Beneficial effects of fish stocking on performance and pest control in the lotus field system

Abstract

The present study was conducted to evaluate the economic effects of fish stocking on plant and fish performance in lotus fields, as well as to determine its influence on controlling common pest species associated with lotus fields. Lotus yield, fish growth performance, economic returns and pest abundance at 5 fish stocking density treatments (0, 1500, 3000, 4500 and 6000 ind. ha-1) were determined in 15 separate lotus fields at a lotus farming facility in Wugang City, Hunan Province, China. The results showed a tendency for the lotus yield to increase with fish stocking density, but significant differences were not found among the treatments. Survival rates were not significantly different among the fish stocking treatments for the 3 species of carp tested. Absolute growth rate and specific growth rate showed similar trends, with their values significantly decreasing as stocking density increased for each carp species. The total yield for the 3 fish species did show significant differences, with the highest yield in the 6000 treatment and the lowest in the 1500 treatment. Total net income was highest in the 4500 treatment and lowest in the control (0) treatment. No significant differences were observed between the 4500 and 3000 treatments. The abundance levels of 3 types of pests were lower in the fish stocking treatments than in the control treatment, and were shown to decrease with increasing stocking density. Based on these observations, stocking densities of 3000 to 4200 total ind. ha-1 were considered optimal levels in lotus-fish culture systems.