Effect of Water Level Disturbance on Shallow Eutrophic Ponds as the Conservation Method of Aquatic Environments.

— Low Density Management for Invasive Crayfish Procambarus clarkii and Ripple Effects —

Abstract

There are many cases where eutrophication has become a common in irrigation pond, remarkable in ponds because the use of agricultural land irrigation has been abolished and it is operated as a park pond. Regular water drying is no longer carried out in these park ponds. Ecological disturbances such as water level fluctuation has disappeared in these ponds, and overgrowth of certain alien species is observed. Artificial water level disturbances were revived in these ponds, increasing predation pressure by birds on invasive crayfish Procambarus clarkii and bullfrog Rana catesbeiana. As a result, low density management of invasive crayfish and bullfrog was successful. The overgrown area of aquatic plants has expanded, and the population density of zooplankton such as Cladocera has increased. The effect spread widely to the biota through the food web, and the effect on water environment conservation was confirmed.