The Union territory of India, Jammu & Kashmir, located Northwards of the Indian subcontinent, is girdled by a number of Himalayan ranges, that route in a west-northwest to east-southeast direction all through the locale. The UT shares its margins with the abutting Indian states of Himachal Pradesh and Punjab on the south and has international borders with Pakistan in the west and China in the east. The stretch is famous far and wide for it′s mesmerizing mountainous serene, refreshing lush greenery, river valleys and numerous aquatic resources ranging from ponds, pools, streams, and wetlands, to the gigantesque lakes and rivers in the plains, and in high altitudes.
The Valley of Kashmir, a lacustrine basin of the inter-mountain indentation joining the Lesser and the Greater Himalayas, is abounded by numerous freshwater lakes (Alam et al. 2015). The region is situated at an average altitude of 1850 m above mean sea level covering an area of about 222236 sq. km extending from 32o 17′ N to 36o 58′ N latitudes and from 73o 26′ E to 80o 30′ E longitudes.
It has a total water spread area of about 32765.3 hectares which constitutes about 2% of its total area (Anon., 2013). The valley is bestowed with diverse aquatic habitats both lentic and lotic, which support a wide variety of indigenous and exotic fish species. The important lakes of the valley include Manasbal lake (fed mainly by groundwater), Wular lake (fed largely by the river Jhelum), Dal lake (fed mostly by freshwater streams), Nigeen and Anchar lake and River Jhelum (Khan et al 2006).
The lakes of the area present an inclination towards altitude, profundity, nutrient levels, as well as proximity to human habitations, and vary from being oligotrophic or mesotrophic to eutrophic.
The Manasbal lake with distinct grandeur and an ′utmost′ jewel of all the valley lakes, is situated at Safapora area of District Ganderbal about 32 Km away towards North-West of Srinagar city, in the Union Territory of Jammu & Kashmir. The word Manasbal is derived from Manusarwar, the sacred lake which skirts the Kailash Mountain along with Gauri-Sar and Rakhas Talav (Kaul,1977; Naik et al., 2015). The lake lies between the latitudes 3414′00.59′′ to 3416′53.45′′N and longitudes 7440′50.22′′ to 7443′ 53.85′′ E at an altitude of 1,584 meters above mean sea level (Babeesh et al., 2019). It is the deepest freshwater lake of the Kashmir valley with a maximum depth of 13m ,covering an area of about 2.81 of which 25 hectares is marshy (Rashid et al., 2013; Lone et al., 2018). The lake is oblong in shape extending North-East to South-West direction with a maximum length of 3.5 Km and width of 1.5 Km ( Rashid et al.,2013).The volume of the water has been approximated as 12.8×106 m3 (Sarah et al., 2011). It is semi drainage, warm monomictic lake, which receives stratification from March till November, followed by mixing in early December making it the only valley lake developing stable summer stratification (Maqbool & Khan, 2013). The lake has no major inflow channels and its water supply is primarily sustained by hefty number of springs spread over its basin and precipitation (rainfall and snow fall)(Shafi et al.,2013). In addition, Laar Kul, a measly irrigation stream on its eastern side, drains water into the catchment from spring to early autumn, which inturn takes of water from the Sindh Nallah (a branch of river Jhelum) irrigating the agricultural fields throughout its course adjoining the lake. (Rashid et al., 2013; Lone et al.,2018). An outflow permanent channel, Nunnyar Nalla, about 1.6 km near Sumbal village drains the excess water from the western side of the lake into the Jhelum River (Jamila et al., 2014).
The manasbal lake serves as an important freshwater reservoir for drinking, recreation, tourism, and other agricultural purposes for the local population (Sarah et al., 2011). The lake is of high economic importance to the area besides providing water for irrigation to Yangoora and Safapora towns (Bhat et al.,2012 The marl lake covers the catchment area of about 22 (Rashid et al.,2013). The landscape of the catchment region is hilly with flat spots at lower elevations (Magray and Jan,2014). The lake is bounded by the Karewas deposits of Plio-Pliestocene age on the northeast and northwestern side below which lies the manasbal village (Babeesh et al. 2017). Close to the northern shore are the ruins of Badshah Bagh, now recognised as Jaroka Bagh, consisting of the remnants of a Mughal fort whilst on the west there is a large marshy tract. On the eastern side are moderately lofty rugged mountains extending upto the mountain, Ahtung in the southeast direction (Ganie et al.,2015). The lake has predominantly a rural ambience with many suburbs namely Gratbal, Kondabal, Jarokbal and Hanji Mohalla adjoining the lake. Out of these, Kondabal and Hanji Mohalla are very important as far as the strength, soundness, and vigour of the lake is concerned (Naik et al., 2015). Kondabal village, (Kond means Kiln and bal means place) situated at the foot of Ahtung mountain along the fringes of the lake, is the site of kilns, quarries, and mines used for limestone deracination and run-off from the hill is accountable for direct and large proportions of Calcium intrusions into the lake (Ganaie et al.,2015; Babeesh et al.,2019).
Hanji Mohalla is inhibited by fishers from which a lot of organic matter and other pollutants enter into the lake (Naik et al., 2015). Besides this, the Laar Kul stream brings in diverse types of terrestrial organic and inorganic matter and other allochthonous material into the lake including major and minor nutrients, polythene, bottles, and other objects (Lone et al.,2018). During current years, the rapid increase in population has ensued the establishment of new human settlements in the catchment belt of the lake. Similarly, the vast stretch of forest converted into agriculture and farmlands, had resulted in opening up the terrestrial ecosystem with heavy loads of nutrients seeping into the lake from the catchment. As a result, excrement and sewer water proceeding from the recent and escalating human settlements, the runoff from fertilized farmland and the residual insecticides and pesticides from the arable lands and orchards plantations has detoriated the quality and bionomics of the lake (Romshoo and Muslim, 2011). The gradual decline in water standard of the lake by contamination in the form of agricultural runoff, domestic effluents, municipal wastes, deforestation and changes in land-use and landcover have reduced the lake volume hastening to eutrophication besides affecting other life forms and lowering of fish stocks (Lone et al.,2018). Currently the manasbal lake is heading towards high eutrophic nature with littoral sites being more polluted and eutrophic than central limnetic sites (Dar et al., 2013; Kanue and Munshi,2014; Gulzar et al.,2015; Tanveer et al.,2018; Gulzar and Abubakr,2019). The absence of a proper sewage treatment plant (STP) is hampering the lake largely.
The Manasbal lake has a good potential resource for capture fisheries and harbours rich biodiversity which forms the life line for the rural economy and environment of the locale (Rashid et al., 2015). A total of twelve species has been reported into the lake among which some economically valued fish species include Schizothorax species (Schizothorax niger, Schizothorax esocinus, Schizothorax curvifrons, Schizothorax plagiostomus), Triplophysa species, Cyprinus carpio vr. communis, Cyprinus carpio var. specularis and Ctenopharyngodon idella. The Schizothorax species contribute about 71% of the total catch in Manasbal lake followed by Exotic carps viz., common carp, grass carp and silver carp contributing about 69% of the total catch of which Cyprinus carpio communis contributed about 45% of total catch and predominated the lake for rest time of the year (Mehraj, 2016).
Common carp, Cyprinus carpio Linneus, 1758), a freshwater cyprinid fish, is extensively disseminated and farmed fish all over the world (Economids, 1991; Kottelat, 1997). This swifty growing robust fish can endure untoward environmental conditions and has been favourably established into the fresh waters all over the world (Golemi et al, 2013). The common carp was brought to India in 1939 from Sri Lanka and then introduced into the Nilgiris. Cyprinus carpio as an exotic fish species, was introduced in Kashmir in 1956, and ever since then, it has invaded almost all types of basins in the valley, eventually becoming a major fishery, especially in the lacustrine waters of Kashmir (Yousuf, 1996 and Bhat et al., 2010). It is locally called as Punjabe gad and occurs in shallow ponds, lakes rich in vegetation, slow moving rivers, and dwells in the middle and lower reaches of rivers, and in confined shallow waters. Regarding reproductive capacity, Cyprinus carpio has been reported to dominate over the endemic fish of valley (Das and Malhotra, 1964). The fish breeds throughout the year in tropical climates with two peak breeding periods; one from January-March and other during July-August. But in temperate areas like Kashmir, winter breeding is not very common, due to the harsh winter when the gonads show inactivity or gonadal diapause (Malhotra, 1966) which remains till February (although gonads are fully mature at the onset of winter). Carps are omnivorous, with a peak affinity regarding the ingestion of benthic organisms such as water insects, benthic invertebrates, insect larvae, worms, molluscs, and zooplankton.