RESUMEN
Objective To investigate the distribution and quantitative changes in each marshland of Changsha section of the Xiang River and evaluate the effectiveness of snail control in recent years.Methods A snail survey was carried out by using the systematic and environmental sampling method for 5 years.Results Twenty-four marshlands were investigated continuously from 2003 to 2007.The number of marshland with snails accounted for 77.8%,66.7%,70.8%,75.0% and 62.5% of the each investigated year,respectively.The total number of marshlands with snails were 20 that accounted for 83.3% of all marshlands investigated over the five years.The number of snails and the rate of living snails were different in each marshland,but the downward trend was significant(P