Freshwater mussel (family Unionidae) utilization for oviposition by Sarcocheilichthys variegatus variegatus was investigated in a drainage ditch and the Harai River. Twenty five freshwater mussels in Pronodularia japanensis (4% of 616 individuals examined) in a drainage ditch connected to the Kushida River hosted S. v. variegatus eggs, compared with none of two other freshwater mussel species, Inversidens brandti and Unio douglasiae douglasiae. In the Harai River, eight freshwater mussels (3 I. brandti, 2 Obovalis omiensis, 1 Lanceolaria grayana and 1 Anodonta spp.) (2.7% of 290 individuals examined) hosted S. v. variegatus eggs, compared with none of P. japanensis and U. d. douglasiae. Among the available freshwater mussel species, U. d. douglasiae may be only one selected against for oviposition by S. v. variegates.
