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Aquaculture Feed and Fertilizer Resources Information System
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Feeding behaviour
Mrigal is mainly illiophagous, feeding on the bottom on decayed vegetation, although it can also switch to a filter feeding mode. The thin terminal lips are adapted for picking up food material from the substratum (Jhingran and Khan, 1979). Larger and more solid food items are masticated by the pharyngeal teeth working against the callous pad on the underside of the posterior pharyngeal roof. Juvenile fish feed intensively throughout the year except between January and March, while adults feed most intensively during the post-spawning period (October to December).
Natural food
After yolk-sac absorption, mrigal larvae and fry start feeding predominantly on zooplankton (nauplii, rotifers, cladocerans and copepods) (Hora and Pillay, 1962). Khan (1972) showed that fingerlings (of up to 100 mm) feed predominantly on zooplankton, while phytoplankton becomes more important in the diet of fish ranging between 100 and 300 mm TL. At around 300 mm TL the fish switch to detritus (Jhingran and Khan, 1979) and in fish above 560 mm TL, semi-decayed organic matter constitutes about 65 to 78 percent of the gut content, while sand and mud make up the rest (Jhingran and Pullin, 1985).
Food items of animal origin are of little importance in adult fish. The most important phytoplankton groups consumed by juvenile mrigal are Chlorophyceae, Myxophyceae, Bacillariophyceae and Euglenophyceae. Natural food fluctuations of different size groups of mrigal are presented in Table 1. |
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