Frillfin Goby

Frillfin Goby, Bathygobius soporator

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

The Frillfin Gobies have robust elongated rounded bodies. They are grayish brown with the upper half of their body having three prominent dark saddles often connected to six or seven 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 caudal fin is rounded; their first dorsal fin has 6 spines; their second dorsal fin has one 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. They do not have a lateral line and with the exception of the head, their body is covered with large rough scales.

The Frillfin Gobies are tidal pool residents found in sheltered and rocky habitats in and around mixed sand bottoms at depths up to ten 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 length of 15.0 cm (5.9 inches). They feed primarily on algae. They are a small, shallow-water species and very little is known about their behavioral patterns.

In Mexican waters the Frillfin Gobies are found in all waters of the Atlantic.

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).

Due to their small size, the Frillfin Gobies are of limited interest to most.

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, photo 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, photo and identification courtesy of George Brinkman, Guelph, Ontario, Canada.

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f495-frillfin-goby-7Frillfin Goby, Bathygobius soporator. Fish caught from coastal waters off Spanish Harbor Key, Florida, December 2014. Length: 9.4 cm (3.7 inches). Catch, photo and identification courtesy of Ben Cantrell, Peoria, IL.

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f495-frillfin-goby-5Frillfin Goby, Bathygobius soporator. Fish caught from coastal waters off Spanish Harbor Key, Florida, December 2014. Length: 10.3 cm (4.1 inches). Catch, photo and identification courtesy of Ben Cantrell, Peoria, IL.

Frillfin Goby, Bathygobius soporator. Fish caught from coastal waters off Sugarloaf Key, Florida, April 2017. Length: 12.8 cm (5.0 inches). Catch, photo and identification courtesy of Dean Kimberly, Atlanta, GA.

Frillfin Goby, Bathygobius soporator. Fish caught from coastal waters off Sugarloaf Key, Florida, August 2014. Length: 13.0 cm (5.1 inches). Catch, photo and identification courtesy of Dean Kimberly, Atlanta, GA. Identification reconfirmed courtesy of Dr. Phil Hastings, Scripps Institution of Oceanography, La Jolla, CA.