←Species
Kyphosidae
Halfmoon
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Field guide · §4.26

Halfmoon

◐
Medialuna californiensis
Kyphosidae (sea chubs — same family as opaleye)
Water
60-68°F
Best time
Diurnal
Tide
Incoming
Robert's pick

How to catch a halfmoon

Bait
Mussel meat, fava bean, peeled shrimp, frozen pea
Rig
Float rig with small #6 baitholder hook, 10 lb mono, 15" leader
Technique
Chum lightly with crushed mussel near kelp paddies, let halfmoon school come up. Free-line a small bait. They'll spit unfamiliar baits — natural offerings work best.
When to target

Seasonality

Year-round at kelp; best summer (May–September) when water warms past 62°F.

When they bite
Tide preference
Incoming through high — grazes the kelp on rising water
Time of day
Diurnal — midday peak
Pressure
Any
Sources
  • · CDFW Halfmoon species page
  • · Allen et al. (2006)
Full citations in SPECIES-EVIDENCE.md §4.26.
← All species·§4.26 in SPECIES-EVIDENCE.md

Halfmoon

◐
Medialuna californiensis
Kyphosidae (sea chubs — same family as opaleye)Prefers 60–68°F
Habitat & range

Where they live

CA range
Gulf of California → Vancouver Island
Habitat types
Rocky reef + kelpJetty into sandOpen coast kelp
Water temp
60–68°F preferred
Life history

Biology

Lifespan~10 years
Size at maturity~10" / ~3 years
SpawningJuly–September, pelagic eggs
SchoolingSchools of 10–50 fish along kelp edges
DietAlgae, kelp, small crustaceans, polychaete worms
Behavior

When they bite

Tide preferenceIncoming through high — grazes the kelp on rising water
Time of dayDiurnal — midday peak
Pressure biasAny
Field ID

How to identify

Blue-gray oval body (the "half-moon" curve), small mouth, slightly forked tail, dark dorsal fin with white edge in some specimens

Look-alikes

Opaleye (browner-olive, distinctive blue eye); pile perch (deeper body, different fins)

Robert's pick

How to catch

Best baitMussel meat, fava bean, peeled shrimp, frozen pea
Best rigFloat rig with small #6 baitholder hook, 10 lb mono, 15" leader
TechniqueChum lightly with crushed mussel near kelp paddies, let halfmoon school come up. Free-line a small bait. They'll spit unfamiliar baits — natural offerings work best.
California regulations
No specific size limit, general regulations apply. License required ages 16+.

Always verify current regulations on the CDFW site.

Where to fish for Halfmoon

SoCal hotspots

Top spots from the doc: Catalina kelp · PV coves · La Jolla kelp · PB jetty (rocky end) · Sunset Cliffs
All spots in the TideRead catalog that target Halfmoon (0):
No catalog spots currently list this species — audit pending.
Seasonality

When to target

Year-round at kelp; best summer (May–September) when water warms past 62°F.

Table fare

If you keep it

Decent — mild but slightly soft. Best fried or in fish tacos. Bleed at the gills.

⚠ Safety & handling

Before you grab it

No real hazards. Easy handling species.

Common mistakes

What anglers get wrong

Often called "blue perch" — they're NOT a perch (Embiotocidae). They're sea chubs (Kyphosidae), close cousins to opaleye.

Did you know

Halfmoon are largely herbivorous — like opaleye, they graze algae and kelp. Anglers consistently underestimate their fight; pound-for-pound they pull hard for a 'pretty fish.'

Sources
  • · CDFW Halfmoon species page
  • · Allen et al. (2006)
Full citations + cross-references in SPECIES-EVIDENCE.md §4.26.