However, due to tremendous biogenic capacity of the reservoir and systemic seed stocking, undertaken by the department ,over a number of years with Indian carps and mirror carps, the catch structure of the reservoir was altered and carps started accounting as high as 50-60% of the catches. During 1987-88 per ha yield of the reservoir also touched a level 53 kg/ha with cat fishes, and carps accounting 70% and 30% in the landing. The limnological studies of the reservoir has shown a positive curvilinear relationship between standing crop and total alkalinity. The hypsographic curves indicated inverse relationship between volume of water and fish production.

As stated the commercial fishing in the reservoir was initiated soon after its emergence. The total catch during 1976-77 the first year of fishing operation was 98 tonnes and increased progressively attaining a peak of 797 tonnes during 1987-88, fluctuating with in a narrow range of 486-596 tonnes. During 1988 the incessant rains and flood forced the dam authorities to open flood gates which caused large scale escape of fish from the water body, obviously affecting the landing in the subsequent years. Subsequently the influre of migratory birds to the reservoir also increased. The reservoir has been declared International Wet Land (Ramsar Site) . On an average 1,50,000 migratory birds are now visiting the reservoir every year for their winter sojourn. Many families of the birds have become permanent residents of the reservoir due to adequate food & shelter. Approximately 40% of these winged visitors are fish eaters, some of them like black cormorants are the various fish eaters. this has reduced the carp fish populations in the reservoirs. The reservoir catches are now dominated with catfishes like Singhara and the catches have  plummeted to 421.48 tonnes during 2009-10. Most of the carp seed being stocked by the department in this water is being used as food either by aquatic birds or catfishes.

FISH STOCK COMPOSITION

A total of 27 species (sub-species, varieties) belonging to six families have been encountered in the Pong reservoir.

1. FAMILY CYPRINIDAE

   Barilius bendelisis, B. Vagra, Cirrhina. mrigala, Crossocheilus latius, Catla catla, Labeo dero, L. bata, L. rohita, Cyprinus carpio,Schizothorax richardsonii,Tor putitora, Puntius sarana, P. ticto.

2. FAMILY COBITIDAE

   Botia birdi, Noemacheilus kangrae..

3. FAMILY BAGRIDAE

   Mystus seenghala and M. aor,Bagarius bagarius.

   FAMILY SILURIDAE
   Wallago attu

4. FAMILY SISORIDAE

   Glyptothorax pectinopterus and G. gharwali.

5. FAMILY BELONIDA

   Xenentodon cancila

6. FAMILY OPHIOCEPHALIDAE

   Channa marulius C.cephalus, C.striatus

7. FAMILY MASTOCEMBELIDAE
   Mastocembelus armatus armatus

QUALITATIVE AND QUANTITATIVE FLUCTUATIONS:

A perusal of indigenous Carp composition in the total catches from 1976-77 to 1997-98 indicate that they dominated over carp fishes till 1991-92 where after catfishes virtually left the ground. During 1991-92, the carps viz.L.rohita,C.catla, C.mrigala, L.calabasu accounted 46.3% (225 tonnes) of the total catches while cat fishes viz. M. seenghala, W.attu accounted 37.9% (60 tonnes) and other 2.4 %(12 tonnes). Against this during 2009-10 the percentage composition of indigenous carps, cat fishes, mirror carp, mahseer and others was 25.4% (107 tonnes), 58%(246 tonnes), 5.9%(24 tonnes), 9% (38.31 tonnes), 1.08% (4.58 tonnes) respectively.

Among the Indian major carps,. L. rohita is the dominant fish encountered in the reservoir. The highest catch (491 tonnes) of IMC fish was encountered during 1987-88. For the last Eight  year 2001-02 to 2009-10 the catches have fluctuated from 32-73 tonnes. During 2007-08, the landing of L. rohita was 10  tonnes which has increased to 35.67 tonnes during 2009-10. C. catla has always kept a low profile in the reservoir the maximum (34 tonnes) were encountered during 1994-95. The catches during 2006-07 were 2.6 tonnes whereas it has increased to 6.89 tonnes in 2009-10 . C.mrigala has suffered a marginal  decline. The catch of Mrigal is showing an increase which is 64.44 tonees in 2009-10. L calbasu  used to account significantly in the reservoir during eighties the highest being 85 tonnes during 1982-83 and 0.416 during  2009-10.

Pong reservoir may be categorized as a Mystus reservoir. M. seenghala is showing constant increase during the last 10 years, the highest catch (324 tonnes) was recorded during 2005-06 accounting 75.52% of the total catch. . During 2009-10 fish catch of M. seenghala was recorded  246 tonnes accounting 58.3% of total landings. 

Mirror carp composition is quite erratic in the reservoir presumably due to the fact that ideal breeding grounds are non-existent in the water body. However, regular stocking has helped in the revival of mirror carp fishery and for the last eight years there is progressive increase in its composition and from an all time low of two tonnes during 1992-93, the catches have increase to 39 tonnes during 2004 During the year 2009-10 the catch of  mirror carp was  recorded 24 tonnes.

Mahseer is a highly precious and sought after fish of the Pong reservoir. Its probably the only reservoir in the country which provide the opportunity of mahseer angling. The catches of mahseer in the reservoir has shown remarkably consistency during the past ten years and landing have fluctuated between30-39 tonnes. The highest catches of mahseer102 t  were recorded during 1982-83.During 2009-10 total landing of mahseer was 38 tonnes i.e. 9%.

AVERAGE SIZE OF MAJOR SPECIES:

An analysis of data for the last 26 years (1983-84 to 2006-07) indicate that average size of all species of Indian major carps have progressively increased in the water body. L.rohita, the principal fish has registered an increase of 1.4 to 7.76 Kg, the average during the last three years being 3.68 Kg. Catla catches are more pronounced, the average size being 5.77 Kg during 2009-10. During the same period C.mrigala and L.calbasu, too have registered increase in average size and the respective figures in terms of average size for the last four years ( 2003-04 to 2006-07) were 1.55 & 2.51 Kg respectively.In 2009-0 average size of Mrigal & calbasu are 1.66 and 1.41 KG respectively. Mirror carp, however have shown a steep decline in average size during last few years. This may be attributed to spurt in catches, while during 1995-96 the total landing of mirror carp was three tonnes with average weight of 1.6 Kg. this obviously was the result of intensive stocking of this species. Mahseer has kept steady profile in terms of average size in the reservoirs. For the last 25 years the average size has ranged between 1.2 to 1.6 Kg while the total landings have fluctuated between 10 to 102 tonnes during 1995-96 to 2009-10 and the average size of mahseer was 1.3 Kg. the average size of the another species encountered in the reservoirs viz. L.dero, W.attu, Channa species were 0.4, 4.3 & 1.8 Kg. respectively.

FISH YIELD, CATCH EFFORTS:

An analysis of production figures for the last 28 years indicate that there is consistency in the yield rate, which works out to 30 Kg/ha which  ranged between 6 to 53 Kg /ha.The average yield during 2009-10 was 26.34 KG/ha  Kg/ha.

REVENUE:

While the fish landings of Pong reservoir have shown a consistency during the last two decades, the value of fish caught has increased significantly mainly attributed to quality of the catch. The value of fish caught increased from 5.18 to 267.42 lakhs. During 1995-96 the average value of fish catch was 154 lakhs. During 2009-10 fish worth 369.20 lakhs was harvested from the reservoir.

As far as department revenue is concerned, the revenue of Rs. 63.18 lakh was recorded during 2009-10  & the respective contribution by royalty license fee & fines etc. was 87.6%, 3.2% & 3.10% respectively.

SEED STOCKING:

Prior to the construction and completion of the reservoir, detailed study on ecology and fisheries of river Beas had never been done(Sehgal, 1998). However, Howel (1916) recorded Oreinus sinnatus, S. richardsonii & Glyptosternum striatus three major fishes of river Beas from Beaskund to Largi-a stretch of approximately 150 Km. Later, Singh (1982) listed T.putitora, S.richardsonii, L.dero & W. attu from Beas river. The creation of the reservoir while at one hand has created a perennial sources of water body but on the other hand certain migratory species started competing to retain their position in the ecosystem. Of these, three most important Golden mahseer (i.e. putitora) Snow trout (S.richardsonii) & L.dero. The mahseer which had its migratory run up to Sultanpur near Kullu has disappeared in this area after the construction of Pandoh Dam. The other affected species are S. richardsonii & L.dero. while the former could not establish in the new environment, the later is struggling to retain its progeny in the reservoir.

The stocking programmes in Pong reservoir were initiated during 1974-75 when the first consignment of 1.30 lakh fry of mirror carp were released. Since then a regular stocking programme has been undertaken. Stocking has been mainly confined to the seed of mirror carp and Indian major carp, L.rohita, C.catla and C.mrigala. the seed of other species viz. T putitora. Schizothorax spp. and L.dero could not be made available due to absence of any large scale seed production technologies. The State Fisheries Department has set up or improvised fish seed farms located near the reservoir site namely Kangra, Deoli, Nalagarh, Sultanpur and Alsu. Seed stocking is being done with a seed size more than 40 mm.After the completion  of construction work of the envisaged Mahseer farm in Mandi district it is hoped that reservoir shall be able to receives regular supply of mahseer seed.

RESERVOIR MANAGEMENT:

With a view to enforce effective management and formulate a concerted approach of fisheries development in the reservoirs, a State level ‘Reservoir Development Committee’ was set up during 1976. As a first step it was decided to bring all fishermen under a cooperative fold and only a member of the Co-operative Societies would be permitted to operate nets in the water body. Three Societies with the total membership of 303 fishermen were registered during 1976. By 2009-10, the number of societies decreased  to 15 with membership of 2825 fishermen. No license fees was charged from the fishermen till 1981-82, but later an annual license fee of Rs. 50/- was levied on each gill net of 80 m. length. The department also charges 15 % royalty on the price of the fish caught by each fishermen. The permitted gears are  gill nets and rod and line only.

For sale of fish the practice of appointing contractors by open auctioning at the beginning of each year was started. The fish caught by the fishermen are required to be brought to the fixed landing centres (15 in all). the representatives of the contractors receive the fish at the fixed landing centres while the departmental staff charges the royalty and record the quantity of the catch species wise. The contractors make weekly payment to the societies besides keeping a lumpsum or fix deposit to be confiscated in the eventuality of any default. The societies make the payment to fishermen after deducting a marginal commission ( 5.0 to 7.0%) which varies between societies and fixed each year in the general meeting of the societies. To avoid conflict between the societies regarding the area of operation, the reservoir is divided into eight beats demarcated on the basis of area and productivity of water body apportioned for each societies. Fishermen who are members of the co-operative societies are issued annual license through the cooperative societies by the respective fisheries officers of the landing centres at the beginning of each year.

FISHERMEN AND THEIR ORGANIZATION:

Presently there are 15 fishermen co-operative societies in the reservoir. There are 2825 active fishermen recruited from 4000 oustees settled near the reservoir. This account for about 30.4% of the total population of reservoir fishermen. Prior to the impoundment of the river Beas, a subsistence fishery of inconsequential nature existed in the river and adjoining streams and the average catch hardly exceeded 2 to 4 kg. fishermen per day, but with the formation of reservoir, a lucrative fishery started attracting large number of fishermen and the oustees who had no other viable means of livelihood. The fisheries department initiated training courses for operating gears in the deeper waters for fishermen. This, however, inspired large number of oustees of various communities to adopt fishing as a profession. Beside direct employment to over 2014 fishermen, the fishing activities provide indirect job to over 1000 families engaged in helping fishermen, carrying/ transportation, packing of fish, weaving and mending of gears, marketing etc.

The fishermen in Pong are mostly full time fishermen. On an average, 30% of the fishermen have education up to primary level. The monthly income ranges from Rs. 500-1200/- per month which has gone to Rs 1500 during 2009-10. On the average, each fishermen has one boat, usually of the size of 5.0x 1.0x 0.7m, costing approximately Rs. 30,000/-. The fishermen normally use gill nets and each one has on average 3-4 nets of 80.0m x 8.0m of length and varying from 80-140 mm mesh size. The minimum allowable mesh size for economically important species are fixed by the department.

Assuring highest prices of their product to the fishermen is one of the major concern of the department. The efforts made on these lines help the fishermen to ensure maximum price of their catch.

The fisheries department has initiated a number of welfare schemes for the benefit of fishermen. 50% subsidy is provided by the department to a maximum of Rs. 3000 for the purchase of fishing gear and craft and tents. The department also arranges procurement of these equipment to meet the needs of the users. A personal Accident Insurance Scheme has been initiated on free premium of Rs. 30/- year. In case of accident  the insured person’s family gets an amount of Rs. 100,000. A risk Fund Scheme has also been initiated under which fishermen are compensated to the tune of 33% for losses such as blowing and sinking of boats or nets. Further, during the period of closed season (1st June – to 31st July), a subsistence allowance of Rs. 400/- paid by state Govt. Rs. 400/- by Central Govt. per month is paid under a Relief Scheme. For this the fishermen has to pay Rs. 400/- contribution on equal installments of Rs. 40 each for ten months of the fishing season 1st August to 31st May.

REMARKS:

The Pong reservoir depicts a classical example of using reservoir for food production and generating employment avenues. Fisheries development in Pong reservoir has helped in settlement and providing livelihood to families uprooted due to the impoundment. Though primarily formed for power generation and irrigation purpose, approximately 4178 tonnes of fish valued at Rs. 1978.69 lakhs was harvested from the reservoir during the last 10 years (1996-97-2006-07). During  2009-10 fish worth Rs. 369.20 lakhs was harvested from reservoir. Among the positive decisions taken by the management, the most important was to stock the reservoir with seed of Indian major carps. This helped in establishment of L. rohita, contributing as high as 42.5% during 1989-90. But its cathces dipped down due to devastating floods of 1988.In 2009-10 its catch was just 35.67 MT which is 8.46% of total catch. The enactment of State Fisheries Act, 1976 (Act No, 16), enforcement of mesh size regulation, organization of fishermen under the cooperative fold, imposition of closed season, settling of fishermen during the initial stages from outside the State, initiation of fishermen welfare scheme etc., were other well conceived measures which helped in boosting the reservoir’s fisheries activities and providing vocation to the displaced inhabitants of the reservoir.

The catch spectrum of the reservoir altered considerably during the course of years. During the initial years the catch was mainly dominated by M. seenghala, T. putitora, L. dero, W. attu, C. mrigala and C. carpio. While L. rohita had considerable degree of success in getting established in the reservoir, the same is not true for other species such as C. catla, C.mirgala and C. carpio.  The probable reasons which attribute to non-establishment of mirror carp are absence of weed in the water body, dominance of predatory fish fauna and browsing habit of the species. The reasons for non-establishment of C. mirgala and Catla catla defy explanation and require detailed scientific studies. In the earlier years, after the formation of the reservoir, the dominance of indigenous fishery is more pronounced. During 1982-83, M. seenghala was the most dominant fish (28.45%) followed by Mahseer (20.4%) L. calbasu (17.0%) Wallagu attu (7.0%), C. mrigala (5.4%), and Mirror carp (5.8%). However, L. rohita was far from recognition and it formed hardly 0.4% of the catch.

Subsequently the catch spectrum altered widely owing to the effect of the dam, the establishment of exotic varieties, vagaries of monsoon and fluctuating water level of the reservoir. The stocking of L. rohita was initiated during 1974-75 and the species soon established, yield 83.9 tonnes (15.2% by weight) by 1985-86. In 1987-88, the contribution increased to 42.5%. Thereafter, there was a decline in the fishery due to heavy escape of stock. During 2009-10 catch recorded 35.67 tonnes i.e. 8.4% of total catch.

A remarkable feature of the reservoir is the establishment of carps despite dominance of carnivores like M. seenghala. W. attu and T. putitora. Their cumulative percentage was 55.8 during 1982-83 against 38.5 during 1989-90 which has further dipped to 25.47% in 2008-10. Compared to this, the percentage of herbivore fishes was 43.0 during 1982-83 against 56.6 during 1989-90.

Maintaining a high sustained yield is the backbone of the reservoir fisheries management. The department, while giving it a priority attention, has carefully developed a monitoring system. At each landing centre, fisheries officers, field assistants, sub-inspectors and helpers have been posted, who weigh the landed fish and species-wise record is maintained. They also maintain strict surveillance on mesh sizes, apprehended poachers and take action against them. Further in view of a long shoreline, the surveillance of the reservoir places a great demand on the limited man-power of the department. The situation becomes extremely acute during the closed season when fish are scarce in the market and the prices shoot up. The concentration of fish in the shallower areas for breeding makes them vulnerable to poaching. The department sets up a number of field camps during the closed season at such vulnerable points to control the poachers. The department has also set up flying squads in order to reinforce the surveillance. A conversation unit with a speed boat moves round the clock in the reservoir to protect the spawning grounds. In this way the department has been able to control the illegal fishing in the reservoir to a considerable extent. The Himachal Pradesh Government has enacted the Fisheries Act, 1976, and fishing during closed season has been made a cognizable non-bailable offence, inviting imprisonment upto two years or  fine upto Rs. 3000/ a both simultaneously-. Further, the watch and ward staff has been given full power to seize fishing gears and to forfeit or confiscate fishing devices and fish.

Adventure

Himachal Pradesh the abode of gods the land of snows a tourist’s dream and delight, is also an angler’s paradise. It has some of the finest trout streams in the north. The Pabbar in the Rohru valley, the Baspa in the Sangla valley, the Uhl in the Barot valley, and river Beas and its tributaries in the Kullu valley, abound in both brown and rainbow trout, while many rivers and streams in the Kangra valley are well-known for mahseer fishing. Each of these rivers has 32 to 40 km of angling reserve area, where one can fish with joy.

 Angling rules are liberal and the fee nominal. Angler is permitted to catch six trout a day on each license; however a trout should not be less than 40 cm in size. Trout fishing season lasts from1st November to 28^th February each year.

 Trout Fishing:

 Let us first discuss the places and the rivers and the streams, where one can find trout, easily.

 Rohru:

 1500 mm, 120 km from Shimla, on the right bank of river Pabbar, is an important fishing centre. 50 km up-stream from Rohru, and situated on the left bank of Andhra, a tributary of Pabbar,

 Chirgaon is another fishing centre, besides being an ideal place for relaxation. The other places which are easily approachable from Rohru, and are known for providing good fishing opportunities are Seema (5km), Mandil (10km), Saandhsu (17 km), Tikri (21km) , and Dhamwari (24 km).

 The river Baspa which takes its origin from the glaciers of the great Himalayan ranges, and remains practically clear except during the monsoon, flows through the Baspa or the Sangla Valley, which is one of the most beautiful valleys in the western Himalayas. Baspa makes a series of rapids, and has many nice pools for trout. Surrounded by high mountains and providing a splendid view of the majestic Kinnar Kailash, Sangla, a populous village (2,621) m with well furnished PWD and Forest Houses, could be a convenient place for fishing in this valley. Kupa and Badseri, which are just a few km from Sangla are also good spots for trout fishing. A temple and a Buddhist gompa and the ancient Kamru fort are some other attractions which the anglers should not miss. Sangla is 250 km from Shimla and is well connected with regular bus services.

 Barot (Mandi) 200 km from Shimla and 75 km from the Mandi town is known not only for its picturesque water reservoir and scenic beauty, but for trout fishing also which abounds in the Uhl river, a tributary of river Beas. Some of the finest fishing spots are located at Luhandi, Puran hatchery, Lachkkandi, Tikkar, Balh and Kamand. Besides Barot the entire reservoir from Pandoh Dam to Aut on the Mandi-Manali national highway is also considered good for trout fishing.

 A part from being one of the most beautiful valleys in the Himalayas, the Kullu valley offers some ideal opportunities for trout fishing in the river Beas, which meanders through it, and in its larger tributaries, like Sarveri, Parbati, Sajoin and Phojal. The Sainj and Tirthan rivers, which form a tri-junction with the Beas a few hundred meters downstream from the conspicuously located PWD bungalow at Largi, are also trout streams. The main Kullu valley right from Manali to Bhuntar provides some excellent pools for fishing especially at Patlikuhl, Katrain and Raison. Trout hatcheries have also been developed at Patlikuhl and Bathad. The Parbati valley, with its scenery generally on a wilder and more impressive scale, with dense forest to the hillsides, affords some excellent trout prospects throughout the course of the river Parbati from Manikarn to the confluence at Bhuin, Kasol, 5 km before Manikaran, charmingly situated on an open space which slopes down to a broad expanse of clean white sand at the end of the main river, makes a first rate halting place with every prospect of some really good spot. Chandigarh and Delhi and with many other places in the outside the state, Kullu is also on the air map of the country with regular flights from Delhi and Chandigarh.

 Mahseer Fishing

 After having savoured the delicacies of the trout, let us now come down to the comparatively less high Kangra valley, situated in the lap of the mighty Dhauladhar ranges, irrigated with streams which descend from perennial snows, and interspersed with homesteads buried in the midst of groves and fruit trees. Kangra has been known as the home of the proverbial mighty mahseer to which effect a fairly large account of evidence is available from the vivid accounts of various anglers interested in heavy fish. The river Beas and the Pong Dam reservoir provide attractive fish grounds to the anglers. Besides mahseer, the other fish available is malhi, soal, bachwa, god shingara etc. Although there are many places and rivers and streams where mahseer is available, the following beats are considered the best.

 Sari Marog: Confluence of the Binwas tributary with the river Beas. A place known for its fantastic size of fish, with deep pools and many stones and hiding places. The approach is via Palampur, Andretta and Jaisinghpur. From Sari Marog village, a 3 km footpath leads to the spot, which entails a steep and a breathtaking climb of about 45 minutes.

 The stretch between Harsi Pattan and Nadaun: There are numerous beats on this stretch, easily accessible from the Palampur-Bhawarana-Thural road. The famous spots are the Mandh-Khad confluence, Lambagaon pool, Neogal confluence near Alampur, and Ambter, 2 km above Nadaun itself.

 Chamba Pattan: Accessible from Jwalamukhi via road. After 8.5 km this locality offers three good spots, viz. the Chamba Pattanpool, the Kaleshwar beat opposite Chamba Pattan village, and the Uppar Chamba Pattan Run. All these places offer safe catches and can’t be fished in one day.

 Kuru: Kuru village offers two fishing spots, both of which are accessible from one of the two river banks. The Kuru- Pool is the confluence of a small Khad with the Beas river, joining about 1 km above the village and forming a small bay, above and below which exceptional catches have been experienced. Access is through a 3 km- footpath from Dehra-Jwalamukhi road where a peepal tree and a small water tank is located at the rode side.

 Dehra-and Pong Dam Reservoir: Pong reservoir from Dehra to the Dam proper offers excellent fishing for mahseer almost round the year when fishing is open. The Pong reservoir can be approached from Pathankot via Jassur, from Chandigarh via Talwara, and from Dharmsala via Dehta and Nagrota Surian.

 The area of Ashni stream upto its confluence with the river Giri, falling in Solan and Sirmour district, provides enjoyable fishing opportunities. Near Solan, about 30 km away, on the Rajgarh road, passing through a valley dotted with plum orchards, fields and little farm houses, across the Giri bridge, is Gaura, once known for its huge mahseer. The place offered good spot to the erstwhile Patiala rulers and their British guests. Even today, Gaura, apart from bring a scenically beautiful place, offers good prospects for mahseer fishing. Another spot is the stretch of river Yamuna from Naught ferry crossing down stream in Ponta Sahib.

 Largi: A place located at a distance of about 7 km from Aut on National Highway-21 is an ideal trout angling spot on river Tirthan. It has a HPPWD rest House and license office of Sub-Inspector Fisheries. Himachal Government has specifically declared Tirthan river as an angling reserve and taken a historic decision not to allow any hydro power project on this river as well as it’s tributaries in order to maintain it’s aquatic biodiversity. Every year fingerlings of brown as well as rainbow trout are stocked in this river by the department. Almost each & every angler went satisfied in the past after fishing in a stretch of 20 kms upstream Largi.

Manmade lakes & reservoirs:

Planning and development

 Industrial and subsistence fisheries

The potential fisheries of a new man-made lake & reservoir are of three kings: industrial (commercial), subsistence, and recreational. Together they constitute one of the earliest and most easily gained return from a man-made lake. The first two are considered here; recreational or sport fishing will be taken up under the heading of tourism. There is no problem of conflict among these three types of fishing in large man-made lakes that is without solution if adequately studied. For example, although it has sometimes been alleged that the quality of sport fishing may be adversely affected by commercial fishing, under proper management systems the two types can be complementary and can greatly increase the net economic benefit derived from the fishery resource.  

As with most other secondary aspects of reservoir construction, the disciplines of fisheries and related hydrobiology should be represented at the earliest stages of planning. Fishery expertise will be required to evaluate the effect of the engineering works and the proposed land and water uses (especially the projected water regimes) on the living aquatic resources and to avoid costly losses of aquatic production.

Fairly lengthy preimpoundment research and study are required to make predictions of future fishery potential for economic assessment and planning. The components of such investigations are: 

• Species composition and relative abundance of stocks of the riverine fish population, both downstream and upstream from the proposed dam site;
• Soil types and their extent and distribution in the basin, especially in relation to the spawning grounds;
• Location and characteristics of tributary streams, including character and amount of lilt load;
• Areas and rate of siltation;;
• Extent and volume of water available for fish production, including water level regime and flushing rate;
• Thermal and chemical stratification probabilities;
• Current and historic yields by species in the riverine fishery.

 Combining this local information with experience recorded elsewhere, including testing the validity of similar estimates of production will enable a fishery scientist to make predictions of future fishery yields. Alternative predictions based on alternative forms of engineering work will assist in making the best decisions as to the location and design of the dam. Design features, which might be affected, would include: 

• Vertical location of draw-off structures, such as pen stock (sluice gate) openings;
• Need for, and character of fish passes or devices for controlling the movement of fish;
• Best water regimes for the fishery component of an economically optimized multiple-water use scheme.

Early predictions regarding the aquatic resources that may bear on engineering works and on land-and water-use planning are many. Detailed discussion follows on some of the most important of these. 

Planning for optimal development:

The fishery of a new reservoir can develop fortuitously or it can be developed on the basis of an orderly economic and scientifically conceived programme. If the development is allowed to be haphazard, net yield is likely to be far below the maximum sustainable, and overexploitation of at least some key stocks is likely to take place. Further more, fishermen are likely to become entrenched in inefficient methods of fishing and catch disposal from which it may be extremely difficult to disengage them. 

If, prior to impoundment, valid predictions are made as to the character and natural development of the fish stocks, and if the optimal manpower and investment schedule in different kinds of fishing is carefully planned, along with an adequate scheme for disposal of the catch for good or cash, then an orderly development may result. As a part of this development, a system of catch statistics to give yield and value by species in relation to fishing coast and effort must be instated as the primary indicator of the adequacy of the plan of fishery development. These statistics are also the basis for early identification of over-fishing of under-fishing of species stocks, and are therefore a first key to rational management of the resource.

It often becomes evident early in the planning of fishery development programmes that the fishermen themselves are in need of education and re-equipment. A vigorous fishery extension programme can meet this need but, to be successful, should go into operation at a very early stage of planning so as to offset the shock caused by the sudden appearance of a new man-made lake. 

Additional planning for optimal fishery development will include: 

• Appraisal of relevant aids to navigation and marine safety requirements;
• Provision of systems for landing, handling, storing, processing, transporting and marketing the aquatic produce, possibly through fishermen’s co-operatives;
• Organization of a fishery trade school;
• Development of an advisory system on the investment of venture capital in the fishery;
• Financing as required, by means of bank loans, of both the fishermen and the fishing industry. Supporting services that may need to be developed include the supply of fishing gear, boats, ancillary goods, and repairs.

 The whole plan for the orderly development of the fishery resource depends on early and vigorous interaction for planning among fishery scientists and technologists, resource economists, and engineers. 

Changes in fish fauna from river to reservoir:  

In an impoundment made by damming a river, it natural stocks of fishes result from the stocks previously present in the river. Although it is possible to alter the composition of the species stocks later, the initial fishery is most often dependent on natural stocks; only rarely have fish been eliminated from a river system by the use of poisons prior to damming and an effort made to establish from the outset, by intentional stocking, a fish population of the desired species composition. 

Assuming a mixed species population in a river before impoundment, can the contributions of these species to the reservoir population be predicted? The answer is yes, to a limited but continually improving degree of accuracy. The better the knowledge of the ecological requirements of the species, the more accurate can be the prediction. Especially important components of this knowledge, for prediction purposes, are reproductive requirements- for example, the character of spawning grounds and the means for access to them, food and feeding habits, and temperature, oxygen, and current requirements. 

In a riverine fish population on may expect a range of species requirements extending from quiet water to moving water. Thus some species will inevitably be encouraged by impoundment and others discouraged. Similarly, riverine populations are often low in predominantly plankton-feeding fishes, while in a lacustrine situation there is often a very substantial population of plankton feeder. This fact reflects the prevalent difference in available microscopic plant and animal life (plankters) in the two habitats and represents a direction of ecological change that comes with impoundment- change that can be very significant for fish production. In a reservoir made by damming a river, therefore, not all of the newly created habitats may be fully utilized by the expanding populations of native riverine fishes. For example, in Lake Kariba, Zambia, the open water was little used and led to the experimental introduction of a small freshwater herring, Limnotbrissa miodon, from lake Tanganika. Such introductions, of course, may be dramatically successful or catastrophic for the overall fishery. They must be preceded by intensive research. 

Throughout its depth, the temperature of oven a large river is quite uniform although unstable, since it fluctuates with daily changes in air temperature. Upon impoundment, the temperature, except in headwater and surface zones, becomes relatively stabilized and in the depth may change greatly only with the seasons. The change from riverine thermal conditions to those of the impoundment will affect both the abundance and the distribution of the various fish species differently, sometimes predictably.  

In flowing river water there is normally saturation of dissolved oxygen from surface to bottom.  However, at least seasonally in many impoundments, this gas may be in saturated solution only in the surface waters and be so deficient in stagnated depths that fish cannot survive there. Where this occurs, that section of the impoundment must be discounted, at least seasonally, for fish production. Such an adverse effect may be compounded by the development of hydrogen sulphide from organic decomposition in stagnated depths. This gas is injurious to aquatic life and its presence in water can also cause damage to hydroelectric turbines. Since adverse chemical stratification in associated with thermal stratification, it can be partly overcome by the positioning of the water outlets in the dam. 

Possibilities for improvement during construction:  

Advantageous opportunities exist for the improvement of fish habitat and of fishing grounds prior to the first flooding of a man-made lake. It is important to know that some of these improvements can be made only with difficulty or not at all once the reservoir is permanently filled. Only seasonally exposed areas can easily be altered once the reservoir fills. This means that fishery experts should study the possibilities of fish habitat improvement at the earliest planning and feasibility assessment stages of proposed man-made lakes. 

Illustrative of habitat improvement procedures that may be evaluated for applicability is the installation of spawning grounds for preferred species. The application of this procedure requires prior knowledge of substrate spawning requirements and of the greatest extent and depth distribution under water of the suitable substrate. Where it is lacking at the proper depth, desired substrate may sometimes be trucked in or it may be exposed by stripping off an overlay of topsoil. 

Devices that concentrate fish for capture, such as piles of native brush, may be anchored on barren lake bottom. Their location may be marked with buoys that will rise with the flooding water to guide fishermen to the sites and aid navigation among them. Such devices may be particularly useful where barren land is flooded, and may also be valuable for concentrating fish near centres where people are likely to be concentrated and desirous of subsistence or recreational fishing.  

The improvement of fishing grounds has often taken the form of the removal of obstructions, which would limit the efficient operation of likely types of fishing gear. A common means of such improvement has been to remove trees and brush prior to initial flooding in areas of permanent inundation. This derives from the strong resistance to deterioration of wood permanently submerged in fresh water. Loss and damage to gear such as gill nets, long lines, and trawls can certainly be reduced by clearing. Nevertheless, clearing also means that sheltering cover and foraging grounds for fish are removed. Because of these conflicting concerns, clearing proposals require early and individual evaluation for each new impoundment. 

Evaluation must also include recognition that transportation and public health needs are to be taken into consideration at this time.

 Dams as physical barriers to fish movement: 

A river system plays a vital role in the life cycle of migratory species of fish- it is a route up or down which spawners reach their spawning grounds, and fish in their young life history stages reach their feeding grounds. For such species an obstruction like a simple dam can spell doom. For not only may the dam prevent migration upstream, but fish migrating downstream may not survive the effects of passage through the turbines, of, if led into irrigation ditches, they may be stranded and die. 

If a fishery scientist is called in to advise early enough in the planning and feasibility studies on a dam, some unwanted direct effects of the dam as a barrier may be overcome, often at surprisingly low additional cost. In such instances the fishery expert may determine the need, feasibility, and characteristics of appropriate fish-passing devices and fish-guidance structures. Thus, in carefully planned and executed dam systems, uneconomic barriers to migratory fish stocks may be minimized if not completely overcome. 

Among the means of passing fish in both directions over dams and for related guidance systems that may be combined into sound economic investments are: 

-         Fishways;

-         Fishlocks;

-         Fishlifts or elevators;

-         Systems of trapping at the dam and transport around it;

-         Guidance devices for fish to entry of fish passes and traps, or away from danger points such as inlets to irrigation ditches or penstocks.

 The success of any such installation depends on the extent of knowledge of the physiology and behaviour of the species concerned. Often it will be necessary to undertake original and detailed field and laboratory studies, including experiments with models of proposed fish-passing or fish-guidance structures. From this point of view alone it is therefore of extreme importance that fishery experts be involved in the earliest stages of planning for dams across rivers. 

Effects of altered water regime:

 Dams alter water flow characteristics downstream and thus may affect aquatic stocks in many different ways including: water velocity and volume of discharge; water chemistry; temperature, and turbidity; and the stream’s ability to purify its waters. There may also be alterations in the amount of living space for fish, including the extent of spawning, nursery, and feeding grounds. In the estuarine tidal zone a chemical change of potentially vest significance may be effected in salinity, probably in the form of an overall net increase due to reduction of stream discharge. Any reduction in the net annual discharge also lowers the capacity of a stream for self-purification, especially as regards reduction in capacity for oxidation of transported organic material and reduction in the beneficial effects of flushing. 

These effects and changes obviously include elements of danger vis-à-vis the maintenance of aquatic production. For example, reduction in living space means decreased production and the increased vulnerability of fish to predators and fishermen. Wide and sudden fluctuations in daily discharges through dams also reduce potential for aquatic production and place a stress on indigenous species stocks. In extreme situations, the downstream watercourse is alternately wet and dry each day and aquatic production is terminated. A further example occurs when oxygen less water or water laden with noxious substances passing through a dam may eliminate the desired aquatic productivity for some distance downstream. As a specific example of such changes, by 1967 it had already been noted that adverse effects of the still uncompleted high dam on the river Nile near Aswan were manifest in the estuarine fisheries of the delta and were even detectable in the eastern Mediterranean. 

Many potential adverse effects of altered water flow can be offset by careful planning. This planning calls for interaction between engineers and fishery scientists so that any planned flow regulation may involve little or no compromise of the primary objective in creating the reservoir. It may also add significantly to the economic soundness of the whole scheme by eliminating any loss in fishery potential. 

Effects of flooding and siltation:  

A common feature of man-made lakes & reservoir that historic spawning grounds for certain fishes are drowned. These grounds may be the riffles of streams, or quiet, backwater areas of specific depth, bottom and cover types that took a long time to evolve. In either instance the effects may be very damaging to certain species, since successful re-production is of first importance to ultimate yield in a fishery. To a limited degree, the effects of such drowning are identifiable; countermeasures may be justifiable for key species and may be accomplished at least in part by habitat alteration prior to first flooding. Such habitat improvement might take the form of moving earth to provide alternative spawning grounds as the reservoir rises initially and subsequently rises and falls. Water level control during spawning seasons can offset the drowning of spawning grounds and alleviate the possibly even worse effect of the alternate drowning and stranding of nest sites. This is particularly important for such fishes as bass and sunfish of the family Centarchidae, of various species of tilapia, and may kinds of catfish. 

Equally damaging can be smothering of spawning grounds or nests by deposits of silt, where the main stream and tributaries enter impoundments and also in waters adjacent to agriculture land or along windward shores where there is erosion by wave cutting. In order to guard against the potential threat of siltation of aquatic production, early and integrated planning is required of engineers, agriculturists, fishery scientists, and soil conservationists.

 Harmful introduction of exotic species: 

Sometimes the elevation of water levels or the construction of canals to cross natural drainage divides may result in the unwanted spread of certain aquatic plants and animals into areas not native to them. The outcome of such incidental introductions can be serious that fishery, plant protection, and public health scientists should be involved early in any such engineering planning. International introductions of exotic aquatic plants, fishes and other animals should be undertaken only after extensive research.

 Effects of drainage, dredging, and other engineering practices: 

Commonly included among the secondary engineering practices required for reservoir development are drainage, dredging, and modification of stream courses and banks. All of these have some bearing on fisheries and public health. Again, adverse effects can be offset or minimized if engineers, and fishery and public health scientists, are teamed in a common effort along with a resource economist early enough in the planning stage. 

Even though drainage of swamps and marshes, dredging to ensure open channels, and ditching of streams and straightening of their banks may be assets for engineering and public health purpose, they are sometimes also known to be liabilities as regards fishery and wildlife production. Drainage of some swamps may destroy valuable spawning and nursery grounds for fish. Water runoff ditches along roadways may contribute greatly to reservoir siltation problems. Dredging and disposal of the material from the bottom may have the same bed effects as draining. Straightening stream channels may increase fluctuations in stream flow, thereby destroying fish habitats such as the often desirable feature of alternating pools and riffles. It can also accelerate streamside erosion and the depositing of silt in the reservoir.

Effects of pollution:

Fisheries are one of the assets derived from the water of man-made lakes and reservoir that can be destroyed or seriously reduced by pollution- a pollutant being defined as any additive to water that limits usefulness. Forms of pollution that have been found to be damaging to aquatic production include silt, sewage, nutrient inputs from sewage treatment plants and from fertilizers washed in from agricultural land, and toxic chemicals from industry or pesticides. 

Obviously some of these pollutants act indirectly on fishery production through the destruction of habitat, such as silt, which covers food supplies and spawning grounds, and sewage, which has a high oxygen demand and may result in locally destructive oxygen depletions. Also indirect in action are excessive inputs of such nutrients as nitrates and phosphates from sewage plant effluents, or from surface runoff and/or groundwater contributions from farmland. These nutrients may cause over rich blooms of algae, which upon mass die-off, may create local deficiencies in dissolved  oxygen accompanied by fish die-off. The nutrients may also stimulate the growth of higher aquatic plants and increase their hazards for many water uses, such as the generation of hydroelectricity, navigation, fishing, and public health. 

Other pollutants have direct damaging or lethal effects on aquatic organisms. The list of noxious industrial wastes is very long and is continually growing. Included are such things as salts of the heavy metals, acids, alkalis, oils, phenols, detergents, pesticides (especially the commonly used chlorinated hydrocarbons), some kinds of abrasive particulate matter, and even heated water (as from the cooling systems of thermonuclear installations).

Effective multiple use of man-made lakes & reservoirs require that standards of water quality be established for all its uses and that they be enforced by adequate legislation and persistent policing to control pollution. For man-made lakes & reservoir yet to come, the lessons of the past dictate that the necessary steps to protect water quality for all its probable uses be taken at the earliest stage of planning, since both legislation (often a slow process) and costs (often substantial) must be anticipated. All agencies concerned with water quality in the lake and downstream environments should participate in early planning.

 Possibilities for aquaculture: 

The construction of a reservoir for water supply is the classical prelude to the development of a fish cultural enterprise downstream from the dam. Early planning consideration for man-made lakes & reservoirs may advantageously include aquaculture in the overall scheme for water use. One of the economic attractions of aquaculture is that it is essentially a no consumptive use of water, in contrast to irrigation agriculture, which is very highly consumptive. Furthermore, per unit of land, aquaculture yields can under some circumstances far exceed those from agriculture production in terms of economic and protein returns. 

A wide variety of plants and animals may be propagated in small ponds supplied with reservoir water; the variety is so great that market preferences can usually be readily supplied. Such plants include several kinds of watercress, water lettuce, and water chestnut. Among the animals, most popular and productive are different species of fish; shrimp along with other crustaceans and shellfish; frogs, crocodiles, and turtles are also among the prime potential of aquaculture produce. In some circumstances fish can be cultivated simultaneously with rice, the fish being a bonus crop and the rice yield being increased substantially by the presence of the fish. Some irrigation canals are readily adaptable to fish or aquatic plant propagation.

 Although ponds or channels that can be supplied by gravity from a reservoir may be best for aquaculture purpose, the practicability of developing locally intensive forms of aquaculture within the arms of the reservoir basin or on its banks should not be overlooked at the planning stage. In some instances it may be feasible to lift water from the reservoir to supply ponds located above the normal high-water levels.

 Flooding lands for purposes of fish culture should, of course, be permitted only after adequate economic land use studies and the assignment of land and water user priorities. It is also important to remember that, especially in the tropics, ponding water for aquaculture has public health implications, which should be carefully evaluated in advance. 

Experience to date indicates there is little likelihood that ponds for fish culture in the vicinity of reservoirs can ever be justified for purpose of planting native fishes in the reservoir for stock maintenance purposes. If, however, it appears likely that planting an artificially reared fish of a preferred species may compensate for its loss of spawning grounds due to impoundment, a feasibility study might well be undertaken. The introduction should be considered during the planning stage, and also the possibility for establishing facilities for artificial rearing from which owners of small, sometimes domestic; ponds or rice paddies can secure the proper fish of the correct size for stocking their own waters. Among the fish suggested to stock such waters might even be Gambusia, for the control of malaria mosquitoes.       

 Courtesy: Manmade lakes & reservoirs: Planning and development