Lanternfishes: Myctophiformes

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LANTERNFISHES: Myctophiformes

SKINNYCHEEK LANTERNFISH (Benthosema pterotum): SPECIES ACCOUNT

PHYSICAL CHARACTERISTICS

Lanternfishes have many light-producing organs covering their bodies. These organs are arranged in patterns that vary according to species. In addition to light-producing organs, many lanternfishes have glowing scales and glands. Lanternfishes are small, about 3 inches (8 centimeters) long. The most common lanternfishes look like anchovies and sometimes are called glowing anchovies. The jaws of lanternfishes have many tiny teeth. These fishes have two general body types. One is a strong, firmly muscled body, and the other is a watery, flabby body with a weak skeleton and muscles.

Lanternfishes are brilliant metallic bronze to dark blue-black on the back and have mirrorlike silvery sides and belly. Some deep-dwelling lanternfishes are dark brown or black. The light-producing organs on freshly captured lanternfishes appear silver, reddish, or deep blue.

All lanternfishes have an adipose (ADD-uh-pohs) fin, which is a short fin between the dorsal fin and the tail fin. The dorsal (DOOR-suhl) fin is the fin along the midline of the back. Some species have long, sweeping pectoral (PECK-ter-uhl) fins, which are the front pair, corresponding to the front legs of four-footed animals. The pectoral fins of the flabby-bodied species are so small and delicate that they are almost unnoticeable. The rays, or supporting rods, of all lanternfish fins are soft.

GEOGRAPHIC RANGE

Lanternfishes live all over the world except the Arctic Ocean.

HABITAT

As adults most lanternfishes live in the middle depths of the open ocean, usually between 660 and 3,330 feet (200 and 1,000 meters). Some may enter the upper part of the deep-water region. Several lanternfishes are thought to live near, but not in contact with, the bottom at some point in life. Larval or young lanternfishes live near the surface, mainly between about 160 and 800 feet (50 to 250 meters).

DIET

Scientists do not know much about the feeding habits of lanternfishes. Some eat crustacean (krus-TAY-shun) plankton. Crustaceans are water-dwelling animals that have jointed legs and a hard shell but no backbone. Plankton are microscopic plants and, in this case, animals drifting in water.

BEHAVIOR AND REPRODUCTION

Little is known about the behavior of lanternfishes. They move from middle depths into very shallow surface waters at night to feed and to lay their eggs. These surface waters, usually above 330 feet (100 meters), are rich in food. The trips up and down take about two hours each, depending on conditions such as solar eclipses, the degree of moon fullness, the clearness of the night sky, and the presence of strong currents.

Swimming behavior among lanternfishes takes two forms depending on the body type. Strong-bodied species swim in short bursts, propelled by rapid closing of the tail fin rays and a flick of the tail. In general, these fishes are the strongest migrators and move around for food. The flabby-bodied forms tend to move with a slow eel-like wriggling of the entire body. These species usually live in the deeper middle zone of the ocean and travel shorter distances.

In warmer waters, lanternfishes spawn year-round. In cooler waters they spawn once a year. Warm-water species live one year or less, whereas cooler-water species may live three or four years.

LANTERNFISHES AND PEOPLE

Lanternfishes are processed to form fish meal, which is used as poultry feed and as crop fertilizer. Like sardines and anchovies, lanternfishes can be bought packed in oil. Lanternfishes are very important to the ocean environment. Damage to or loss of lanternfish populations would be harmful to many other animals in the food web of the open ocean.

CONSERVATION STATUS

Lanternfishes are not threatened or endangered.

SKINNYCHEEK LANTERNFISH (Benthosema pterotum): SPECIES ACCOUNT

Physical characteristics: Skinnycheek lanternfish have a large head and very large eyes. They are among the smaller lanternfishes, reaching a maximum length of about 2 inches (5 centimeters). These fish are mirrorlike silver on the sides and belly and blue-black on the back.

Geographic range: Skinnycheek lanternfish live in the northern Indian Ocean, the Arabian Sea, and the Pacific Ocean near Japan.

Habitat: Skinnycheek lanternfish live in open water in the middle depths of the ocean, near the continental shelf edges, and around islands.

Diet: Skinnycheek lanternfish eat crustacean plankton. As they grow larger, these fish eat larger crustaceans. They eat at night.

Behavior and reproduction: Skinnycheek lanternfish travel up and down in the water for feeding. They form extremely dense groups. In the northern Arabian Sea commercial open-water trawlers, or fishing boats using nets, have captured these fish at a rate of 88 tons (80 metric tons) per hour.

Female lanternfish can reproduce when they are about 1 inch (2.5 centimeters) long. The eggs are fertlized (FUR-teh-lyzed), or united with the male's sperm, outside the female's body. Spawning occurs in the late afternoon and evening as the fish are traveling upward. Skinnycheek lanternfish release two hundred to three thousand eggs per batch, depending on body size. They spawn from the time they reach sexual maturity until death. These fish live slightly less than one year.

Skinnycheek lanternfish and people: Skinnycheek lanternfish are processed for fertilizer.

Conservation status: Skinnycheek lanternfish are not threatened or endangered. ∎