Feeding Preference and Growth Rate of Grass carp (Ctenopharyngodon idella Val.) on 6 Aquatic Plants

The grass carp (Ctenopharyngodon idella) is mainly used for the food production and aquatic weeds control. The aim of this study was to assess the feeding preference of grass carp by 3 submerged plants including curly pondweed (Potamogeton crispus), Eurasian watermilfoil (Myriophyllum spicatum) and coontail (Ceratophyllum demersum), 2 free floating plants including water fern (Azolla filiculoides) and duck weed (Lemna minor) and water silk (Spirogyra sp.). The research was carried out at the Shahid Ansari Fish Reproduction and Breeding Center in 2011. Vegetative organs of experimental plants were collected from the Anzali lagoon and planted in the fish aquaculture. Four weeks later (on 5, May 2011), the grass carp by average weight of 20 g were released in the pools and monthly weighted by the end of experiment. The results showed significant (p<0.001) increase of grass carp weight in the eurasian watermilfoil, duck weed and water silk submerged plants treatments compared to the other treatments. The maximum weight and length of grass carp were observed in duck weed (380 g, 31 cm), eurasian watermilfoil (365 g, 29 cm) and water silk (350 g, 28 cm). The maximum fat percent were also measured on eurasian watermilfoil, water silk and duck weed with 7.21, 7.15 and 7.08%, respectively. Besides the maximum protein content were measured in eurasian watermilfoil, water silk and duck weed treatments with 16.02, 15.88 and 15.68%, respectively