Sea-run Atlantic salmon usually attain a larger size than do landlocked (those living in entirely fresh water) salmon. Sea-run salmon range from 2.3 to 9.1 kg and commercially caught fish average 4.5 to 5.4 kg. The world record rod-caught Atlantic salmon weighed 35.89 kg and was caught in the Tana River of Norway.
The adult Atlantic salmon is a graceful fish, deepening rearward from a small pointed head to the deepest point under the dorsal fin, then tapering to a slender caudal peduncle which supports a spreading and slightly emarginate caudal fin. Atlantic salmon are distinguished from the Pacific salmon because they have fewer than 13 rays in the anal fin. Their mouth is moderately large. The shape, length of head, and depth of body vary with each stage of sexual maturity.
Color varies with age of this fish. Small "parr," older young salmon, have 8 to 11 pigmented bars, or "parr marks," along each side of their body, alternating with a single row of red spots along the lateral line. These markings are lost when the "smolt" age is reached. Salmon in the sea are silvery on the sides and belly, while the back varies with shades of brown, green, and blue. Atlantic salmon also have numerous black spots, usually "X"-shaped and scattered around the body. When spawning, both sexes take on an overall bronze-purple coloration and may acquire reddish spots on the head and body. After spawning, the "kelts" are so dark in color that these fish are also called "black salmon"
(Eddy and Underhill, 1974; Bigelow, 1963; Scott and Crossman, 1973).
Range mass: 2.3 to 35.89 kg.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry