Fisheries And Aquaculture

FISHERIES AND AQUACULTURE

Fishes are rich in protein, vitamins and mineral salts and are also known as valuable protective food. Fish forms an important item of the diet in many areas of the world. The development of fisheries is therefore, one of the most promising industry.
India has a coastline of about 8,129 km, 5 million km of continental shelf and 2.02 million of exclusive economic zone. India is a major marine fish producer and ranks seventh in the world
Areas where fish are reared commercially, are known as artificial fisheries.
The fishes are bred, reared and later harvested. The fishery may be a natural water body or an artificial one. A variety of fish may be reared together.
In addition to fish, aquatic crustaceans and molluscs are included in fisheries. In India the economically most important crustacean fisheries are those of prawns, shrimps and crabs. Among molluscs, edible oysters and pearl oysters are also of economic importance.

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AQUACULTURE AS AN OCCUPATION

Aquaculture is an occupation of many living near rivers and the sea and most aquaculture jobs are located in coastal community. Aquaculture involves the rearing and management of useful aquatic plant and animal resources such as fish and shell fish, (prawn, molluscs, crabs etc.) It is also known as fish farming and accounts for about ten percent of the world’s commercial fish harvest. China leads all countries in aquaculture production.

Fish farms range from simple ponds or flooded rice fields to highly engineered hatcheries in which the environment is monitored and kept under control. Environment control eliminates harmful environmental conditions and helps fish flourish and grow fast. Fish are provided with proper nutrients as per a regulated plan and are protected from the harmful animals that prey on them. Aquaculture is utilised for culturing pearls on a commercial scale as well as in:

i. Rebuilding of salmon and trout stocks that have been severely reduced, and

ii. Raising fishes for consumption as food such as carp, cat fish, gourami, milk fish, salmon, tilapia etc..
Practice of aquaculture also includes Pisciculture and Pond culture (fish cultivation in large water bodies).

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 Pisciculture (Fish Farming)

Is concerned with the production of fish in lakes, rivers, large ponds, canals and is called fresh water or inland fisheries. In Pisciculture young fishes are reared in nursery ponds, transferred to lakes or rivers and finally harvested as fish for table food.

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 Pond culture (Kitchen Fisheries)

This involves culturing fish in small ponds. This practice is quite common in Bengal. Proper management is carried on till fish attains full size. They are also protected from diseases.

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EFFECT OF CHANGING ENVIRONMENT ON AQUACULTURE

Fish population is adversely affected by a number of environmental factors. These are as follows

 Water Pollution

The problem of water pollution mainly affects marine water fish. A variety of insecticides, pesticides, industrial effluents and domestic sewage find their way into many rivers and pose a serious problem for fisheries. The magnitude of pollution varies with the size of the river, the flow of water etc. Let us take few examples.

o The paper mills located on the bank of a river in Orissa consume nearly 270 million litres of water per day. This heavy withdrawal of water together with the discharge of high toxic effluents causes considerable harm to the fisheries for a stretch of nearly 24 km downstream.

o The effluents from Sindhri fertilizer factory have been found to have adverse effects on fish and prawn. Vast investigations in respect of effluents of paper pulp-textile industries, tannery manufacturing units, sugar distillery, coal, etc. have shown adverse effects on fisheries while sewage used as a fertilizer for fish farm has been found to cause extreme damage to fish culture.

o Thermal pollution caused by the discharge of hot water used for cooling reactors and generators can be a serious problem in tropical waters where the normal temperature itself is high and further increase would be lethal to the fish which are already living in the higher ranges of temperature tolerance.At present, a potential source of pollution is the atomic reactor wastes. Consequences of water pollution are given below.

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Many of favourite fishes like the Bombay Duck have almost disappeared from the Kalu river near Mumbai. This has been due to the release of a number of toxic wastes from the chemical industries into the river.

Excessive use of chemical fertilisers may lead to the phenomenon of Eutrophication (enrichment of the water body with nutrients). This results in algal bloom, (excessive growth of algae which use up available oxygen) followed by oxygen depletion in water and ultimately the death of fish.

Thermal (heat) pollution from various heavy industries causes fish mortality.

Utra violet radiations affect fish eggs that become non-viable, that is, they fail to develop.

Leakage of petroleum from ships and off-shore oil wells forms an oil slick on the surface of the water and thus fishes are unable to breathe due to nonavailability of dissolved Oxygen in the water.

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Fishing boats in India

World Fisheries Day

Integrated pig- fish farming

Farming of fishes in cages

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