Individual study: Preferences of grass carp for macrophytes in Iberian drainage channels
Catarino L., Ferreira M. & Moreira I. (1997) Preferences of grass carp for macrophytes in Iberian drainage channels. Journal of Aquatic Plant Management, 35, 79-83
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Parrot’s feather: Biological control using herbivores
A replicated, controlled, laboratory study from 1994 to 1996 in Portugal (Catarino et al. 1997) found that grass carp Ctenopharyngodon idella did not reduce the biomass or cover of parrot’s feather Myriophyllum aquaticum. Biomass and cover of parrot’s feather did not differ between ponds where grass carp were present (biomass: 0.09 kg/m2, cover: 5%) and ponds where carp were not present (0.09 kg/m2 and 5%, respectively). Grass carp favoured soft-tissue native plants relative to parrot’s feather. When presented only with parrot’s feather and water hyacinth Eichhornia crassipes, one year old grass carp consumed parrot’s feather at a daily rate of approximately 3% of their body weight but this increased to 20% by the age of two. Trials were conducted in six 660 l plastic tanks. Five tanks were stocked with carp and one control tank had no carp. Grass carp were presented with a selection of four plants with a total fresh weight similar to the biomass of fish present in the tank. After two days, the biomass of each plant species was weighed. The number of grass carp per tank was not specified.
(Summarised by Ricardo Rocha)