Breeding season, spawning time, and description of spawning behaviour in the Japanese ornate dragonet, Callionymus ornatipinnis: a preliminary field study at the northern limit of its range.

Abstract  The reproductive behaviour of the Japanese ornate dragonet (Callionymus ornatipinnis) was studied at the northernmost limit of its distribution at Usujiri in southern Hokkaido, Japan. Field observations confirmed that C. ornatipinnis reproduced at Usujiri, and this is the first detailed description of the reproductive behaviour of C. ornatipinnis. Males were observed to swim continuously in a sandy area where females were abundant, persistently approaching females and performing courtship displays. Courtship behaviour consisted of males spreading their fins in front of females. If a female accepted a male for spawning, the pair would then ascend upward 0.7–1.2 m from the sandy bottom and release their pelagic eggs. Spawning, which occurred daily at dusk for approximately 1 h and ceased when it became dark, was related to water temperature and was only observed when water temperature exceeded 19°C. The breeding season of this species at Usujiri spanned only the month of September, which is considerably shorter than that of other dragonet species inhabiting temperate waters. The short breeding season was probably attributed to the fact that the water temperature at Usujiri only exceeds 19°C in the month of September. [ABSTRACT FROM AUTHOR]