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.

Keywords

• Coastal wetlands
• Aquaculture
• Hygroryza aristata
• Fish production
• Economic benefit