Day and night mesopelagic fish assemblages off the Kerguelen Islands (Southern Ocean)

Mesopelagic fish assemblages were investigated in the Polar Frontal Zone of f the Kerguelen Islands during summer 1995, in parallel with a king penguin tracking study. During the day, the upper offshore water layers (0-200 m) have low potential prey diversity and abundance with only three fish specie s: a lanternfish, Krefftichthys anderssoni, a member of the Muraenolepidida e, Muraenolepis marmoratus, and the early stages of the nototheniid, Lepido notothen squamifrons. The mesopelagic fish community, including the typical myctophids, first appears in the deeper layer (300 m). At night, the surfa ce layer (50 m) is invaded by the mesopelagic Myctophidae Electrona antarct ica, Gymnoscopelus braueri, G. piabilis, G. fraseri, G. nicholsi, Protomyct ophum bolini and P. tenisoni. Deeper ( > 100 m), a dine of species assembla ges from the coast to offshore is observed.