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The chestnut moray, or panamic green moray (Gymnothorax castaneus) is a common and widespread species of moray eel (family Muraenidae) native to in the subtropical and tropical eastern Pacific waters from the gulf of California to Ecuador and archipelagos including the Cocos Islands and the Galapagos. A robust fish, it grows to about 1.5 meters (4.5 feet) long. Gymnothorax castaneus inhabits holes and crevices in rocky reef environments up to 35 meters (100 feet) deep, though the very dark colored juveniles sometimes live in mangrove swamps. The chestnut moray is identifiable by its green brown color and white flecking on the dark dorsal fin (Discover Life 2015). An aggressive carnivore, the chestnut moray feeds in the open at night on small fish and mobile invertebrates such as crustaceans, octopus and squid. Like most morays, during the day it usually stays with its body concealed in a shelter, often protruding its head from the hole (McCosker and Béarez 2010).
Moray eels have been documented as a primary “nuclear fish” species, i.e. disruptive feeders that scatter remains or flush out food sources, and in so doing attract opportunistic heterospecifics. In the Sea of Cortez, Strand (1988) observed that chestnut morays, no matter what their activity, are consistently trailed by multiple opportunistic followers of several species, for periods of time considerably longer than trailing fish followed any other “nuclear fish.” These feeding associations sometimes involve fish with diets overlapping that of G. castaneus, causing occasional aggression between moray and followers (Strand 1988).