Fatty Acid Spectra in Mesopelagic Fishes of the Myctophidae and Stomiidae Families Collected in the North East Atlantic

New data on the fatty acid compositions of muscle tissues two most widespread families mesopelagic zone—the Myctophidae (Notoscopelus kroyeri and Symbolophorus veranyi) Stomiidae (Chauliodus sloani, Stomias boa, Borostomias antarcticus, Malacosteus niger) families—were obtained from Irminger Sea (North East Atlantic). The acids (FAs) in total lipids (TLs), phospholipids (PLs), triacylglycerols (TAGs), cholesterol esters waxes were analyzed using gas–liquid chromatography with a mass-selective detector flame-ionized (GC-MS GC-FID, respectively). Species-specific differences FA/alcohol profiles studied fishes revealed. A directed deep-vise trend changes content performance certain FAs for species was found. Along this, general character dominance monounsaturated (MUFAs), which discussed as food tracers, MUFAs included dietary markers zooplankton (copepods)—20:1(n-9) 22:1(n-11), varied association species—such that biomarker Calanus glacialis predominated muscles B. antarcticus C. hyperboreus prevailed other species. Different strategies compensatory adaptation to depth gradient lipid metabolism among discussed.