Examination of sites and timing for temporary relocation of lotic unionid mussels toward land readjustment.

Abstract

To determine the suitable sites and timing for temporary relocation toward land readjustment, the growth, survival, and disappearance of three species of lotic freshwater unionid mussels were investigated for two years after pilot relocation. Higher growth and survival and lower disappearance of the relocated mussels were observed in the irrigation pond, indicating that this is the most suitable site for relocation. Higher growth, survival, and disappearance were observed in the branch canal, indicating that the branch canal can be used as a relocation site if prevention measures are taken against hydraulic displacement of mussels. In the main canal, mussel growth was limited and showed lower disappearance but lower survival, indicating that the main canal is the least suitable relocation site. However, appropriate flow management can facilitate mussel relocation to the maincanal. Higher growth and mortality were observed in the warm season （May-October） and higher displacement in the typhoon season （August-October）, suggesting that mussel relocation should be implemented in winter. General recommendations for temporary relocation of lotic mussels are also suggested based on our results.