Panamic Green Moray, Gymnothorax castaneus
The Panamic Green Moray, Gymnothorax castaneus, whose common Spanish name is morena verde panámica, is a member of the Muraenidae or Moray and Snake Moray Eels Family, known collectively as morenas in Mexico. The fish is also known as the Chestnut Moray. Globally, there are 116 members in the genus Gymnothorax, of which 18 are found in Mexican waters, nine in the Atlantic and nine in the Pacific.
The Panamic Green Morays have stout elongated compressed bodies that taper gradually to a rounded tail. They have various shades of green, greenish-brown, and brown; some fish have small white spots. They quickly fade to a uniform dark brown upon death. They have a large black spot covering their gill openings. Their head is large with a pointed snout and small eyes. Their front nostrils have tubes and their rear nostrils do not. Their large mouth is equipped with visible canines and smaller conical unserrated teeth with one row on the side of the top jaw and three longitudinal rows at the front. Their well-developed anal and dorsal fins are covered with skin and continuous with the caudal fin. Their dorsal fin originates in front of the gill openings. Their tail is approximately half or slightly greater than half the body length. They have no pectoral fins or scales. They are covered with thick yellow mucus, which provides them with protection from abrasion.
The Panamic Green Morays are found in shallow reef areas within cracks and crevices from the intertidal zone to depths of 330 feet. They reach a maximum length of 1.5 meters (5 feet 11 inches). Only their head protrudes during the day. Their body shape and lack of fins, scales, or gill covers allow them to move quickly in and out of rocky crevices. They are voracious nocturnal ambush predators with poor eyesight that utilize their keen sense of smell to seek out prey, consuming small fish and invertebrates including crab, octopus, and shrimp. They open and close their mouth frequently, an action required for respiration. Reproduction is viviparous with eggs and sperm broadcast into the water generating pelagic eggs and larvae that can drift in oceanic currents for up to a year before settling out on the bottom. They are found in all Mexican waters of the Pacific with the exception of the extreme northern portion of the Sea of Cortez and north of Guerrero Negro along the northwest coast of Baja. They are a poorly studied and poorly documented species and very little is known about their behavior patterns.
The Panamic Green Moray can be confused with the Finespotted Moray, Gymnothorax dovii (omnipresent small white spots covering all parts of body behind head) and the Slenderjaw Moray, Enchelycore octaviana (beak-like head profile; uniformly-colored body; no distinguishing marks).
The Panamic Green Morays are of limited interest to most and normally a “catch and release”. Visually they are most intimidating but are very timid and not harmful. They seldom bite humans.