Catadromy describes an array of migration behaviours which are expected to generate different patterns of genetic structure; from total panmixia (genetic homogenisation) to moderate structure with isolation by distance. In this study, the genetic structure of the circumtropical sea mullet (Mugil cephalus) along approximately 550km of the Queensland coastline was investigated. Using six highly variable microsatellite loci, no signifi cant genetic structure was detected (FST < zero), despite high genetic diversity providing suffi cient power to detect structure. These patterns of genetic structure were concordant with other studies of M. cephalus at similar scales in other parts of the world. Overall, genetic structure for M. cephalus is similar to that of many marine species, which also show panmixia along this section of the Queensland coast. Conservation of this species should focus on ensuring freshwater-marine migration is not diminished.