[2] Mullets are distinguished by the presence of two separate dorsal fins, small triangular mouths, and the absence of a lateral line organ.

[7] Fish with common names including the word "mullet" may be a member of one family or the other, or even unrelated such as the freshwater Catostomus commersonii.

[8] However, recent taxonomic work has reorganised the family and the following genera make up the Mugilidae:[9][2] A common noticeable behaviour in mullet is the tendency to leap out of the water.

The reasons for this lower jump are disputed, but have been hypothesised to be in order to gain oxygen rich air for gas exchange in a small organ above the pharynx.

[11] The previously understudied osteological development of Mugil cephalus was investigated in a 2021 study, with four embryonic and six larval developmental steps being described in aquaculture-reared and wild-caught specimens.