Hawaii's Reef Fishes

Gobies

Cocos Frill Goby Bathygobius cocosensis (Bleeker, 1854)

The Gobiidae is the largest family of marine fishes in the world, and there are many subspecies that live in freshwater environments.

About 1,875 species are known; still more remain to be described. Although the third largest family of fishes in Hawaii, with 28 marine species, it is poorly represented compared to other areas of the lndo-Pacific. This is probably due to the relatively short larval life of most species.

The majority of gobies are small, most less than 10 cm in length [and a few as small as 0.4 inches (1 cm) as adults—the smallest fishes in the world]. The pelvic fins of gobies are close together and usually fused to form a sucking disk.

Nearly all the species have 2 dorsal fins, the first often with 6 spines; most have a rounded caudal fin. Scales are present on the body of most species, but a few lack scales; there is no lateral line. The opercle is without a spine.

Gobies are primarily shallow-water species; all are carnivorous and bottom-dwelling. Some occur only in tidepools or on very shallow sand or mud flats, hence they are not often seen by snorkelers or divers; examples are the frill gobies of the genus Bathygobius of which three occur in Hawaii.

Most gobies rest directly on the substratum, but some hover a short distance above. Gobies are associated with a variety of habitats such as coral reef, sand, mud, rubble, or seagrass. Many live in close association with other animals such as sponges, gorgonians, and snapping shrimps.

Nearly all gobies for which the reproductive habits are known lay demersal eggs which are guarded by the male parent. A few have been shown to be protogynous hermaphrodites (begin mature life as females and change sex later to males). The general Hawaiian name for gobies is ‘o’opu.

Whip-Coral Goby

Brianinops yongei (Davis & Cohen, 1968)

Transparent dorsally with 7 narrow yellowish brown bars that link to ventral dusky yellowish brown half of body; an internal pale yellowish to whitish line above vertebral column; dorsal spines usually 6, soft rays 8-9; pectoral rays usually 15-16, all but lower 3-6 branched; scales about 40.

Attains 1.5 inches (3.5 cm). Indo-Pacific; usually found on the antipatharian seawhip Cirrhipathes anguina.

Cocos Frill Goby

Bathygobius cocosensis (Bleeker, 1854) 'o'opu ohune

Light gray-brown with broad dark bars on the back and elliptical black spots alternating with smaller spots in a row on lower side of body; dorsal fins usually 6 spines, 9 soft rays; pectoral rays 18-20, the upper 3 or 4 free of membrane; predorsal scales to above preopercular margin. To 3.2 inches (8.2 cm). Indo-Pacific; common in tidepools and shallow silty flats.

All information and pictures in this section are from John E. Randall's Shore Fishes of Hawai'i by permission of the author.