Abstract
In 18 marine fish species from the eastern Mediterranean, vertical mouth opening increased linearly with total length ( L T ) for 10 species and log‐linearly for eight species. Horizontal mouth opening was linearly related to L T for 12 species and log‐linearly for six species, whereas mouth area was a log‐linear function of L T for all fish species examined. Mouth shape varied greatly covering the whole spectrum from a full circle to an extended oval. In addition, the trophic level of the 18 species could be expressed as an asymptotic function of mouth area. The results are discussed within the context of the trophic ecology of the species examined in the study area.