Wakahata Marsh Iron Fish Habitat

Tetsugyo are crucian-carp-like fish with elongated fins and variable colors, including iron-gray, red and white. Although several origins were proposed, a 2015 study found genetic evidence of hybridization between goldfish and Japanese crucian carp in fish from Yutori-numa Pond. That habitat in Kami, Miyagi, is a national Natural Monument; the Wakahata Pond habitat in Yamagata and the tetsugyo at Hōnenji Temple in Mie have prefectural designations.