Two-dimensional otolith size trends in myctophid fishes.

Lanternfishes are a key food source for marine and terrestrial predators, and play an important role in energy transfer between surface waters and deeper layers. This study investigates otolith size variation in 105 myctophid species included in the AFORO database. The study covers the five Myctophidae subfamilies: Diaphinae, Gymnoscopelinae, Lampanyctinae, Myctophinae and Notolychninae. Several measurements were taken from the otoliths, and relative shape and sizes indices were calculated for the different fishes. Morphometric analyses revealed that Diaphinae and Gymnoscopelinae possess the largest otoliths in terms of length and width, whereas Notolychninae exhibited the smallest. Gymnoscopelinae were further characterized by more elliptic otolith shapes, while Diaphinae displayed proportionally larger otoliths relative to fish size. Non-linear regression between otolith length and fish length was performed for 59 species, providing complementary data for understanding prey-predator relationships. Also, loess regression between the otolith relative size and fish size showed different growth patterns among species, which could suggest dissimilar metabolic activity. Our study provides a tool that will improve future food webs and ecological studies on otolith size in other fish taxa.