Effect of varying species ratios of silver carp (hypophathalmicthys molitrix) and mrigal (cirrhinus mrigala) at constant density on pond fisheries in composite fish culture

摘要

Composite culture of Indian major carps and Chinese carps result in high yield as they better consume the existing natural food resources due to differences in their feeding behavior. Silver carp is a filter feeder, feeding on phytoplankton dominantly while the Mrigal carp is a bottom feeder, living on debris that settle to the bottom. During this project two ponds were stocked with different ratios of Indian Major Carps viz; Labeo rohita , Cirrhinus mrigala , Catla catla , and Chinese Carps viz; Hypophathalmicthys molitrix and Ctenopharyngodon idella . NH_4-NO₃ and SSP (0.01gm N/cm) were used as inorganic while poultry manure (0.1% N) was used as organic source of fertilizer. Various fish growth parameters such as body weight, total length, fork length of fish and the yield were taken into consideration to assess the effect of varying species ratios. Pond stocked with lower ratio of Labeo rohita produced higher production of Hypophathalmicthys molitrix . The pond where Hypophathalmicthys molitrix were greater in number, the production of Cirrhinus mrigala was lower. This indicates that there might have been competition for food resources and so a lower stocking ratio of Hypophathalmicthys molitrix is more favorable. Most of the ecological parameters such as temperature, light penetration, dissolved oxygen, pH, alkalinity, carbonates, bicarbonates, chlorides, and total hardness and calcium showed significant seasonal differences.