Halfmoon

Medialuna californiensis

Halfmoon

Medialuna californiensis

Other Common Names
Catalina Perch, Catalina Blue Perch

Connected Coasts

Other Common Names

Catalina Perch, Catalina Blue Perch

At the Aquarium

Connected Coasts

Appearance

Halfmoon are blue to dark gray on their backs which fade into the silver of their belly area. Some are grayish blue all over. They have a large blackish blotch above their gills. Halfmoon also have faint slanted stripes on their sides.

Halfmoon can grow up to 48 cm.

Habitat

Rocky areas and kelp beds at depths up to 40 m.

Diet

Seaweed and small invertebrates.

Life History

Fertilized eggs and hatched larvae float in the water column and drift with ocean currents. They then enter a juvenile stage where they join small schools in near-shore areas and around floating masses of kelp. Halfmoon continue their juvenile development in these habitats. They reach maturity when they grow to about 19 cm.

Halfmoon typically live from 1 to 8 years.

IUCN Status

Least Concern

Ecosystem & Cultural Importance

Halfmoon support kelp forest ecosystems. Since they eat kelp they help control kelp growth. They are also prey to a variety of predators including sea lions, seals, larger fish, several species of marine birds, and occasionally bald eagles.

Halfmoon can be an important part of recreational fishing, depending on the year.

Only found in the Eastern Pacific from Canada to the Gulf of California.

Even though halfmoon can be found as north as Vancouver Island, Canada, this species is rare in areas north of Point Conception, California.

Halfmoon and blacksmith fish are often confused for one another since they are very similar in color. Blacksmiths are much smaller than halfmoon, only growing as long as about 30 cm.

The common name of these fish comes from the shallow curved shape of their caudal fin that looks similar to a crescent or half moon.

Citations & Other Resources

Ken Chan, Long Beach Aquarium of the Pacific (1067894299), CC BY-SA 2.0
Allen, G., R. Robertson, and B. Lea. 2010. Medialuna californiensis. The IUCN Red List of Threatened Species 2010.
CA Marine Species Portal. (n.d.). . https://marinespecies.wildlife.ca.gov/halfmoon/false/.
California Sea Grant (n.d.). Halfmoon/Blue Perch https://caseagrant.ucsd.edu/seafood-profiles/halfmoonblue-perch.
Kells, V. A. 2016. A field guide to coastal fishes. From Alaska to California. Johns Hopkins University Press, Baltimore.
Snyderman, M. 1998. California marine life: a guide to common marine species. Roberts Rinehart Publishers in cooperation with Monterey Bay Aquarium, Niwot, Colo.
Stevens, E.G., W. Watson and H.G. Moser. 1989. Development and Distribution of Larvae and Pelagic Juveniles of Three Kyphosid Fishes (Girella nigricans, Medialuna californiensis, and Hermosilla azurea) off California and Baja California. Fishery Bulletin, US. 87: 745-768.

Halfmoon

Halfmoon

Other Common Names

At the Aquarium

Appearance

Habitat

Diet

Life History

IUCN Status

Ecosystem & Cultural Importance

Citations & Other Resources

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