Milkfish and Relatives: Gonorynchiformes - PHYSICAL CHARACTERISTICS, GEOGRAPHIC RANGE, HABITAT, DIET, BEHAVIOR AND REPRODUCTION, MILKFISH AND THEIR RELATIVES AND PEOPLE
Milkfish are large, silver, and tapered at the ends. Of their relatives, sandfish are slender and ribbon shaped; African mudfish are tubular; and Kneria wittei, which has no common name, are tiny and minnow-like. The length of these fishes ranges from about three-fourths inch (1.8 centimeters) to 5 feet (1.5 meters).
Milkfish and their relatives live all over the world except Antarctica.
Milkfish and their relatives live in saltwater and freshwater. Milkfish live in the open ocean but breed near the shore. Sandfish live in sandy areas along the coast or on the ocean bottom. Kneria wittei live in ponds or fast-moving streams or waterfalls. African mudfish live in quiet, shaded waters and can breathe air.
Milkfish and their relatives eat crustaceans (krus-TAY-shuns), water-dwelling animals that have jointed legs and a hard shell but no backbone; plankton, microscopic plants and animals drifting in bodies of water; plants; and algae (AL-jee), which are tiny plantlike growths that live in water and have no true roots, stems, or leaves.
BEHAVIOR AND REPRODUCTION
Milkfish form schools, both when they are young and as adults. Sandfish and African mudfish are solitary. All milkfish and their relatives use external fertilization (FUR-teh-lih-zay-shun), meaning eggs are released by the female, join with the male's sperm, and hatch outside the body.
MILKFISH AND THEIR RELATIVES AND PEOPLE
The milkfish is used for food.
Milkfish and their relatives are not threatened or endangered.
Physical characteristics: Milkfish can reach a length of about 6 feet (1.8 meters) but usually are about 5 feet (1.5 meters) long. Adults are silvery and have a forked tail, large eyes, and a pointed snout. They have a special pouch in the digestive tract for sifting plankton. The jaws are toothless. The dorsal (DOOR-suhl) fin, the one along the midline of the back, has thirteen to seventeen rays, or supporting rods; the anal (AY-nuhl) fin, the one along the midline of the belly, has six to eight rays; the pectoral (PECK-ter-uhl) fins, the front pair, have fifteen to seventeen rays; and the pelvic fins, the rear pair, have ten or eleven rays. Four or five rays support the gill covering on each side behind the head.
Geographic range: Milkfish live throughout the Indian and Pacific oceans.
Habitat: Adult milkfish live in the open ocean. Larvae (LAR-vee), or the early stage that must change form before becoming an adult, live in inland ponds that have a salt content slightly less than that of seawater.
Diet: Milkfish larvae eat animal plankton. Adults eat bacteria, algae, small bottom-dwelling invertebrates (in-VER-teh-brehts), which are animals without backbones, and sometimes eat free-floating fish eggs and larvae.
Behavior and reproduction: Milkfish, both young and adults, are schooling fishes. They breed near the shore and release their eggs into open water. When the larvae are about three-eighths inch (1 centimeter) long, they enter water that has a slightly lower salt content than seawater. The young adults return to the sea.
Milkfish and people: Milkfish is one of the most important food fishes in Indonesia, the Philippines, and Taiwan. It is commercially farmed in these areas. The young are caught close to shore and then raised in coastal ponds. Milkfish also is fished extensively throughout its range. Fishermen use cormorants with rings around the birds' necks to catch the fish. The rings prevent the birds from fully swallowing the fish.
Conservation status: Milkfish are not threatened nor endangered. ∎
FOR MORE INFORMATION
Ricciuti, Edward R. Fish. Woodbridge, CT: Blackbirch, 1993.
Schultz, Ken. Ken Schultz's Field Guide to Saltwater Fish. New York: Wiley, 2004.
"Milkfish." All Science Fair Projects. http://www.all-science-fair-projects.com/science_fair_projects_encyclopedia/Milkfish (accessed on September 23, 2004).
"Milkfish." SEAFDEC Aquaculture Department. http://www.seafdec.org.ph/home.html (accessed on September 24, 2004).
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