Pond management strategies for small-scale aquaculture in northern Vietnam: fish production and economic performance

The traditional pond aquaculture in northern Vietnam is a plant-based integrated aquaculture system using poor-quality pond inputs (macrophytes, farm by-products, manures). Most applied feeds are palatable solely to the grass carp (Ctenopharyngodon idella), which is the main species in traditional fish polyculture. Secondary species are malnourished as the natural food productivity is diminished by uncontrolled water flow through and high turbidity. Mass mortalities of grass carp lead to high financial losses for the farmers. To improve the fish production, researchers developed a semi-intensive pond management in stagnant water in which common carp was cultured as the main species with supplemental fertilization and pelleted feeds based mainly on locally available resources. In this study, the traditional and semi-intensive pond management was compared in six ponds for fish production, nutrient efficiencies and economic net benefit. The use of higher-quality feed and fertilizer inputs under semi-intensive pond management resulted in higher fish yields of 228 +/- A 42 kg x 1,000 m(-2) compared to 88 +/- A 44 kg x 1,000 m(-2) under traditional management and higher net economic benefit of 3,848,000 +/- A 1,469,000 VND x 1,000 m(-2) under semi-intensive compared to 846,000 +/- A 3,753,000 VND x 1,000 m(-2) under traditional management. Under semi-intensive management, 11.5 % of applied total nitrogen was transferred into fish biomass while under traditional management, 4.4 % of applied total nitrogen converted into fish biomass.