Reservoir Fisheries of India

Inland fisheries

India is blessed with huge and untapped fishery potential. It has 29000 km of rivers, 0.3 million hectares of estuarine, 0.19 million hectares of backwater and lagoons, 3.15 million hectare of reservoirs and 0.2 million hectares of floodplain wetlands and 0.72 hectares of upland lakes. The manmade reservoir resources cover more than 3.0 million ha water spread area and are mostly distributed in varied climatic environment congenial for fish growth. .

There are 14 larger rivers, 44 medium rivers, and innumerable small rivers present in India.

The larger river production of fish has ranged from 0.64 tons to 1.64 tons with an average of 1 ton. However, major landings are being obtained from the reservoirs and floodplain area, which are attained through culture management practices.

The total fish production during 2015-16 (provisional) is at 10.79 million metric tonne (MMT) with a contribution of 7.21 MMT from inland sector and 3.58 MMT from marine sector. Inland fisheries presently has a share of 66.81% in total fish production of the country.

In recent decades, the culture fisheries in inland water bodies has received considerable attention. Within inland fisheries there is a shift from capture fisheries to aquaculture during the last two and a half decade. Freshwater aquaculture with a share of 34 percent in inland fisheries in mid-1980s has increased to about 80 percent in recent years. It has emerged as a major fish producing system in India as a result of initiatives taken by the Government.

Reservoir Fisheries

The reservoirs are classified based on the water spread area and water-holding capacity. The reservoirs are classified into large (>5000 hectares), medium (1001 - 5000 hectare) and small reservoir (<1000 hectare). There are 56 large reservoirs having a water area of 1140268 hectares, 180 medium reservoirs having a water area of 527541 hectares and 19134 small reservoirs having a water area of 1485557 hectares.

A maximum number of small reservoirs are in Tamil Nadu with an area of 315941 hectares (8895 nos.) and is followed by Karnataka (228657 hectares) and Andhra Pradesh (201927 hectares). A larger part of the medium reservoirs are in Andhra Pradesh, Rajasthan and Gujarat. Karnataka has the highest number (12) of the large reservoirs with an area of 179556 followed by Andhra Pradesh which has 7 larger reservoirs with an area of 190151 hectares. About 56% of total reservoir area of the country are distributed in the states of Tamil Nadu, Karnataka, Andhra Pradesh, Kerala, Odisha, and Maharashtra.

(Source: Reservoir Fisheries of India)

Reservoir productivity

The reservoir productivity is influenced by the climatic, morphometric and hydro edaphic features. The geographic location alters the reservoir productivity, nutritional supply and basin characteristics. Among the climate variables, the temperature, rainfall and wind can change the productivity of water bodies. The air and water temperature fluctuation is comparatively lower in southern peninsular than in northern peninsular across different seasons which prevents the thermal stratification. In addition, the rainfall determines the inflow rate of water into the reservoir and this contributes to the water replenishment and nutrient enrichment. The wind helps to maintain even temperature among the entire water body, and normally, this is high during pre monsoon and monsoon seasons.

The morphometry of reservoir is a function of the dam depth and topography of area. The reservoir potential is determined by the depth of the tank. A shallow lake has greater productivity (euphotic zone) due to better mixing of heat and nutrient. A larger reservoir has lower productivity, because the nutrient sinks at the bottom, where organic matter accumulates  and this is not available in the photosynthesis zone.

The Morphoedaphic index used to estimate the potential of the reservoir can be calculated by using the following formula.

Morphoedaphic index = total dissolved solids (mg/l) / mean depth (m).

Physio chemical feature of the Indian reservoirs

In India, majority of the reservoirs fall under low productivity, which has the water quality parameters pH is less than 6.0, alkalinity is less than 40mg/l. The soil parameters such as the pH are less than 6.5, available nitrogen is less than 3.0mg/100g, available nitrogen is less than 25mg/100g and organic carbon is less than 0.5%. The total dissolved solids and specific conductivity directly influence the productivity of the reservoirs.

The soil pH is one of the important parameter, which regulates the productivity of the water bodies. If the pH value is less than 6 then it is a low productivity reservoir, 6.5 - 7.5 is termed medium productivity and more than pH 7.5 is termed a high productivity reservoir.

Fish production from reservoirs

The average fish production potential was estimated at 250 kg/ha of reservoirs.

Reservoir category and state wise production and yield kg ha^-1 is presented in the Table given below. An estimated average fish yield kg ha^-1 is greater in the small reservoir at 49.9 kg/ha, followed by the medium reservoir (12.3 kg ha^-1) and larger reservoir (11.43kg ha^-1). The average reservoir production of the nation is 20 kg ha^-1.

The production of the reservoir is 93650 tons of the potential of the reservoir of 245134 tons. There is scope to increases the fish production by about 50% in the small reservoirs, 16.39% in medium and 22.85 % in larger reservoirs; it means an average total fish potential could increase by about 38%. By stocking of larger size fingerlings and providing formulated feed, an average production of 500kg ha^-1 can be achieved.

Fish production of reservoirs in India

Reservoir potential of the Indian reservoirs

Sources

1. Reservoir Fisheries Resources of India
2. Handbook of Fisheries Statistics