Factors Affecting Fish Production

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Delince (1992) emphasized that the factors which significantly influence fish production, act within a network of interactions. The three main factors are; availability of food (ad libitum), dissolved oxygen and the ammonia concentration of water. Our studies also reported that low fish production coincides with high BOD, high ammonia and low DO. Cuenco et al. (1985) study of environmental factors affecting the population growth of American catfish, showed that, besides available food and oxygen, non-ionized ammonia in the water is also an important factor.
The natural food of the studies fishes have been determined by several works by examining the gut contents (Kumar et al., 2007; Kumar and Chakarbarti, 1998; Chakarbarti, 1998; Jhingran,
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Fish are quite specific in the digestion capability of different groups of food. It is necessary to understand the relationship between the type of food consumed and the quality and quantity of enzymes produced in the alimentary tract. It was observed that specific cellulase and amylase activities were higher in Catla catla which also advocate the phytoplanktivorous feeding habit of this fish species. It was further observed that these activities are higher in managed ponds in comparison to unmanaged ponds. Sarbahi (1951), Dhage (1968) and Philips (1969) suggested that amylase activity in the intestine of herbivores carps is more intensive than the carnivorous fishes. Bairagi (2002) reported the presence of amylolytic bacteria (responsible for exogenous amylase production) from the gut of Catla catla even after 24 hours of…show more content…
Digestion depends on the physical state of food, as well as the kind and quantity of enzymes secreted. It is reported that in addition to endogenous digestive enzymes (Dhage, 1968; Kawai and Ikeda, 1972 and Das and Triphati, 1991) there is distinct microbial source of digestive enzymes in fish gastrointestinal tracts (Bairagi et al., 2002, Lindsay and Harris, 1980; and Lesel et al., 1986). These microbial populations grow depending upon the food taken in by the animal, digestive secretions and fragments scaled off the mucosal epithelium (Lasel, 1991; Saha and Ray, 1998 and Bhatnagar and Khandelwal, 2009). Fish take in a large amount of bacteria into their gut from their aquatic environment and some of these microbes colonize the gut of the fishes forming persistent populations adhering to intestinal mucosa and assisting in the production of intestinal enzymes as an exogenous source. It can be said that environmental conditions play an important role in the formation of gut adherent microbial populations and the type and amount of enzyme production. This could be the reason for differences in the amount of enzymes from the fish guts in unmanaged and managed

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