Otolith morphology of mesopelagic fishes collected from the Irminger Sea, North Atlantic Ocean

A large series of otoliths of 16 mesopelagic teleost fish species from the Irminger Sea, North Atlantic Ocean, are described morphologically to investigate the ontogenetic and intraspecific variation. The results show that the surface morphology of the otoliths between young and adult specimens is variable, especially in the alepocephaliform (Normichthys operosus, Sagamichthys schnakenbecki, Xenodermichthys copei) and astronesthine (Borostomias antarcticus) species. The diagnostic features of the otoliths can be used to confirm the identity of the species, especially in myctophids, where confusion between Benthosema glaciale and Myctophum punctatum may be possible. A SEM-based iconography of the otoliths of all studied species is presented.