Creature Feature: Halfmoon

halfmoonHalfmoon are primarily a Southern California fish, although they have been found as far north as the Klamath River in northern California. They are particularly common around the Channel Islands and Santa Catalina Island over shallow rocky areas and near kelp beds. Halfmoon have been observed as deep as 130 ft., but are most commonly caught in waters from 8 to 65 ft. deep.

Distinguishing Characteristics

  • Dark blue above, shading to blue-gray on the sides, becoming white below
  • Body is oval shaped (from side view)
  • Head is blunt and rounded
  • Small mouth
  • Tail is half-moon shaped
  • No spines on the gill cover (helps to distinguish it from rockfish)
  • Soft rays of the dorsal fin are nearly hidden by a thick sheath of scales

Life History & Other Notes
Halfmoon feed on a variety of plant and animal matter including algae, small invertebrates, and sponges. In the turbulent areas off rocky coasts they may be seen chasing and catching bits of surging seaweed.

Spawning takes place during the summer months. The eggs and young are free-floating, with the young generally found some distance from shore. Only adults are commonly found close to shore. Halfmoon reach maturity at about 7½ inches in length.

Halfmoon are easy to catch throughout the year. They are scrappy fighters, and good eating. Anglers fishing from rocky shores have good success for this species using mussels and shrimp; they are also caught on moss bait. Anglers fishing away from shore are most successful using fresh cut bait such as anchovy, sardine, or squid.

Halfmoon Quick Facts:

Scientific Name: Medialuna californiensis

Other Common Names: Catalina blue perch, blue bass

Range & Habitat: Klamath River south, but mostly in Southern California over shallow rocky areas and kelp beds

Length: To 19 in. and ~5 lb.

Diet & Suggested Bait: Feeds on algae, small invertebrates, and sponges. Try mussels, shrimp, anchovy, sardine, squid, or moss for bait.

Excerpt from the California Finfish and Shellfish Identification Book.

Single copies of the book are available to California residents free of charge by emailing a request to