SALMONS: Salmoniformes

PHYSICAL CHARACTERISTICS

The salmon group includes salmons, trouts, whitefishes, and graylings. These fishes can be more than 5 feet (1.5 meters) long and weigh more than 100 pounds (45 kilograms). Salmons have streamlined bodies that are covered with small, smooth scales. Salmons have a small adipose (AE-dih-POS) fin between the dorsal (DOOR-suhl) fin, or the fin along the midline of the back, and the powerful tail fin.

GEOGRAPHIC RANGE

Salmons live in the Northern Hemisphere.

HABITAT

Many salmons spawn, or release eggs, in freshwater and migrate (MY-grayt), or move, to the sea to mature. Some salmons spawn near the ocean shore and have no real freshwater phase. Others never leave freshwater.

DIET

Some salmons eat plankton, or microscopic plants and animals drifting in bodies of water, and bottom-dwelling invertebrates (in-VER-teh-brehts), which are animals without a backbone. Other salmons eat other fishes.

BEHAVIOR AND REPRODUCTION

Some salmons are fiercely territorial and protect their living or breeding area. Others form schools soon after hatching and start their trip to the sea. The most remarkable characteristic of salmons is their strong swimming ability. Some can leap over obstacles, such as waterfalls, as high as 10 feet (3 meters). Salmons also are famous for returning to the stream of their birth after migrating thousands of miles in the ocean for one or more years. Salmons lay eggs that are fertilized (FUR-teh-lyezd), or penetrated by sperm to start development, outside the female.

SALMONS AND PEOPLE

Salmons are important commercial and sport fishes.

CONSERVATION STATUS

The World Conservation Union (IUCN) lists four salmons as Extinct, four as Critically Endangered, five as Endangered, and eight as Vulnerable. Extinct means no longer in existence. Critically Endangered means facing extremely high risk of extinction in the wild in the near future. Endangered means facing very high risk of extinction in the wild in the near future. Vulnerable means facing high risk of extinction in the wild. The U.S. Fish and Wildlife Services lists four species as Endangered, or in danger of extinction throughout all or a significant portion of its range, and nine as Threatened, or likely to become endangered in the near future.

CHINOOK SALMON (Oncorhynchus tshawytscha): SPECIES ACCOUNTS

Physical characteristics: Chinook salmon weigh 20 to 30 pounds (9 to 14 kilograms) and are about 4 feet (1.2 meters) long. The record weight is 136 pounds (62 kilograms), and that fish was 59 inches (1.5 meters) long. The body is streamlined and narrow from side to side. There are small black spots on the back and on the tail fin. In freshwater, chinook salmon are olive brown to red or purple. At sea, adults are dark greenish to blue-black on the back and silvery to white on the belly. There are small, dark spots along the back and upper sides and on the tail fin.

Geographic range: Chinook salmon live in the Arctic and northern Pacific oceans and inland in the land bordering those waters.

Habitat: Chinook salmon spawn in freshwater and migrate to sea for feeding and maturation. In lakes they may live in water as deep as 1,230 feet (375 meters).

Diet: In streams chinook salmon mainly eat insects and small crustaceans (krus-TAY-shuns), or water-dwelling animals that have jointed legs and a hard shell but no backbone. At sea they eat fishes, crustaceans, and other invertebrates.

Behavior and reproduction: Adult chinook salmon can migrate nearly 3,100 miles (5,000 kilometers) from the ocean upstream to spawn. In December adults start to migrate from the sea, so that they reach river mouths by early spring. The female selects the spot where she will dig her nest and aggressively drives away other females competing for the same spot. When the nest is complete, the female drops into it and is joined by the dominant male. Both fish open their mouths and vibrate, and eggs and sperm are released. The female then quickly covers the eggs by moving to the upstream edge of the nest and digging small pebbles for a new nest. This process is repeated several times until the female has released all her eggs. Spent adults usually die a few days after spawning.

Chinook salmon and people: Chinook salmon are highly regarded commercial and game fishes.

Conservation status: Chinook salmon are not threatened nor endangered. ∎

ATLANTIC SALMON (Salmo salar): SPECIES ACCOUNTS

Physical characteristics: Atlantic salmon weigh 7 to 12 pounds (3 to 5 kilograms) and are about 30 inches (76 cm) long, although the record is 4 feet, 5 inches (1.3 meters), 79 pounds (36 kilograms). The body is covered with black spots. In saltwater Atlantic salmon are blue-green overlaid with a silvery coating. They lose the silvery coat to become greenish or reddish brown mottled with red or orange in freshwater.

Geographic range: Atlantic salmon live on both sides of the northern part of the Atlantic Ocean and in rivers and lakes of the bordering land.

Habitat: Young Atlantic salmon live in freshwater. Adults live in saltwater except to spawn. These fish live in rocky runs and pools of large and small rivers as well as in lakes.

Diet: Young Atlantic salmon feed on mollusks (MAH-lusks), or animals with a soft, unsegmented body usually covered by a hard shell; crustaceans; insects; and fishes. Adults at sea feed on squid, shrimp, and fish.

Behavior and reproduction: Atlantic salmon are mostly active during the day. After living in freshwater for one to six years, Atlantic salmon migrate to the ocean, where they stay for one to four years before returning to their home river to spawn. The female selects a spawning site and digs a hole by turning on her side and flexing her body up and down, producing a current and never touching the bottom. Once the female releases her eggs, all males release their sperm, the greatest number of eggs being fertilized by the first male that enters the nest.

Atlantic salmon and people: Atlantic salmon are valued for their meat.

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

BROOK TROUT (Salvelinus fontinalis): SPECIES ACCOUNTS

Physical characteristics: Brook trout are 7 to 10 inches (18 to 25 centimeters) long and weigh less than 1 pound (0.45 kilogram), although the record is 14.5 pounds (6.6 kilograms), 31 inches (78.4 centimeters). These trout have a combination of dark green marbling on the back and dorsal fin and red spots with blue halos on the sides. While migrating, brook trout are dark green on the back, silvery on the sides, and white with pink spots on the belly.

Geographic range: Brook trout live in North America in eastern Canada, the Great Lakes region south to northern Georgia, and in isolated areas in western Canada and the western United States.

Habitat: Brook trout live in clear, cool creeks, in small to medium-sized rivers, and in lakes.

Diet: Brook trout eat worms, leeches, crustaceans, insects, mollusks, fishes, amphibians (am-FIB-ee-uns) like frogs, and even small mammals and plant matter.

Behavior and reproduction: Brook trout migrate upstream in early spring, summer, and late fall and migrate downstream in late spring and fall. A male brook trout courts females by attempting to drive them toward a suitable gravel site. If a female accepts the male, she digs the nest, then covers the eggs with small pebbles. She then moves to the upstream end of the nest and begins digging a new nest. Once the female has released all her eggs, all males release their sperm, the greatest number of eggs being fertilized by the first male that enters the nest.

Brook trout and people: Brook trout are commercially farmed. Fishermen regard these trout highly because of their fight when hooked.

Conservation status: Brook trout are not threatened or endangered. ∎

FOR MORE INFORMATION

Books:

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

Montgomery, David R. King of Fish: The Thousand-Year Run of Salmon. Boulder, CO: Westview, 2003.

Schultz, Ken. Ken Schultz's Field Guide to Freshwater Fish. New York: Wiley, 2004.

Web sites:

"Fish Facts: Atlantic Salmon." U.S. Fish and Wildlife Service. http://www.fws.gov/r5crc/fish/za_sasa.html (accessed on September 27, 2004).

"Salmon." All Science Fair Projects. http://www.all-science-fair-projects.com/science_fair_projects_encyclopedia/Salmon (accessed on September 27, 2004).

"Salmon FAQs." Northeast Fisheries Science Center. http://www.nefsc.noaa.gov/faq/fishfaq2c.html#q19 (accesssed on September 27, 2004).