GOBIES: Gobioidei

PHYSICAL CHARACTERISTICS

Gobies are small fishes with a body that is tubular or is narrow from side to side. Most are about 1½ to 4 inches (4 to 10 centimeters) long. Gobies have a short broad head that may be flat on top. The eyes are near the top of the head. There are usually two separate dorsal fins. The pectoral fins are broad and rounded but may be pointed in some species. Each pelvic fin has one spine. 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. The pectoral (PECK-ter-uhl) fins correspond to the front legs and the pelvic fins to the rear legs of four-footed animals. Some gobies have no scales, and some have them only on the rear part of the body. Some gobies are brightly colored, but others are brown or off white. In many gobies the pelvic fins are united to form a suction disk.

GEOGRAPHIC RANGE

Gobies live all over the world except the polar regions.

HABITAT

Most gobies live near the coast and in estuaries (EHS-chew-air-eez), or the areas where rivers meet the sea. About half of known species live in coral reefs. Some gobies live in caves, and some live in rivers and streams.

DIET

Gobies eat invertebrates (in-VER-teh-brehts), or animals without backbones. (Vertebrates are animals with backbones.) Some coral-dwelling gobies feed on the coral on which they live. Species that live in open water feed on plankton, or microscopic plants and animals drifting in water. Large gobies may feed on other, smaller fish. Some gobies scrape algae off rocks. Algae (AL-jee) are plantlike growths that live in water and have no true roots, stems, or leaves. Cleaner gobies pick parasites (PAIR-uh-sites) off other fishes. Parasites are animals or plants that live on other animals or plants without helping them and often harming them. Some gobies eat the tube feet of sea urchins.

BEHAVIOR AND REPRODUCTION

Some open-water species of gobies form schools. Many gobies are territorial, especially during the breeding season. Males often care for developing eggs. Females lay a few to several hundred small eggs, attaching them to the underside of rocks or onto plants or coral. The eggs usually hatch in a few days, and the young are dispersed by water currents. In freshwater species, the larvae (LAR-vee), or young, are swept downstream by the water current. The young spend a few weeks to months at sea before returning to freshwater.

SIZE COUNTS

The small size of gobies places them at risk from many predators. For example, gobies hiding under sea urchins are eaten by long-snouted predators that probe between the spines of the urchin, and shrimp can overpower small gobies.

WORLD'S SMALLEST

The stout infantfish, a goby 8.4 millimeters long and weighing 1 milligram, in July 2004 replaced the dwarf goby as the world's smallest fish and world's smallest vertebrate. Both fishes are smaller than a raisin but larger than a ladybug.

GOBIES AND PEOPLE

In some areas gobies are eaten by the local people. They also are used in aquariums.

CONSERVATION STATUS

The World Conservation Union (IUCN) lists five species of gobies as Critically Endangered, twenty-six as Vulnerable, one as Conservation Dependent, and twenty as Near Threatened. Critically Endangered means facing an extremely high risk of extinction in the wild. Vulnerable means facing a high risk of extinction in the wild. Conservation Dependent means if the conservation program were to end, the animal would be placed in one of the threatened categories. Near Threatened means at risk of becoming threatened with extinction in the future. The U.S. Fish and Wildlife Service lists one species as Endangered, or in danger of extinction throughout all or a significant portion of its range.

FIRE GOBY (Nemateleotris magnifica): SPECIES ACCOUNTS

Physical characteristics: Fire gobies reach a length of 3½ inches (9 centimeters). The front of the first dorsal fin is extremely long, almost as long as the fish itself. The second dorsal and the anal fins are long and look like the tail of an arrow. The head has a yellow mask over the snout and eyes. The front half of the fish is white, and the rear half goes from orange to red with green streaks.

Geographic range: Fire gobies live in the Indian and Pacific oceans.

Habitat: Fire gobies live on coral reefs over sand or gravel.

Diet: Fire gobies eat animal plankton.

Behavior and reproduction: Fire gobies hover, alone or in small groups, in the water just above the bottom. They usually have a small territory around a hole, cave, or burrow into which they retreat at the threat of danger. These fish flick their first dorsal spine up and down when threatened or defending territory. Mating occurs in burrows.

Fire gobies and people: Fire gobies are important saltwater aquarium species.

Conservation status: Fire gobies are not threatened or endangered. ∎

ATLANTIC MUDSKIPPER (Periophthalmus barbarus): SPECIES ACCOUNTS

Physical characteristics: Atlantic mudskippers grow to a length of about 6 inches (15 centimeters). Large eyes stick out of a large head. There are two dorsal fins. The body is tan but is lighter on the belly. There are black diagonal bars on the back and upper parts of the sides and pearly spots on the head and forward part of the trunk. A light edge on the first dorsal fin may be tinged with light blue. The second dorsal fin has a dark band over a light band.

Geographic range: Atlantic mudskippers live along the western coast of Africa.

Habitat: Atlantic mudskippers live near the seashore in mangrove estuaries and muddy tidal flats, where they live in burrows.

Diet: Atlantic mudskippers eat crustaceans, worms, and insects. Crustaceans (krus-TAY-shuns) live in water and have a soft segmented body covered by a hard shell.

Behavior and reproduction: Atlantic mudskippers use their muscular pectoral and pelvic fins for crawling and climbing. They flee from predators (PREH-duh-ters), or animals that hunt and kill other animals for food, by skipping or hopping across mudflats and into mangrove forests or into their burrows. On land, mudskippers keep a mouthful of water for extracting oxygen through the gills, and they can breathe through their skin. Spawning occurs in burrows.

Atlantic mudskippers and people: Atlantic mudskippers are not fished for food or sport. They are not widely used in aquariums.

Conservation status: Atlantic mudskippers are not threatened or endangered. ∎

MARBLE SLEEPER (Oxyeleotris marmorata): SPECIES ACCOUNTS

Physical characteristics: Marble sleepers are the largest gobies, reaching a length of about 35 inches (90 centimeters). These gobies have a streamlined body, a flat head, two dorsal fins, and a rounded tail fin. The body is brown with dark blotches.

Geographic range: Marble sleepers live in Southeast Asia. They have been introduced into Taiwan for fish farming.

Habitat: Marble sleepers live in rivers, lakes, swamps, ditches, and ponds over muddy, sandy, or gravel bottoms. These fish also may be found in water with a low salt content around the mouths of rivers and canals.

Diet: Marble sleepers eat small fishes and invertebrates.

Behavior and reproduction: Marble sleepers live alone and are active at night, prowling slow-moving streams, lakes, and swamps. During the day these fish rest at the bottom, taking cover among rocks and plants. Marble sleepers are able to reproduce when they are about 4 inches (10 centimeters) long. The males care for the eggs and guard the newly hatched young. The larvae drift freely at first but become bottom dwellers about twenty-five to thirty days after hatching.

Marble sleepers and people: Marble sleeper is a highly prized food fish in Southeast Asia, where it is also raised in ponds.

Conservation status: Marble sleepers are not threatened or endangered. ∎

FOR MORE INFORMATION

Books:

Ferrari, Andrea, and Antonella Ferrari. Reef Life. Buffalo, NY: Firefly, 2002.

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

Web sites:

Lee, H.J., and Jeffrey B. Graham. "Their Game Is Mud." Natural History.http://www.naturalhistorymag.com/0902/0902_feature.html (accessed on November 1, 2004).

"Stout Infantfish: Schindleria brevipinguis, Watson & Walker, 2004." Australian Museum Fish Site. http://www.amonline.net.au/fishes/fishfacts/fish/sbrevip.htm (accessed on November 1, 2004).