Mrigal - Feeding methods

Feeding methods in carp polyculture depend on the life history stage of the fish (nursery, fingerling rearing or production), the size of the pond, availability and the cost of labour. Broadcasting or hand feeding is the most common form of feeding in semi-intensive culture practices. In nursery ponds carp larvae (7-8 mm/1.4 mg) are generally fed a mixture of rice bran/rice polish and mustard oil cake/groundnut oil cake in 1:1 ratio in finely powdered form for 15 days to produce fry of 15-25 mm in length and 300 mg in weight. During the fingerling rearing phase, fry are reared for 2-3 months to fingerlings of 80-100 mm in length and 5-10 g in weight.  During this phase, the fish are fed with an almost identical feed as during the nursery phase. In the first month, they are fed by broadcasting the feed either in powdered or granular form over the pond surface. During the second and third month, 50% of the required feed is broadcasted and the remaining 50% is provided in the form of moist dough balls (Figure 7) that are placed either in bamboo baskets or in trays suspended from long bamboo poles from the side of the pond (Figure 6). The trays are placed at three levels in the water column for easy access by the various carp species that feed at different depths. During the grow-out phase for the production of table-size fish as well as for broodstock conditioning, a similar 3-tier feeding system in bamboo baskets/trays is used. The feeding baskets/trays are checked daily in the afternoon for any left over feed, whereupon the amount of feed is adjusted accordingly on the following day in order to avoid feed wastage and deterioration of water quality (Nandeesha, 1993; Mukhopadhyay and Chattopadhyay, 2002).   Miaje et al. (1999) demonstrated that pelleted and dough balls, comprised of mustard oil cake and  rice bran, appear to be more suitable than powdered feed for Indian major carps and Java barb in polyculture.

Alternatively the fish are fed on a dry 7:3 mixture of uncooked defatted rice bran and oil cakes (Figure 8), suspended in perforated polyethylene bags on poles (Figure 9) at various locations in the pond (Figure 10). About 20 to 25 feed bag poles are deployed per hectare. Fish browse on the feed through the perforations and within 2-3 hours most of the feed in the bag is utilized. This method results in minimum wastage of feed and allows for easy application of medication (Veerina et al., 1993). The use of pendulum demand feeders is presently being investigated (Sengupta et al., 2004).