Shorefishes of the Eastern Pacific online information system

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Species: Nomeus gronovii, the Man-of-war fish

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scales extend before eyes
D: origin behind pectoral base
tongue without teeth
pelvic origin before/under pectoral base
A II, 24-29
juveniles: pelvics very large

Nomeus gronovii (Gmelin, 1789)

Man-of-war fish

Body elongate; eye large, with a fatty ring around it; mouth small, usually ends before eye; teeth small, conical, ~ 1 row on jaws; teeth on center and sides of roof of mouth, and on bases of gill arches, none on tongue; opercle thin, with 2 flat spines; gill rakers 8 + 15 -19; 2 scarcely separated dorsal fins, 1st with IX-XII spines, which fold into a groove, its origin behind (in small specimens directly over) pectoral origin, longest spine slightly longer than longest ray; anal fin I-II, 24-29; pelvic fins insert before or under pectoral base, fan shaped, attached to belly along entire length, folds into a groove; pectoral fins 19-24, long and wing-like, with oblique bases; branched mucous canal along flank; scales on head in a broad band, extending before eyes; lateral line complete, high along back. Juvenile with greatly enlarged pelvic fins and round pectoral fins, deeply forked tail fin; lateral line ends under end of dorsal fin base.

Juveniles: silvery blue with black bars and spots; pelvic fins blue-black with white blotches; adults: uniformly dark brown.

Size: reaches 40 cm.

Inhabits surface layers of the high seas; young are associated with drifting Man-of-War siphonophores (Physalia).

Depth: 0-20 m.

Worldwide in warm temperate and tropical seas. The tip of Baja California to the eastern Gulf of California to Peru and the oceanic islands.

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  • Marine
  • Marine Only
  • Offshore Only
  • Offshore
Water Column Position
  • Surface
  • Mid Water
  • Water column only
  • Near Surface
  • Water column
  • Jellyfish
FishBase Habitat
  • Demersal
Feeding Group
  • No Data
  • Carnivore
  • Planktivore
  • Pelagic jellyfish/ctenophores
  • Data
Egg Type
  • Pelagic larva
  • No data
  • Pelagic
Global Endemism
  • Transisthmian (East Pacific + Atlantic of Central America)
  • "Transpacific" (East + Central &/or West Pacific)
  • East Pacific + all Atlantic (East+West)
  • All Pacific (West + Central + East)
  • TEP non-endemic
  • Circumtropical ( Indian + Pacific + Atlantic Oceans)
  • All species
  • East Pacific + Atlantic (East +/or West)
Regional Endemism
  • All species
  • Tropical Eastern Pacific (TEP) non-endemic
  • Eastern Pacific non-endemic
  • Island (s)
  • Continent + Island (s)
  • Continent
  • Resident
Climate Zone
  • Equatorial (Costa Rica to Ecuador + Galapagos, Clipperton, Cocos, Malpelo)
  • Northern Subtropical (Cortez Province + Sinaloan Gap)
  • Northern Tropical (Mexican Province to Nicaragua + Revillagigedos)
  • South Temperate (Peruvian Province )
IUCN Red List
  • Not evaluated / Listed
  • Not listed
Length Max
  • 40
Depth Range Min
  • 0
Depth Range Max
  • 20