Shorefishes of the Greater Caribbean online information system

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Species: Nomeus gronovii, Man-of-war Fish

All Families:   All Genera:   All Species:

elongate, firm
eye with fatty ring
D origin behind pectoral base
adult brown, juvenile blue + black spots
tongue: no teeth
pelvic: origin before/under pectoral base, of juvenile - very large
A II, 24-29

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: 0-1000 m.

Worldwide in warm temperate and tropical seas. North Carolina to the S Caribbean.

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  • Marine
  • Marine Only
  • Offshore
  • Offshore Only
Water Column Position
  • Mid Water
  • Near Surface
  • Surface
  • Water column only
  • Water column
  • Jellyfish
FishBase Habitat
  • Pelagic
Feeding Group
  • Carnivore
  • Data
  • Planktivore
  • Data
  • Zooplankton
  • Pelagic jellyfish/ctenophores
Egg Type
  • Data
  • Pelagic
  • Pelagic larva
Global Endemism
  • All species
  • Circumtropical ( Indian + Pacific + Atlantic Oceans)
  • Greater Caribbean non-endemic
Regional Endemism
  • Also in Brazil
  • Continent
  • Continent + Island (s)
  • Extends N + S of GC
  • Extends North of GC
  • Extends South of GC
  • GC non-endemic
  • Island (s)
  • All species
  • Resident
Climate Zone
  • Equatorial (0-10N, Costa Rica / Venezuela)
  • Subtropical (23-35N, Florida / Carolinas / Bermuda)
  • Temperate (>35N)
  • Tropical (10-23N, Nicaragua / Cuba)
IUCN Red List
  • Least concern
  • Listed
  • Not listed
Length Max
  • 40
Depth Range Min
  • 0
Depth Range Max
  • 1000