Frillfin Goby, Bathygobius soporator

Frillfin Goby, Bathygobius soporator, Breeding Male. Fish caught off the beach at Playa del Carmen, Yucatán, Quintana Roo, February 2016. Length: 4.6 cm (1.8 inches). Catch, photograph and identification courtesy of George Brinkman, Guelph, Ontario, Canada.

Frillfin Goby, Bathygobius soporator. Fish caught off the beach at Playa del Carmen, Yucatán, Quintana Roo, February 2016. Length: 5.8 cm (2.3 inches). Catch, photograph and identification courtesy of George Brinkman, Guelph, Ontario, Canada.

Frillfin Goby, Bathygobius soporator. Fish caught from coastal waters off Sebastian, Florida, March 2021. Length: 11.2 cm (4.4 inches). Catch, photograph and identification courtesy of Ben Cantrell, Sebastian, Florida.

Frillfin Goby, Bathygobius soporator. Fish caught from coastal waters off Sebastian, Florida, March 2021. Length: 11.2 cm (4.4 inches). Catch, photograph, and identification courtesy of Josh Leisen (joshadventures.com), Gaylord, Michigan.

Frillfin Goby, Bathygobius soporator. Fish caught from coastal waters off Fish caught from coastal waters off Caye Ambergris, Belize, June 2013. Length: 12.7 cm (5.0 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).

The Frillfin Goby, Bathygobius soporator, is a member of the Goby or Gobiidae Family, and is known in Mexico as mapo aguado. Globally, there are twenty-seven species in the genus Bathygobius, of which five are found in Mexican waters, four in the Atlantic and one in the Pacific Ocean.

The Frillfin Goby has an elongated rounded body. They are grayish brown with the upper half of their body having three prominent dark saddles often connected to 6 or 7 large dark irregular blotches. Their caudal fin has a large dark blotch at the base and thin dark bars on the outer half. Their first dorsal fin has a broad diagonal or vertical dark bar and their second dorsal fin has thin dark stripes and a yellowish outer edge. Their head is broad with a rounded blunt snout, a moderately-sized mouth, and large eyes set very close together. Their anal fin has 1 spine and 8 rays; their caudal fin is rounded; their first dorsal fin has 6 spines; their second dorsal fin has 1 spine and 9 rays; their pectoral fins have 20 rays, the first 3 to 5 being free-standing; and, their pelvic fins are close together on the belly. Their body is covered with large rough scales. Their lateral line is only present on their head.

The Frillfin Goby is a tidal pool resident found in sheltered and rocky habitats in and around mixed sand bottoms at depths up to 3 m (10 feet). They are also found in turtle grass beds with rocks and mangroves and at the mouth of fresh water streams. They reach a maximum of 15.0 cm (5.9 inches) in length. They feed primarily on algae. The Frillfin 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 Frillfin 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 Frillfin Goby is similar in appearance and can be confused with the Island Frillfin, Bathygobius mystacium (3 dark saddles dorsally and 6 square blotches ventrally), the Notchtongue Goby, Bathygobius curacao (uniform body color without blotches), and the Twinspotted Frillfin, Bathygobius geminatus (two offset rows of blotches on lower sides of body).

From a conservation perspective the Frillfin Goby is currently considered to be of Least Concern with stable, widely distributed populations. Due to their small size they are of limited interest to most.