Swift swimmers. Mainly inhabit tropical and subtropical waters; however, during the feeding period adults may migrate to the subarctic reaching as far north as Greenland, Iceland and the Bering Sea (Ref. 51887). Epipelagic- and mesopelagic, from near the surface to below 1,000 m, sometimes approaching inshore waters (Ref. 6011). Bathypelagic (Ref. 58302). Mainly nocturnal. Feed on fishes, cephalopods, tunicates, and crustaceans (Ref. 6011). Preyed upon by opah, sharks, albacore, yellowfin tuna, and fur seals (Ref. 6885). For large fishes, the canibalism rate and the occurrence of large evasive prey and Sargassum seaweeds floating at the surface were greater than for small lancetfish (Ref. 75027). Often caught on tuna longlines (Ref. 58472). Cannibalism among lancetfish of the westernIndian Ocean appears to be an option for increasing adult survival during periods, or in areas of low prey abundance (Ref. 75026). May adapt its opportunistic foraging behavior, feeding on non-conspecific abundant prey such as crustaceans when available, and switching to a high level of conspecific predation in poor waters (Ref. 75026).Parasites of the species include nematode, tapeworm and a large muscular trematode (Profundiella alepisauri) (Ref. 5951).