The present study investigated the spawning behaviour of the spiny eel, Macrognathus pancalus, and its relationship with the environment (photoperiod and temperature). The results show that M. pancalus breeds during February to September with peak spawning during February/March and July/August, indicating two main breeding periods. Initiation of breeding occurs during increasing day lengths in early spring (February/March), and regression during decreasing day lengths in autumn (September/October). The breeding status confirmed by gonadosomatic index (GSI) and ovarian histology showed six stages of ovarian maturation (viz. stage I: chromatin nucleaolar; II: perinucleolar; III: cortical alveolar; IV: vitellogenesis; V: ripe; and VI: partially spent), with predominance of one or more stages at a particular time of the year. Males also followed a similar seasonal pattern in gonadal maturation as reflected by their GSI. Results show that M. pancalus is a seasonal breeder with bimodal spawning activity. The breeding pattern suggests an influence of prevailing day length conditions at this latitude.