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Species: Medialuna californiensis, California halfmoon

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above operculum - dark blotch
D IX-XI, 22-27, spiny part much lower

Medialuna californiensis (Steindachner, 1876)

California halfmoon

Body an elongate oval, compressed;  small pointed head; mouth is small, horizontal and opens at the front; the top jawbone slips partially under the under-eye bone when the mouth is closed; teeth pointed, 1 row on each jaw; dorsal fin continuous, IX-XIspines that fold down into a scaly groove, 22-27 rays, spiny part much lower than soft part; anal III, 17-21; tail fin slightly concave; paired fins are relatively short; origin of the pelvics behind the base of the pectoral fin; scales small, thick and rough, covering the body, head (except forward of eyes) and soft portions of the median fins.
Dark bluish grey to grey above, paler below; sometimes indistinct narrow short bars along flank; a dark blotch above upper corner of operculum; dorsal, tail and anal grey, dark outer margins; upper and lower edges of tail fin narrowly white; juveniles blue above, silvery below.
Size: 48.3 cm.
Habitat: rocky bottoms and algal beds.
Depth: 0-44 m.
Canada to the SW Gulf of California.

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  • Marine Only
  • Marine
  • Inshore Only
  • Inshore
Water Column Position
  • Bottom
  • Near Bottom
  • Bottom + water column
  • Water column
  • Submerged vegetation
  • Rocks
  • Reef only
  • Reef (rock/coral/oyster)
  • Reef associated (reef + edges-water column & soft bottom)
FishBase Habitat
  • Demersal
Feeding Group
  • Ectoparasite cleaner
  • Data
  • Omnivore
  • Data
  • Sessile worms
  • Benthic macroalgae/seagrasses
  • Ectoparasites
  • Sessile molluscs
  • Benthic microalgae
  • Sessile crustacea
Egg Type
  • Pelagic
  • Pelagic larva
  • No data
Global Endemism
  • TEP non-endemic
  • East Pacific endemic
  • All species
Regional Endemism
  • Continent only
  • All species
  • Temperate Eastern Pacific, primarily
  • California province, primarily
  • Continent
  • Tropical Eastern Pacific (TEP) non-endemic
  • Vagrant
Climate Zone
  • Northern Subtropical (Cortez Province + Sinaloan Gap)
  • North Temperate (Californian Province &/or Northern Gulf of California)
IUCN Red List
  • Least concern
  • Listed
  • Not listed
Length Max
  • 48.3
Depth Range Min
  • 0
Depth Range Max
  • 44