Production of fish is very important (Tripathi and Harsh, 2002) because major source of protein all over the world is fish and 60% of people depend on protein intake for healthy life (Osibone et al., 2009). Twenty-six percent meat is obtained from fish, which is insufficient to fulfil the protein requirement of rapidly growing population, so there is a need to increase the fish production exploiting all the aquatic resources in Asia (Delgado et al., 2002; Louka et al., 2004). Fish meat is good for health, recommended by doctors in various diseases like cardiovascular ailments, diabetes, depression, stroke, hypertension and rheumatoid arthritis (Karanth et al., 2009; Hussain et al., 2011; Jabeen and Chaudhry, 2011). Coronary heart disease is the central reason of death in several parts of the world including Pakistan and seen less in people ingesting more fish (Hassan et al., 2010; Afkhami et al., 2011).
According to the Food and Agricultural Organization (FAO) statistics, global fisheries products consumption have been increased by many folds at the start of this century although decline in capture fisheries and aquaculture production reported by many researchers due to aquatic pollution. Overtime since 2000, aquaculture production increased from 35 to 50 million mt in 2005. While over the same period, capture fisheries were constant about 94 million mt. It is obvious that if demand of fisheries products continues to increase, it should be necessary to be met by using aquaculture (FAO, 2007).
Demand of freshwater for agricultural, industrial and domestic purposes have been increased due to population explosion, which is a serious threat for aquaculture and fisheries. Salinization of secondary level in many arid and semi-arid areas around the world is significant environmental problem, affecting up to 380 million hectares of soil, including 100 million hectares of cultivable land (Ghassemi et al., 1995; Lambers, 2003). Industrial revolution results the dumping of many toxicants in the water reservoirs that changing the salinity level continually, which provide stress for the exposed wild fish (Lotan, 1960; Winger and Lasier, 1994). Freshwater fish is threatened group of vertebrates as more than 5000 species have assessed by IUCN in this regard with major threats of habitat change, overfishing, invasive species, environmental change and pollution (Reid et al., 2013). All of these circumstances are creating demand for brackish water aquaculture for handling the alarming changing situation (Anyanwu et al., 2007; Akinrotimi et al., 2011).
Inland saline and brackish water aquaculture is economically profitable and ecologically adaptive technique in neglected and remote areas due to under-estimation of the worth of local resources i.e., barren land and underground saline and brackish water which is unfit for agriculture and drinking. It is one of the cost-effective option for use of more than one billion hectares of abandoned salt affected land and underlain brackish water resources all over the world. Apart from marine fisheries, it is important source of cheaper fish protein with 96% biological value and 3.55 protein efficiency ratio (Chughtai and Mahmood, 2012). It helped to reduce or eradicate the epidemic diseases in fish. Moreover, incidence of diseases taking place in freshwater can abridged by enhancing salinity (Altinok and Grizzle, 2001). Arid and semi-arid salt-affected land is considerably freehold and inexpensive than other (Doupé et al., 2003). These extra advantages create attention towards brackish water aquaculture.
Major carps like Catla catla, Labeo rohita and Cirrhinus mrigala are prominent species of South Asia and famous for fish farmers in pond culture system adding over 1.8 million tonnes of fish production (Chaudhuri et al., 1974; FAO, 2003). Pakistan have vast water resources including brackish, fresh and marine water, where merely carp culture is under practice in earthen ponds using extensive farming method with little input. Fish fauna is rich in Pakistan but only nine of the species including seven warm water and two cold-water species are under culture on commercial level (FAO, 2008). Much of the area is affected by the waterlogging and salinity changing groundwater into brackish water where fish culturing can help restoration and desalinization of the soil (Mateen et al., 2004). Less amount of information is present about the fish’s growth in brackish water of Pakistan. Lack of freshwater with issue of enhancing salinity is present in southern Punjab where freshwater fish culturing is difficult task (Davidson, 2000).
In Southern Punjab, Cholistan is one of the largest deserts of Pakistan comprised of Bahawalnagar, Bahawalpur and Rahim Yar Khan covering 66,55,360 acres; out of which largest part is in Bahawalpur region: 40,28,217 acres. It consist of sand dune, sandy soil, loamy soil and saline-sodic clayey soil. Groundwater is mostly saline and unfit for human and livestock consumption (Kahlown, 2007). Local people are nomadic and livestock is only source of their living. Shortage of water, continuous overgrazing and shrubs and tree’s cutting have caused threats to livestock. So brackish water aquaculture is only best option to be executed here to support life in harsh climate by using local natural resources (underground brackish water and barren land).
In marine or brackish coastal waters, over half of the aquaculture production is taking place worldwide. Inland culture of euryhaline species is under practice in Australia, China, Ecuador, Thailand, India, United states etc. Shrimp (Peneaus monodon), Barramundi fish (Lates calcifer), Red tilapia (Orechromis mossambicus) and gilthead seabream (Sparus aurata) are some of the species being reared in inland brackish conditions (Partridge et al., 2008). Brackish water aquaculture play a key role in the periodic supply and accessibility of fish for improved food supply and jobs for youth and women in the coastal regions of Nigeria (Anyanwu et al., 2007; Klennert, 2009; Akinrotimi, 2011). In Iran, trout farming is under practice for development of inland aquaculture (Alizadeh et al., 2016). In Malaysia, brackish water farming was supplying increased demand of fish to growing human population so acting as one of rapidly growing part of economy in last decade (Ramzani et al., 2013). Use of GIS, distant recognition and GPS approaches are helpful in site selection for brackish water aquaculture (Gupta, 1995; Ramesh and Rajkumar, 1996).
Brackish water has a salty, unpleasant taste and higher salinity (500–17,000 mg/l) as compared to fresh water while not saline as seawater (30,000–40,000 mg/l) (NGWA, 2010; WHO, 2011). Salinity level, TDS and conductivity of water used mainly for classification of water. Freshwater have conductivity: 150-500µs/cm, TDS: <1000 mg/l and salinity: <500 mg/l. While brackish water have: conductivity: 1000-80,000 µs/cm, TDS: 1000-5000 mg/l, salinity: 500-17,000 mg/l and seawater have conductivity: 55,000 µs/cm, TDS: 30,000-40,000 mg/l, salinity: 35,000-40,000 mg/l (Malmberg, 1965; NGWA, 2010; Rusydi, 2018; Jonsson et al., 2013; Sharma et al., 2017). Brackish water is mainly present in estuaries where seawater and freshwater were mixed (Liu and Liu, 2014). Formation of brackish water can also be result by the industrial effluents having dissolved salts, saline soil’s leachates, salt deposits runoff (Joshi et al., 2006; Morillo et al., 2014; Cucci et al., 2016;) and groundwater connection with evaporating creations or mixing with deep aquifers of highly mineralized condition (Zuurbier and Stuyfzand, 2017; Xing et al., 2018). Yet principal causative source of brackish surface water is the saline water mixing (from the open wells) with fresh water (Clayton et al., 2014).
Water quality parameters are necessary to observe for any aquatic experimentation (APHA, 1998). At optimum level of physicochemical factors, highest amount of fish can be obtained (Sinha and Srivastava 1991). Food, season, temperature, space, salinity, size, age, feeding habit, water quality, food supply, management practices and physical activity are factors influencing the growth of fish (Sargent, 1997; Imsland et al., 2001; Jankowska et al., 2007; Weisberg et al., 2010). As fish are poikilothermic and remain submerged in water on permanent basis, so directly influenced by alteration in surroundings. Alteration in number and magnitude of fish represent its growth (Weatherly and Gill, 1987). Quantity of available energy for growth of fish altered by the salinity level due to change in the ionic and osmotic regulation’s energetic cost (Iwama, 1996). Amount of dissolved salts in water body refers to the salinity (Boyd and Tucker 1998; Yan et al., 2015). Dissolved salts comprise of potassium nitrates, magnesium sulphates, sodium bicarbonate and sodium chloride (NGWA, 2010). Inorganic matter like minerals, metals, salts and dissolved organic compounds within water are included in total dissolved solids (TDS) (Sharma et al., 2017). Measure of the amount of ions that have ability to carry electrical current is electrical conductivity (WHO, 2011). Conductivity of water measured to evaluate the salinity level and TDS of water. Possible biological value of water estimated by the oxygen level. Poor quantity of dissolved oxygen have influence over metabolism and biochemical configuration of tissues of fish (Parry, 1966). While pH and temperature is determination factor for biological actions (Huet, 1986, Shepherd and Bromage, 1992). Water temperature have inverse relationship with dissolved oxygen (Boyd 1981). All of these physicochemical parameters are necessary to evaluate in aquaculture. Current study is planned to observe the effects of various physicochemical parameters of brackish water.