tailieunhanh - Small-scale freshwater fish farming - Chapter 7,8

7 Selecting the fish species When selecting fish species suitable for farming, various important biological and economic factors need to be considered: 1 market price and demand (not when fish are produced for own consumption) 2 growth rate 3 ability to reproduce in captivity 4 simple culture of the young fish 5 match | 7 Selecting the fish species When selecting fish species suitable for farming various important biological and economic factors need to be considered 1 market price and demand not when fish are produced for own consumption 2 growth rate 3 ability to reproduce in captivity 4 simple culture of the young fish 5 match between available fish feeds and the food preference of the selected fish species It will often be possible to choose from locally occurring species and to avoid the introduction of exotic ones for culture. The most important biological characteristics growth rate reproduction size and age at first maturity feeding habits hardiness and susceptibility to diseases determine the suitability of a species for culture under local conditions. Although certain slow-growing species may be candidates for culture because of their market value it is often difficult to make their culture profitable. It is better that they reach marketable size before they attain maturity thus ensuring that most of the feed is used for muscle growth instead of reproduction. Early maturity on the other hand ensures easier availability of young fish. In fish development the following stages exist 1 egg 2 larva feed on own reserves do not need external food yet 3 fry reserves in yolk sac are depleted external food is now necessary 4 fingerling a young fish older than fry but usually not more than one year old and having the size of a finger 5 juvenile fish not mature yet 6 adult fish ready to reproduce 48 Small-scale freshwater fish farming Baby or young fish are general terms generally referring to the fry or fingerling stage. If you do not intend to breed fish yourself you may have to depend on fingerling supply from the wild. This is generally an unreliable source as the fingerling quantities caught from the wild vary greatly from moment to moment. This is due to the fact that natural fish reproduction depends on unpredictable biological factors water temperature food availability etc.