Impact of Exotic Carps in the Polyculture with Indigenous Carps: Competition for Food
The fingerlings of indigenous carps such as catla (Catla
catla), rohu (Labeo rohita) and mrigal (Cirrhinus mrigala)
with exotic carps such as silver carp (Hypophthalmichthys molitrix),
bighead carp (Aristichthys nobilis) and mirror carp (Cyprinus carpio)
were cultured together in a fish pond at Bangladesh Agricultural University,
Mymensingh, in order to determine the food electivity, dietary overlap and food
competition among indigenous major carps and exotic carps. Phytoplankton (Chlorophyceae,
Cyanophyceae), zooplankton (rotifers) were the dominant groups in the cultured
pond. Chlorophyceae was dominant in the diet of rohu. Chlorophyceae and rotifers
were the preferred food of catla. Mrigal preferred phytoplankton than zooplankton.
Rohu showed positive electivity for zooplankton. Silver carp consumed large
quantity of phytoplankton and also preferred rotifers. Chlorophyceae was the
dominant food group in the diet of bighead. Mirror carp also preferred plant
food organisms dominated by Chlorophyceae. Bighead had positive trends towards
phytoplankton. Both mrigal and mirror carp had positive electivity towards phytoplankton.
The higher level of dietary overlap occurred between rohu and silver carp followed
by between rohu and bighead carp and between catla and silver carp. The lowest
level of dietary overlaps occurred between rohu and mirror carp.
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