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Answer:
10 FISH FEEDS AND FEEDING
10.0 Introduction
1. In Section 2.0 of this manual, you have learned that plants are able, through photosynthesis, to utilize sunlight and simple nutrients to produce new organic material. On the contrary, animals, including fish, cannot. Thus to survive, grow and reproduce, fish need to feed on organic materials such as plants, other animals, or prepared feeds containing plant and/or animal material. It is therefore most important for you to ensure that your fish get the food they require, both in quality and in quantity.
Selecting fish foods
2. There are three types of food used in fish ponds:
natural food;
supplementary feeds;
complete feeds.
3. Natural food is found naturally in the pond. It may include detritus*, bacteria*, plankton*, worms, insects, snails, aquatic plants and fish. Their abundance greatly depends on water quality. Liming (see Chapter 5) and fertilization (Chapter 6), in particular organic fertilization, can help you to provide a good supply of natural food to your fish.
4. Supplementary feeds are feeds regularly distributed to the fish in the pond. They usually consist of cheap materials locally available such as terrestrial plants, kitchen wastes or agricultural by-products.
5. Complete feeds may also be regularly distributed. They are made from a mixture of carefully selected ingredients to provide all the nutrients necessary for the fish to grow well. They must be made in a form which the fish find easy to eat and digest. These feeds are quite difficult to make on the farm and are usually quite expensive to buy.
6. The system of production can be defined according to the type of food given to the fish:
extensive: fish production depends entirely on natural food;
semi-intensive: fish production depends on both natural food and supplementary feed; more fish may be reared in the pond;
intensive: fish production depends entirely on complete feed, and the stocking rate no longer depends on food availability but on other factors such as water quality.
7. In the following sections, you will learn more about natural food (Section 10.1) and supplementary feeds (Sections 10.2 to 10.6). If you are interested in complete feeds, you should read another FAO manual entitled Feed and feeding of fish and shrimp: a manual on the preparation and presentation of compound feeds for shrimp and fish in aquaculture, by M.B. New (Rome, FAO, ADCP Report 87/26, 275 pp., 1987).