The European eel , Anguilla anguilla ( L . ) , ifl Japanese waters

To gain information about the relative proportion of introduced anguillid eel species inhabiting Japa nese natural waters, 98 eels were collected and genetically identified — 46 from the Uono River, Niigata, Japan, during their downstream spawning migration, and 52 silver eels from the East China Sea. Species identification using RFLP analysis of the mitochondrial 16SrRNA domain suggested that the European eel, Anguilla anguilla, was more abundant (93.5%) than the Japanese eel, A. japonica, (4.3%) in the Uono River. One specimen was identified as American eel, A. rostrata, which is the first record of gen etic identification of this species in Japanese waters. In addition, a migrating European silver eel was identified among the sample of silver eels in the East China Sea. The genetic species identification of these specimens was in agreement with the morphological data. The present study suggests that import ed Atlantic cds develop normally to metamorphosis into the silver phase and then begin the oceanic spawning migration.