Gymnothorax castaneus reaches 150 cm. Large Eastern Pacific moray with uniform chestnut-brown body (hence castaneus) to dark olive-brown, without contrasting patterns. Lives from 3 to 40 m in crevices, caves and fissures of rocky reefs from Gulf of California to Peru, Galapagos. Nocturnal predator of fish and cephalopods. One of the largest Eastern Pacific morays. Iconic photo subject of Sea of Cortez dives, often visible head out of hole. Eastern Pacific cousin of Indo-Pacific Gymnothorax like G. javanicus (batch 5) and Atlantic.

