We know which beings live in this water. We fulfill our need for protein by eating these beings. We call them fish. So to cultivate fish in water, we have to know something about it. We know, we need houses and good environment for our living; and also fishes need good environment for living. Let us discuss the quality of water and its impact on fish culture. Physical properties of water and their influence on fish culture : The productive capacity of a pond can be assumed by observing the physical condition of water in it. The physical properties of water in fish culture is discussed below: (1) Water colour : Light green coloured water indicates more productivity of a pond. Water colour is different because of different types of organic and inorganic materials. Productive capacity may be assumed by seeing the water colour. It should be understood that there is natural food for fish in water if the water is green or brown green. The colour of water can be maintained by applying fertilizer regularly into the pond.
(2) Clearness of water : The productive capacity of a pond is more when the clearness of water is upto 25 cm or below. Besides, it is undrstood that there is not enough food for fish if the palm can be seen when a hand is submerged up to elbow. So fertilizer should be applied in the pond. (3) Depth of water : Depth of water is an important element for fish culture. For fish culture
Figure : Test of Natural foods the depth of water of a pond ranges between 1.5-3 metre. So 2 meter depth is best for fish culture. Sunlight cannot reach in the deep water, if water depth is too much. Moreover, the water may warm up if the water depth is too short. (4) Water temperature : The growth of fish also depends on the temperature of water. Growth of fish is less during winter and more in summer. For Rui (carp) culture the best temperature range is 25°C-30°C.
(5) Sunlight : Food production depends on —- sunlight. So, high trees on the bank of the pond should be cut for entrance of sunlight profusely
ater. The floating water hyacinth, dhe algae and weeds create obstruction to enter 313 the sunlight into the water.
Chemicals properties of water and their influence on fish culture : Some chemical properties of water for fish culture are Figure : Sunlight in the pond discussed. (1) Dissolved Oxygen : Oxygen released by aquatic plants is dissolved in water. Some amount of oxygen from air is also mixed with water. The fish in the pond, aquatic plants, animals respire with the help of this oxygen. For lack of oxygen, fishes unitedly float on the water. It is called gasp of fish. Causes of decreasing oxygen in the water : (1) Decomposition of leaves and branches of plants. (2) Use of excess raw cow dung (3) Cloudy sky (4) Water being too muddy. Recovering oxygen deficiency: Defficiency of oxygen in water can be recovered instantly by creating waves on the water sunface. Waves can be created by swimming or stirring the water using bamboo. (2) Dissolved carbon-dioxide : If the amount of carbon-dioxide is increased in a
the water somehow, poisoning occurs. If the bottom of the pond contains too much organic matter and mud, there will be excess of gas due to high temperature. (3) Water p : Whether the water is acidic or alkali can be determined by po metre. If p’ value is less than 7, it is acidic water, if more than 7, it is alkaline and if 7 it is neutral. Relatively alkaline water is good for fish culture. So the water p” 6.5-8.5 is helpful to grow natural food in a pond. (4) Phosphorus : Phosphorus increases the amount of fish food in water (5) Nitrogen : Nitrogen is very beneficial to aquatic micro-organism. This micro-organism is the principal food for fish. (6) Potassium : There is need to apply potas in the water to fulfill the demand of food for fishes. We came to know from the above discussion that water is necessary for fish culture. Fish production in a water body depends on the properties of water.
Task: Discuss in groups and present the impact of water quality on fish culture
Lesson 7 : Water for livestock Water is called life. Without water man, animal-birds and plants cannot live. Water is essential to the translocation of nutrient elements from one place to another in the body. It is necessary for digestion, metabolic activities and to emit polluted matter from the body. Water has a role to control body temperature. Water is an essential element for living bodies. Water is maximum among the body building elements. The amount of water is the animal body is about 70%. A domestic animal and a domestic bird are drinking water Sources of drinking water for domestic animals and birds : Clean and pure
water from a tube well, pacca dug well, pond, etc. son Functions of water in the bodies of animals and birds : Water helps to
(1) absorb food, (2) control body temperature and digest food,
(3) transmit nutrients to the cell, ( 4) maintain body fluidity and ( 5) transport different types of enzymes. Water deficiency problems of domestic animals and birds : There will be obstacle to taking other foods if sufficient amount of water is not taken. The production of animal and birds, and their weight will decrease. The birth of a baby or laying of egges may face danger from water deficiency during pregnancy of domestic animals and birds. They may die even due to shortage of water. Solution : Cattle need to drink plenty of clean and pure water. Take special care so that animals and birds cannot drink polluted water. Water should be sterilized. Besides this, the necessity of water for animals and birds depends on food, weather and age. Water is more needed in summer than in winter. Water requires more if dry grass and granular feed are taken more. Water requirement: Water is more essential for milking cows.
A milking cow daily drinks 30-40 litres of water. A hen drinks water double of its food taken.

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