5.0 FEEDING OF HATCHLINGS AND FRY

Lakshmanan, (1969) from India discussed the 'problems of feeding, hatchlings and fry: His findings are as follows: One of the important factors governing survival and growth of hatchlings and fry is the availability of proper food. In the majority of the fresh-water species (Schaeperclaus, (1933); Alikunhi (1952), (1958); Hora and Pillay (1962), the hatchlings of all cultivated carps commence feeding after they assume the horizontal swimming position. Initial feeding from environment commences even before the completion of yolk absorption at a stage when the mouth parts of the hatchlings are under-developed and the motile capabilities are limited. This compels the hatchlings to hunt for food items which are microscopic and relatively slow moving. The stage of yolk absorption and commencement of feeding from the environment is the most critical period for want of the proper type of food in sufficient quantities (Alikunhi, 1958).

As far as nursery pond treatments are concerned, green and organic manures appear more suitable for the production of food for hatchlings and fry. The higher economy of organic fertilization could be justified by the better returns in terms of high survival rates and healthy growth of fry. However, in relation to the problem of feeding hatchlings and fry of fish, the need is to evolve techniques for the sustained production of selected items of plankters under controlled conditions.

Growing of fry, exclusively on additional feed is extremely difficult though not impossible (Kuronuma 1968). According to Schaeperclaus, at least 50% of the food must be composed of natural feed ingredients. Hence in the practice of rearing hatchlings and fry in concrete tanks, cemented or brick-lined nursery ponds, feeding with zooplankters collected from other sources is a necessity in order to get satisfactory results in survival and growth. It is established that the growth under additional feeds is poorer than that under natural diet and that the growth with a mixture of natural feed and conventional feed is better than that of natural feed alone. According to Tal and Hepher (1967), a balanced diet formulated with due consideration of the natural feed in the ponds may bring good returns in carp yield.

Feeds of plant and animal origin are many. Some of the important and commonly used supplementary feed ingredients for hatchlings/fry are presented in Table 8.

Table 8: Supplementary feed ingredients

Source: Lakshmanan, 1969

Jeyachandran and Raj (1976) made experiments with additional feeds on Cyprinus carpio fingerlings. Results of the feeding experiments, growth measurement, proximate composition of different feeds used and protein and fat content of fish fed with different feeds at the end of the experiment (dry basis) are given in Tables 9–12.

Table 9 : Experimental results of the feeding experiments

Table 10 : Growth measurement

Table 11 : Proximate composition of different feeds used

Source: Jeyachandran and Raj, 1976.

Table 12 : Protein and fat content of fish fed with different feeds at the end of the experiment (dry basis)

Conclusions have been derived as under: The results of the chemical analysis for protein and fat of the fish fed with the different feeds are compared with protein and fat present in the different feeds. It is observed that there is a negative correlation between the protein in the feed and the protein in the fish (r=0.23), that is to say, when the protein in the feed increases, the protein in the fish decreases. A positive correlation was found between the fat content of the feed and the fat in the fish (r=0.76) indicating that as the fat in the feed increases, the fat in the fish also increases.

Comprehensive nutritional studies related to vitamin and miner. l requirements were reported by Ketola (1976) The requirements for various fish species are given in Table 13.

Table. 13 : Summary of minimum dietary requirements of fishes

¹ initial body weight in grams;
² also growth;
³ estimated from date.,
Source: Ketola, 1976.