The reproductive ecology of an endangered cryprinid, Pseudorasbora pumila subsp. sensu Nakamura (1969), was elucidated by examination of the spawning substrate. A field experiment indicated that oviposition in P. pumila subsp. was restricted to relatively large (>91 cm3) stones in shallower depths (< 37 cm). Another “choice” experiment showed that P. pumila subsp. oviposited almost always on the bricks, whereas a related species Pseudorasbora parva preferred the sticks. The bricks were sometimes occupied by Procambarus clarkia, and the oviposition of P. pumila subsp. was negatively correlated with the presence of P. clarkia. The reproductive behavior of P. pumila subsp. was recorded using a waterproof video camera, characteristic behavior including bottom digging, egg/substrate cleaning, ovipositing and egg eating being observed. Because the size and depth of stones play a vital role in reproduction of P. pumila subsp, conservation effort for this subspecies should include the shallow placement of large stones in suitable habitat.
