Butterfishes and Relatives: Stromateoidei
BUTTERFISHES AND RELATIVES: StromateoideiBUTTERFISH (Peprilus triacanthus): SPECIES ACCOUNT
Butterfishes and their relatives have large eyes, a small mouth, a forked tail fin, and a long dorsal fin. Between the gills and the esophagus, most of these fishes have a sac used for breaking down food. The inside of the sac is coated with tiny teeth. The body of butterfishes and their relatives is tapered at the ends and is either narrow from side to side or rounded in cross-section. These fishes reach a length of about 4 feet (1.2 meters). The scales usually are smooth. The color of adults varies from silver to dark brown, but young butterfishes usually have mottled colors. The dorsal and anal fins have spines. The pelvic fins are absent in some species, small in others, and large in others. 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 pelvic fins correspond to the rear legs of four-footed animals.
Butterfishes and their relatives live in the Atlantic, Pacific, and Indian oceans.
Butterfishes and their relatives live in the ocean well offshore, close to the shore, or in large bays. Adults live in deeper waters, either on the bottom or in open water in middle depths. The young usually live near the surface, sometimes among jellyfishes.
Butterfishes and their relatives mostly eat invertebrates (in-VER-teh-brehts), or animals without a backbone. Some species eat small fish.
BEHAVIOR AND REPRODUCTION
Scientists know little about the behavior of butterfishes and their relatives other than that some of these fishes live among jellyfishes. Many species form schools. Some gather under floating wreckage and buoys and around boats. Butterfishes and their relatives release large numbers of eggs into open water. These fishes probably spawn once a year.
BUTTERFISHES AND THEIR RELATIVES AND PEOPLE
Butterfishes and their relatives are caught and sold for food in some areas, especially Japan and Southeast Asia.
Young butterfish are more resistant to jellyfish poison than are other fishes. The butterfish hovers under the bell of the jellyfish but may swim in and out of the tentacles to snatch food. The butterfish also sometimes feeds on the tentacles and sex organs of the jellyfish. Sometimes the jellyfish eats the butterfish.
Butterfish are named for their melt-in-your-mouth flavor.
Butterfishes and their relatives are not threatened or endangered.
Physical characteristics: Butterfish are about 12 inches (30 centimeters) long. The body is narrow from side to side and broad from back to belly. The single long dorsal and anal fins are tall and pointed near the front and taper toward the rear. The pectoral (PECK-ter-uhl) fins, the pair that corresponds to the front legs of four-footed animals, are long. The tail fin is deeply forked. There are no pelvic fins. The fish's back is grayish blue. The sides are silver with dark spots.
Habitat: Butterfish live in open water or on the bottom, usually over sand. They may enter shallow bays and estuaries (EHS-chew-air-eez), or the areas where rivers meet the sea.
Diet: Butterfish eat sea squirts, mollusks, and small crustaceans. Mollusks (MAH-lusks) are animals with a soft, unsegmented body that may or may not have a shell. Crustaceans (krus-TAY-shuns) are water-dwelling animals that have jointed legs and a hard shell but no backbone.
Behavior and reproduction: Butterfish are active day and night. During their first year these fish may live among jellyfishes or freely, but they form schools as adults. Butterfish can reproduce when they are one or two years old. They spawn once a year, scattering their eggs, which drift in open water.
Butterfish and people: Butterfish are important food fish.
Conservation status: Butterfish are not threatened or endangered. ∎
FOR MORE INFORMATION
Schultz, Ken. Ken Schultz's Field Guide to Saltwater Fish. New York: Wiley, 2004.
"Butterfish: Poronotus triacanthus (Peck) 1800." Fishes of the Gulf of Maine. http://gma.org/fogm/Poronotus_triacanthus.htm (accessed on February 11, 2005).