Last modified: May 6, 2019

Fish Sea Chubs and Damselfish


Sea Chubs: Family Kyphosidae

Species: Medialuna californiensis (Steindachner, 1876); from the Spanish word medialuna (halfmoon, referring to the shape of the tail) and californiensis (California, where first found).

Alternate Names: Catalina blue perch, island mackerel, blooper, blue wizard, blue perch or blue bass. In early days sometimes called medialuna. In Mexico called chopa medialuna.

Identification: Halfmoon are perch-shaped but heavier bodied; they’re similar in many ways to opaleye. Their coloring is normally bluish-black above, bluish-gray on sides, and light blue below. Their tail is shaped like a half-moon.

Size: Although a record-size fish measured 19-inches and weighed 4 pounds 12.5 ounces, the vast majority that are caught are less then one foot in length. Smaller fish are sometimes found in large schools while the larger fish seem more solitary.

KJ and a halfmoon from the Cabrillo Mole 

Range: Gulf of California to Vancouver Island, British Columbia.

Habitat: Halfmoon are found in shallow-water, rocky areas and kelp beds. They’re often in small loose schools in the mid-water area and, at times, mixed in with schools of pileperch.

Piers: Common at southern and central California piers that are located near rocks, reefs or kelp. They’re common as far north as Cayucos but occasionally taken as far north as Santa Cruz. Best bets: Ocean Beach Pier, the Green Pleasure Pier (Avalon), Cabrillo Mole (Avalon), Hermosa Beach Pier, Redondo Harbor Sportfishing Pier, Santa Monica Pier, Gaviota Pier, and the Paradise Cove Pier.

Shoreline: A common catch of rocky shore anglers in southern California.

Boats: Although mainly considered an inshore species, quite a few are landed by anglers fishing from boats, especially at Catalina.

Bait and Tackle: Halfmoon will take almost any bait but they prefer fresh mussels, shrimp, or small crabs. When schools are present, a small strip of squid will often work, and you will lose far less bait. Halfmoon caught from boats seem to be less picky and will often hit pieces of anchovy, sardine, or squid.

Boats: Although mainly considered an inshore species, quite a few are landed by anglers fishing from boats, especially at Catalina.

Jimbojack and a halfmoon from the Cabrillo Mole

Food Value: A good eating, mild-flavored fish.

Comments: Halfmoons are good fighters, very similar to opaleye and the larger perch. They will eat almost anything in their environment including red, green, and brown algae, sponges, bits of seaweed, green moss, shrimp, mussels, squid, and fish. Apparently they have a hard time deciding whether to be vegans or meat-eaters and that may explain their scrappy and perhaps irritable nature.


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