River Goby

River Goby, Awaous banana

The River Goby, Awaous banana, whose Spanish common name is gobio de río, is a species in the Goby or Gobiidae Family, known collectively as gobios in Mexico. Globally, there are thirteen species in the genus Awaous, one of which is found in Mexican waters, this species which is found both in the Atlantic and the Pacific.

The River Gobies have robust elongated rounded bodies with a flat ventral side. They have an overall tan to brown coloration that transitions to pale yellow and white ventrally. Their head has three black slanted bars and their body has seven irregular black bars on the upper sides; the first bar extends from above the gill cover onto the pectoral fin and the bar under the origin of the dorsal fin is crescent-shaped. Their flanks have 7 or 8 black blotches and their back has a series of irregular small spots. Their anal and pelvic fins are pinkish; their caudal fin has 7 or 8 dark bars; their dorsal fin is yellowish; and their pectoral fin has a black bar at the front and its base is pinkish-orange. Their head is depressed and broader than it is deep and has a blunt snout, a moderately-sized inferior mouth with large fleshy lips, and small eyes set very close together on top of the head. Their caudal fin is rounded; their first dorsal fin has 6 spines; their second dorsal fin has one spine and 9 to 12 rays; and their pelvic fins are fused into a disk (pictured below). They do not have a lateral line and are covered with large rough scales.

The River Gobies are found in clear streams and rivers over sand and gravel at depths up to 10 feet. They reach a maximum length of 37 cm (15 inches). They consume aquatic insects, foraminifers, and plant materials. They spawn in the ocean, with the larvae being pelagic and becoming widely dispersed. Juveniles quickly return to fresh water; adults and juveniles spend most of their time in fresh to brackish water. They prefer water temperatures between 25°C (77°F) and 30°C (86°F). The River Gobies are a shallow-water, poorly studied species and very little is known about their behavioral patterns.

In Mexican waters the River Gobies are found in all freshwater rivers of the Atlantic and the Pacific with the exception that they are absent from northwest coast of Baja and from the northern half of the Sea of Cortez.

The River Goby is not easily confused with any other species from the Atlantic. In the Pacific it is fairly similar in appearance and might be confused with the Cheekspot Goby, Ilypnus gilberti (black chin; anal fin with dark stripe), the Guaymas Goby, Quietula guaymasiae (uniform gray color), the Longjaw Mudsucker, Gillichthys mirabilis (rows of dark blotches on flanks), and the Shadow Goby, Quietula y-cauda (rows of dark spots on flanks).

The River Gobies are a target of subsistence fishermen in the greater San José area during rare breaches in the dyke separating the San José River from the Sea of Cortez, however, they are of limited interest to most.

River Goby, Awaous banana. Fish collected at the mouth of the San José River, Baja California Sur, July 2005, by locals using a cast net, during a breach in the barrier caused by Hurricane Hilary. Length: 10.5 cm (4.5 inches)River Goby, Awaous banana. Fish collected at the mouth of the San José River, Baja California Sur, July 2005, by locals using a cast net, during a breach in the barrier caused by Hurricane Hilary. Length: 22.0 cm (8.7 inches). Note the extensive elongation of the snout in this larger fish.