Faculty of Agriculture, Kinki University, Nara 631-8505, Japan
The original population of the Ikehara Reservoir consisted of a subspecies of the largemouth bass, Micropterus salmoides salmoides. In 1988, another subspecies, M. s. floridanus, originating from Florida was transplanted there. In 1996/97 a genetic study was made on the population in regard to their mitochondrial (mt) DNA with the result that M. s. floridanus was detected from 56.8% of fish. We re-examined the population in 2003 and found that fish having the mtDNA originating from M. s. floridanus accounted for a significantly higher percentage than before (86.7%). Moreover, fish having the mtDNA originating from M. s. floridanus were found from other lakes and ponds in the Kinki District.