Medialuna ancietae is a species of sea chub native to the Pacific coast of South America where it inhabits the giant kelp forests.

[2] Sea chubs are medium-sized fish with small heads, blunt snouts and laterally compressed bodies.

[4] M. ancietae is native to the subtropical southeastern Pacific Ocean where it is found on the coasts of Peru and Chile.

[6] Medialuna ancietae is esteemed as a sport fish and is the subject of both recreational and artisanal spear-fishing.

Historically, along with Graus nigra and the Chilean sheepshead (Semicossyphus darwini), M. ancietae constituted more than 98% of the fish caught by spear-fishing.