Bathygobius mystacium

Common Name

Island Frillfin Goby

Year Described

Ginsburg, 1947


Dorsal Fin: VI, I-9
Anal Fin: I, 8
Pectoral Fin: 17-20
Caudal Rays: 17 upper, 15 lower lobe (all types)
Scale Rows: 33-36
Pre-dorsal Scales: 17-20

Body of typical shape for the gobies but robust. Eye medium sized; larger than snout length. Upper jaw usually less than 11% of SL (9.2-11.0% SL). Pectoral fin extends to rear margin of first dorsal. Upper 4 pectoral rays (rarely 3 or 5) separate from membrane; bifurcated. Pelvic fins fully fused into disk. Pelvic fins just reach anus. Caudal fin rounded. Body fully scaled with scales extending forward of level of pre-opercular margin.


Body pale brown with longitudinal darker yellow-brown stripes that follow scale rows. Head and body mottled with ~3 irregular black saddles dorsally. A single row of 6 large black blotches along lower side that are a little smaller than eye. Blotches do not form a checkerboard or regular pattern. First dorsal fin with two longitudinal dark stripes and a yellowish tip. Second dorsal and caudal fin with brown spots and a yellowish margin. Lower fins pale with dusky margins. Pectoral fin yellowish. Eye dark.


Maximum size to 57mm SL.


Shallow coastal waters, including intertidal pools, rocky beds on calm shorelines, patch reefs, seagrass beds, and in mangrove lagoons. Can occur over hard or soft bottoms. More common on exposed shorelines.


Scattered records in the Caribbean islands (Bahamas, Cuba, Caymans, Puerto Rico, Curacao and Belize).


Lima-Filho, P.A., R. de Souza Rosa, A.D.S. de Souza, G.W.W.F. da Costa, C. de Oliveira, & W.F. Molina. 2016. Evolutionary diversification of Western Atlantic Bathygobius species based on cytogenetic, morphologic and DNA barcode data. Reviews in Fish Biology and Fisheries: 26(1), 109-121.

Tornabene, L., C. Baldwin, L.A. Weigt, and F. Pezold. 2010. Exploring the diversity of western Atlantic Bathygobius (Teleostei: Gobiidae) with cytochrome c oxidase-I, with descriptions of two new species. Aqua: 16(4), 141-170.

Tornabene, L. and F. Pezold. 2011. Phylogenetic analysis of Western Atlantic Bathygobius (Teleostei: Gobiidae). Zootaxa: 3042, 27-36.

Other Notes

A unique clade distinct from the antilliensis/geminatus and lacertus/soporator clades, according to Tornabene et al., 2010.