Use of Asian watergrass as feed of grass carp

Abstract

Grass carp (Ctenopharyngodon idella) was cultured in the inundated low-lying coastal wetlands using Asian watergrass (Hygroryza aristata) as feed for 6 months. The study was carried out with three treatments, each with three replications. The grass was planted during plot preparation in treatment one (Grass Planted; GP); the grass was collected those grown in an adjacent land and supplied to the fish in treatment two (Grass Supplied; GS); and the fish were fed with commercial feed in treatment three (Commercial Feed; CF). Similar sized juveniles of grass carp (51 ± 6 g) were stocked at the rate of 12,500 fish ha−1 in each treatment. Important water quality parameters were measured at a monthly interval and found within the suitable range for growth of grass carp. The survival was significantly higher in GP (92.7 ± 1.0 %), followed by GS (90.0 ± 1.7 %) and CF (90.0 ± 2.9 %). The growth parameters (weight gain and specific growth rate; SGR) of fish were found significantly higher in GP, followed by CF and GS. The highest total production was found in GP (6770 ± 424 kg ha−1), followed by CF (6733 ± 536 kg ha−1) and GS (5519 ± 483 kg ha−1). The highest net economic benefit and benefit-cost ratio were found in GP (US$ 13375.50 ha−1 and 3.32) and the lowest in CF (US$ 4958.25 ha−1 and 0.42). The results of the present study indicate that Asian watergrass can successfully be used in commercial culture of grass carp and it may significantly reduce the production cost.