Atlantic salmon in the ocean tend to be silvery with white undersides. However,
freshwater Atlantic salmon tend to be much darker and lack the silvery color. Upon sexual
maturity and as spawning time nears, the fish become bronze and/or dark brown, and they
may have some reddish spots on the head and body. It can be difficult to distinguish the
spawning Atlantic salmon from the brown trout. The spawning males develop an elongated
head and a large, hooked lower jaw. After spawning, males and females both take on even
darker colors. 
Look for:
- Few (2 or 3) large spots on gill cover
- No red/orange on adipose fin (brown trouts do have this red/orange)
- No radiating rows of black spots on tail fin, which is usually entirely without spots
- Reddish brown spots on sides of body except in large lake-run individuals
- More than 19 whitish gill rakers on inside of first gill arch (the red gill filaments
are on the outside of the arch)
- Fewer than 120 scales in lateral line (brown trouts have more)
- Spots on head and body dark and light background
- Pelvic and anal fins usually without white leading (front) edges
- Nine rays in anal fin
Complete atlantic salmon
profile.
Main trouts and salmons page.
Sources: "Fishes of Isle Royale," by K.F. Lagler and C. R.
Goldman, Isle Royale Natural History Association, 1982.
Fishes of Wisconsin, by George C. Becker, University of Wisconsin
Press, 1983.
Freshwater Fishes of Canada, by W.B. Scott and E.J. Crossman, Fisheries Research
Board of Canada, 1973.
