Appearance
The black goby is deeper-bodied than the common goby, sand goby and two-spotted goby with a more rounded snout and generally a larger size. It has two dorsal fins that are almost continuous, the anterior one having six spines, which may project from the fin membrane, and the posterior and shorter one having soft rays. The posterior dorsal fin terminates close to the caudal peduncle in contrast to the common and sand gobies where there is a long gap. The pelvic fins are fused. The colour is some shade of dark brown with indistinct black blotches. The colour of the male becomes almost black during the breeding season and his fins become more vivid. The average size of this fish is about 5 to 7 cm (2.0 to 2.8 in)

