 But the genomic analysis of one of Medaka sub-population indicates that their effective population size is around 25000-70000.Medaka has a been kept as a domesticated pet in Japan for centuries.In recent years the fish has gained further popularity, with some rarer breeds valued at over 1 million yen (approximately $10,000)—though the most common varieties (like Himedaka) can be purchased for around 50 yen per fish.