In West Bengal, especially in the southern districts, aquaculture is dominated by prawn culture. So during the three months of culture period, from March to June 2006, the water quality was monitored in ten shrimp ponds distributed in 10 different zones. To analyze the present status, Aquatic Health Index (AHI) was evaluated by using the data of the selected ponds. The lower value of the index reflects the deteriorated condition of the culture ponds due to poor quality of source water, whereas the congenial environment for shrimp culture is indicated by higher index values. The lower value of AHI at Stn 1, Stn 8, Stn 5 and Stn 2 may be attributed to the proximity of these stations to Kulti lock gate, which receives huge quantum of untreated sewage and wastewater from the city of Kolkata. Stn 10, Stn 9 and Stn 6 offer a favorable water quality environment for shrimp culture being far away from the city and situated within mangrove-dominated Indian Sundarbans. Moreover, the use of the formulated feed in these ponds has upgraded the water quality parameters of the ponds, which has been reflected through higher AHI values.

India has great potential for making use of the marine and estuarine resources for economic benefit. In the maritime state of West Bengal, in the south, numerous river openings like Harinbhanga, Gosaba, Matla, Thakuran, Saptamukhi, Muriganga and Hooghly have encompassed about 108 islands crisscrossed and intersected by various creeks and inlets before ending up at the Bay of Bengal. In West Bengal, the three major districts, namely, 24 Parganas (N), 24 Parganas (S) and Midnapore, account for 10,055 sq km of coastal area. 24 Parganas (N) and 24 Parganas (S) have an estimated brackish water area of 1,80,000 ha, which exhibits a production of 19,960 m from a culture area of 45,000 ha. The quality of prawns from this area has recently deteriorated in terms of microbial load and heavy metal load and suffered burst in the late 1990s due to several negative reasons related to environment and has been banned by the European Union on the export quality criteria. However, the magnitude of alteration of environment in relation to shrimp culture has not been quantified for this state, except the fish juvenile loss due to wild harvest of tiger prawns from the coastal waters (Sastry and Miller, 1981; UNEP, 1982; Mitra et al., 1994; and Mitra and Choudhury, 1995). Regular monitoring of the entire process is of utmost importance in this context to keep an eye on the quality of aquatic phase in and around the shrimp culture farms. One important step towards this is scaling the water quality of the marine and estuarine compartment through consideration of relevant parameters, which are functions of space and time. The primary objective of scaling is to develop an index through which a single value can be assigned to the aquatic phase for the purpose of its scoring in terms of status, use and management (Fast and Menasveta, 2000). Thus water quality indices aim at giving a single value to a particular aquatic system on the basis of the list of constituents (parameters/variables) and their concentrations in the said aquatic system. One can then compare different samples for quality on the basis of the index value of each sample (Shannon and Weaner, 1949). The present paper is an approach to compare the water quality of 10 shrimp ponds distributed in 10 different zones in and around Indian Sundarbans, with the aim to prepare a scorecard for rating these water bodies in connection with the culture of tiger prawn, Penaeus monodon. Culture of the tiger prawn at the wrong sites has led to adverse impact on the growth of this cultured species. Several farms located at the outskirts of the city of Kolkata receive wastes of complicated characters along with organic load through DWF and SWF canals, that deteriorate the water quality of the culture pond to a great extent. This leads to poor growth, disease susceptibility and low flesh quality of the cultured species. It is at this point the importance of evaluating the culture condition arises, which has been highlighted in this paper through Aquatic Health Index (AHI). The index is basically a modified form of Brown's or the National Sanitation Foundation's water quality index (1970)

Life Sciences Journal, Shrimp Culture Ponds, Indian Sundarbans, Aquatic Health Index, Shrimp Culture Farms, Hydrological Parameters, Argentometric Method, Congenial Environment, Anthropogenic Stress, Aquaculture Authority, Pollution Control Authority.