Bridled Goby, Coryphopterus glaucophraenum
Bridled Goby, Coryphopterus glaucophraenum. Underwater photographs taken in coastal waters off Bonaire, December 2019. Photographs and identifications courtesy of Bob Hillis, Ivins, Utah.
The Bridled Goby, Coryphopterus glaucophraenum, is a member of the Goby or Gobiidae Family, and is also known as the Bridled Sand Goby and in Mexico as gobio de riendas. Globally, there are sixteen species in the genus Coryphopterus of which eight are found in Mexican waters, seven in the Atlantic and one in the Pacific Ocean.
The Bridled Goby has an elongated body with a slightly rounded snout that has a small horizontal mouth. They are translucent in color and their head has a black spots on top. They are characterized by “X”-shaped marks on their sides mid-body. They have a white line under their eyes, a prominent double-pointed triangular black spot above the corner of the gill cover, a small dark spot on the upper pectoral base and the caudal base has 2 dark spots. Their fins are transparent. Their anal fin has 1 spine and 9 or 10 rays; their first dorsal fin has 6 spines; their second dorsal fin has 10 rays; their pectoral fins have 17 to 20 rays; and, their pelvic fins have 1 spine and 5 rays that are fused into a sucking disc. Their body is covered with large rough scales. They do not have a lateral line.
The Bridled Goby is found in clear white sandy areas near deep reefs and grassy and rocky areas, inshore in murky waters and within mangroves at depths up to 45 m (145 feet) in water temperatures between 22oC (73oF) and 31oC (89oF). They reach a maximum of 8.0 cm (3.1 inches) in length. They have a small home range and are highly territorial. They are very active diurnally and feed by sand filtering on sand dwelling invertebrates. They utilize crevices in the reef and can burrow in sand as means of protection against predation. Reproduction involves sequential protogynous hermaphrodites with juveniles maturing into Initial Phase (IP) females and then transitioning midlife to terminal phase (TP) males. Both males and females breed with multiple partners. They are oviparous with females laying their eggs on hard surfaces which are then fertilized and guarded by the males. Their larvae are pelagic and mature within sixty days and can be sexually active within three weeks. They are of scientific interest due to their extreme bipartite life-history strategy: a relatively slow-growing pelagic larval stage, delayed metamorphosis, in combination with a rapidly maturing and high-mortality of adults. They have life spans of three years.
The Bridled Goby is easily confused with the Colon Goby, Coryphopterus dicrus, the Patch Reef Goby, Coryphopterus tortugae and the Sand Canyon Goby, Coryphopterus boi, but all lack the”X”-shaped marks on their sides.
The Bridled Goby is a resident of all Mexican waters of the Atlantic Ocean including the Gulf of Mexico, with the exception that they are absent north of Tuxpan, Veracruz, and the east coast of the Yucatán Peninsula in the Caribbean.
From a conservation perspective the Bridled Goby is currently considered to be of Least Concern with stable, widely distributed populations. Their long-term viability is threatened by recently introduced invasive species such as the Red Lionfish, Pterois volitans, and the continuing destruction of coral reefs, their native habitat. They are small in stature and are of little interest to most. They are utilized by the aquarium trade on a limited basis due to their tranquil nature but require a high level of attention including frequent feedings.