Common names: frillfin (English), gobio (Espanol), mapo (Espanol)
Bathygobius andrei (Sauvage, 1880)
Body robust; head broad, depressed; snout bluntly rounded; eyes large, close together; mouth moderate sized, relatively horizontal; tongue with distinct notch in front; jaw teeth in bands, without canines; dorsal fins VI + I, 9-10 rays; anal I, 8-9 rays; pelvic disc more or less rounded, its front membrane with angular edges; tail round, 23-32 rays; pectoral rays 20-22, the uppermost 6 rays forming free filaments, 1st to 4th branch only once; scales large, rough, 33-36 on mid side, predorsal scales not reaching eyes; sometimes a small patch of scales on upper corner of operculum, rest of head scaleless.
Grey brown with light streak on each scale; faint dark bars and blotches evident on side; head without pale spots; 1st dorsal fin with an oblique dark bar at front; 3 dark blotches behind eye small, 2nd is smallest and 3rd is largest; juveniles are much lighter with well defined blackish bars and blotches and a dark-spotted caudal fin.
Size: grows to at about 15 cm.
Inhabits brackish water in tide pools and rocky shores of bays and in creeks and estuaries.
Depth: 0-2 m.
Guatemala to northern Peru.