A total of 276 specimens of Hygophum hygomii were collected stranded along the Sicilian shoreline of the Strait of Messina between 2010 and 2018 (winter and spring). Their stomach contents were examined to study their diet.

The in-depth analysis, at family, genus, and species levels, of the prey ingested by H. hygomii enabled us to investigate the trophic ecology of this mesopelagic fish, which has to date been little studied in the Mediterranean Sea. By cross-referencing available data on prey ecology, it was possible to understand the feeding strategy of H. hygomii, including its vertical migrations. Within the broad size range of the specimens we examined (14.5–41.1 mm SL), some dietary differences appeared to be linked to predator size, particularly above 25 mm SL.

Finally, a comparison was made between H. hygomii and other Myctophids in the same study area, highlighting differences and similarities in their feeding strategies.

The study of mesopelagic fishes is essential for a better understanding of pelagic food webs. Indeed, due to their large biomass and gregarious behavior, together with the well-known daily vertical migrations, these fish play a crucial role in energy transfer along the water column and across trophic levels. Their diet, based primarily on herbivorous zooplankton, and their role as prey for larger organisms (e.g., tuna, cephalopods, dolphins) are important in this regard.

Therefore, deepening our knowledge about mesopelagic fish allows us to gain insights into marine ecosystems and their health, including by studying the presence of contaminants (e.g., microplastics, heavy metals) and their passage through the food web, from plankton to large predators.