Abstract
Hatchery-reared Japanese flounder Paralichthys olivaceus usually exhibit body color anomalies (hypermelanosis) on the blind side, which enable released fish to be distinguished from wild fish. Through our 54 fish market surveys carried out for 4 markets in Fukushima Prefecture, such body color anomalies were also found in wild fish with the frequency of 1.2%, i.e. 130 individuals of the total 10970 fish. Twenty-nine wild individuals had evident color anomalies and were recognized as the released fish at the markets. The color anomaly patterns of the wild fish were different from the released fish and were classified into five types. Dorsal ray counts, which largely differed between the wild and released fish in this area, were useful to confirm the discrimination between the wild and released fish.
