Panamic Green Moray, Gymnothorax castaneus

Panamic Green Moray, Gymnothorax castaneus. Fish provided by the commercial fishermen of Bahía Kino, Sonora, March 2015. Length: 71 cm (28 inches). Photograph courtesy of Maria Johnson, Prescott College Kino Bay Center, Kino Bay, Sonora.

Panamic Green Moray, Gymnothorax castaneus. Fish caught from shore off Roca de Ian, Bahia de Los Muertos, Baja California Sur, December 2021. Length: 1.06 m (3 feet 6 inches).  Mauricio Correa, Los Cabos, Baja California Sur.

Panamic Green Moray, Gymnothorax castaneus. Fish collected alive as it was walking down the beach pre-dawn at Km 21, Cabo Real, Baja California Sur, July 2008. Length: 1.10 meters (3 feet 7 inches); tail: 53%.

Panamic Green Moray Eel, Gymnothorax castaneus. Underwater photographs taken in Zihuantanejo Bay, Guerrero, March 2018 and December 2022. Photographs courtesy of Ron Woheau, Zihuantanejo.

Panamic Green Moray, Gymnothorax castaneus. Underwater photographs taken in coastal waters of the greater Los Cabos area, Baja California Sur, May 2018 and October 2019. Photographs courtesy of Bob Hillis, Ivins, Utah.

Panamic Green Moray, Gymnothorax castaneus. Underwater photograph taken in Zihuantanejo Bay, Guerrero, December 2019. Photograph courtesy of Maude Jette, Dive Zihuantanejo,  www.Divezihuantanejo.com.

Panamic Green Moray, Gymnothorax castaneus. Underwater photographs taken in coastal waters off Puerto Vallarta, Jalisco, September 2021 and July 2023. Photographs courtesy of Kevin Erwin, Seattle, Washington.

The Panamic Green Moray, Gymnothorax castaneus, is a member of the Moray and Snake Moray Eel or Muraenidae Family, that is also known as the Chestnut Moray and in Mexico as morena verde panámica. Globally, there are one hundred sixteen members in the genus Gymnothorax, of which eighteen are found in Mexican waters, nine in the Atlantic and nine in the Pacific Ocean.

The Panamic Green Moray has a stout elongated compressed body that tapers 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 1 row on the side of the top jaw and 3 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 do not have pectoral fins or scales. They are covered with thick yellow mucus, which provides them with protection from abrasion.

The Panamic Green Moray is found in shallow reef areas within cracks and crevices from the intertidal zone to depths of 100 m (330 feet). They reach a maximum of 1.50 m (4 feet 11 inches) in length. As of January 1, 2024, the International Game Fish Association world record stood at 4.76 kg (10 lbs 8 oz) with the fish caught in coastal waters of Costa Rica in December 2013. During the day they back into rocky crevices leaving only their head protruding. 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. The Panamic Green Moray is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.

The Panamic Green Moray Eel is a resident of all Mexican waters of the Pacific Ocean with the exception that they are absent from Guerrero Negro, Baja California, northward along the central and northwest coasts of Baja and from the extreme northern portion of the Sea of Cortez.

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).

From a conservation perspective the Panamic Green Moray is currently considered to be of Least Concern with stable, widely distributed populations. They are very seldom, seen by humans. When encountered they are visually most intimidating but are very timid and not harmful and are only known to bite humans on rare occasions. They are caught on occasion by recreational anglers out of heavy rock structure and normally a “catch and release”.