Darter Goby, Ctenogobius boleosoma
Darter Goby, Ctenogobius boleosoma. Fish caught from a lagoon of Flagler Beach, Florida, December 2022. Length: 6.6 cm (2.6 inches). Catch, photograph and identification courtesy of Ben Cantrell, Sebastian, Florida.
Darter Goby, Ctenogobius boleosoma. Fish caught from coastal waters off Long Island, New York, September 2023. Length: 6.8 cm (2.7 inches). Catch, photograph and identification courtesy of Aidan Perkins, Long Island, New York.
The Darter Goby, Ctenogobius boleosoma, is a member of the Goby or Gobiidae Family, that is also known at the American Freshwater Goby and in Mexico as Esmeralda flechera and madrejuile. Globally, there are twenty-eight species in the genus Ctenogobius, seven of which are found in Mexican waters, five in the Atlantic and two in the Pacific Ocean.
The Darter Goby has an elongated compressed body. They have five rounded or elongated black blotches on the sides that merge with V-shaped saddles under the second dorsal fin and a blackish oval above the pectoral fin base and a large black spot on the caudal fin base. The caudal fin has a black spot at the base that is more prominent in males (males also have a red stripe at the margin); the first dorsal fin has diagonal bars, and the second dorsal fin is diagonally barred with dark spots at the tip in males. They have a rounded head with large eyes that are set close together and near the front. Their mouth is equipped with several rows of teeth and 3 canines on the top jaw and several rows of teeth on the lower jaw. They have 4 or 5 short triangular gill rakers. Their anal fin has 1 spine and 10 to 12 rays; their first dorsal fin has 6 spines, and their second dorsal fin has 1 spine and 9 to 11 rays; the pectoral fins have 12 to 19 rays; and, their pelvic fins have 1 spine and 5 rays that form a disc. The body is covered with scales. They do not have a lateral line.
The Darter Goby is found in tranquil brackish and freshwater bodies and in low salinity upper estuarine marshes in grassy and sandy and muddy areas and occasionally in open bays and sounds at depths up to 10 m (33 feet) with water temperatures between 11oC (52oF) and 31oC (88oF). They are amphidromous migrating between fresh and saltwater environments but not to spawn. They are euryhaline being able to tolerate salinities up to 25.9 ppt and are capable of breathing air. They reach a maximum of 10.5 cm (4.1 inches). They are an omnivore that primarily consume ostracods. Reproduction is oviparous. The Darter Goby 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 Darter Goby is a resident of all Mexican waters of the Atlantic Ocean including the Gulf of Mexico and the east coast of the Yucatán Peninsula in the Caribbean.
The Darter Goby is similar in stature and can be confused with the Dash Goby, Ctenogobius saepepallens (dark dashes on the sides), the Freshwater Goby, Ctenogobius shufeldti (rectangular blotches on the sides), and the Mexican Goby, Ctenogobius claytonii (five narrow bars on the sides that are not V-shaped).
From a conservation perspective the Darter Goby is currently considered to be of Least Concern with stable, widely distributed populations. They are very small in stature and of limited interest to most. Their long-term viability is threatened by human coastal development.