Clingfishes and Singleslits: Gobiesocoidei

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Instead of pelvic fins, or the pair that corresponds to the rear legs of four-footed animals, clingfishes have a sucking disk they use to cling to rocks, plants, and even sea urchins. Most clingfishes have a tadpole-shaped body, but one species has a long, thin body that mimics the long spines of a sea urchin. Clingfishes have no scales but shield themselves with mucus. They also have no swim bladder, an internal sac that fishes use to control their position in the water. The colors of clingfishes vary from black to orange, brown, green, or red. The fishes also may have stripes, bars, or spots of yellow, blue, green, brown, gray, or white. Most clingfishes are about 2 inches (5 centimeters) long, but some reach a length of 12 inches (30 centimeters). Clingfishes have one dorsal and one anal fin. The dorsal (DOOR-suhl) fin is the one along the midline of the back. The anal (AY-nuhl) fin is the one along the midline of the belly.

Singleslits have an eel-like shape. The pelvic fins are very small. These fishes have a sucking disk, but it does not function. The dorsal and anal fins look like those of eels. Only the tail fin has rays, or supporting rods. The colors vary from frosty pink or green to light green, brown, gray, or black. Spots or bars of black, gray, brown, or yellow may be present. Singleslits are usually smaller than 2 inches (5 centimeters) long, but one species reaches a length of 5 inches (12 centimeters).


Clingfishes live in the Atlantic, Indian and Pacific oceans. Singleslits live off the southern coast of Australia.


Clingfishes cling to the bottom. They can withstand breaking waves and surging waters. Many species live on or under boulders and rocks, in crevices, and on rocky slopes and rock faces. Species that live in tide pools can stay out of water for several days, if they stay moist and out of sunlight. Some species live with coral, sponges, sea squirts, and sea urchins. Others cling to the blades of sea grasses and seaweed. Singleslits live in the sea near the shore, usually in shallow tide pools and often under stones or in seaweed.


Clingfishes eat algae, body parts of sea urchins, small fishes, and small invertebrates (in-VER-teh-brehts), or are animals without backbones. Some are cleaner fishes that remove parasites from other fishes. Singleslits feed mainly on small, bottom-dwelling invertebrates. Algae (AL-jee) are plantlike growths that live in water and have no true roots, stems, or leaves. Parasites (PAIR-uh-sites) are animals or plants that live on other animals or plants without helping them and often harming them.


Clingfishes use their sucking disk to cling to rocks, plants, or even sea urchins. Clingfishes and singleslits tend to be secretive and probably are territorial. In mating the male nudges the female's belly. If the female accepts him, the male moves parallel to her and quivers. The female then quivers and deposits eggs on stones, algae, or other bottom material while the male places sperm on them. Egg laying may last several minutes to a few hours. The eggs then are guarded by the male or abandoned by the pair. Larvae (LAR-vee), the early stage that must change form before becoming adults, probably drift in the water.


Some clingfishes and singleslits are collected for aquariums.


Clingfishes and singleslits are not threatened or endangered.


Physical characteristics: Sonora clingfish have a long thin body with a broad head and a large sucking disk. There are light diagonal stripes along the entire body and a pair of spots just behind the head. Sonora clingfish grow to a length of about 3 inches (8 centimeters).

Geographic range: Sonora clingfish live in the Gulf of California, off Mexico.

Habitat: Sonora clingfish live under rocks, to which they cling, and in little or no water. If kept moist, these fish can withstand extreme temperatures when exposed to air.

Diet: Sonora clingfish hunt during the day for small crustaceans and mollusks, such as barnacles and limpets. Crustaceans (krus-TAY-shuns) are water-dwelling animals that have jointed legs and a hard shell but no backbone. Mollusks (MAH-lusks) are animals with a soft, unsegmented body that may or may not have a shell.

Behavior and reproduction: Sonora clingfish are secretive, clinging to the undersides of rocks and moving over rocky surfaces to feed. Their movements are related to tidal movements. Activity is greater at high tide, and there is little or no activity at low tide. Males are territorial. Both males and females produce large amounts of mucus, which coats their bodies and protects the fish from drying out.

Sonora clingfish form pairs to mate at the bottom of their habitat. A single male may mate with more than one female. Eggs are sticky and are laid on the underside of rocks, where they are guarded by the male, sometimes with the aid of one or more females. During low tide, the parents secrete mucus that protects the eggs from exposure. The larvae drift in the water.

Sonora clingfish and people: Sonora clingfish sometimes are collected for aquariums.

Conservation status: Sonora clingfish are not threatened or endangered. ∎



Gilbert, Carter Rowell, and James D. Williams. National Audubon Society Field Guide to Fishes: North America. New York: Knopf, 2002.

Web sites:

"Eastern Cleaner-Clingfish: Cochleoceps orientalis Hutchins, 1991." Australian Museum Fish Site. (accessed on October 31, 2004).

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Clingfishes and Singleslits: Gobiesocoidei

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