Abstract
The captured Inversiunio jokohamensis individuals and their inhabiting environment were investigated in the east side ditch (Site 1, drying up ditch) and the west side ditch (Site 2, not drying up ditch) in a valley after a period of temporary drying up to assess the influence of drying up on the Inversiunio jokohamensis individuals in Site 1 and consider ditch structure to relieve the influence on September 18 and October 24, 2010. As a result, the ratio of dead individuals and the body length distribution had a significant difference between both sites P < 0.01 ). In addition, dead individuals of all body length sizes were confirmed in Site 1. The number of individuals has decreased accompanying growing of the body length in Site 1. Methods to modify the ditch structure to relieve influence of temporary drying up are considered essential to maintain the population.
