Coho Salmon
  • Side view of two adults.
  • Side view adult.
  • Side view adult.
  • Top view adult.
  • Bottom view adult.
  • Head-on view adult.
  • Close-up flank.
  • Close-up head.
  • Close-up mouth and snout.
  • Close-up tail.
  • Close-up dorsal fin.
  • Close-up anal fin.
  • Close-up pectoral fin.
  • Close-up pelvic fin.
  • The head region shows dark spots on light background. The spots are much smaller than the pupil.
  • Close-up of underside of head: There are usually 11-15 branchiostegal rays on each side. The jaw of this specimen has a hook wound.
  • The inside of the mouth of this breeder is blackish, but gums around the teeth are white.
  • The flanks show small dark spots on light background, no red spots, and 112-148 lateral line scales.
  • The tail lacks spots; some can be seen on top of the upper lobe in spawners.
  • There are 9-12 principal dorsal rays, the dorsal fin shows few or no spots.
  • Close-up of tail region of a young-of-year: The adipose fin is not edged in red; the anal fin is highly falcate.
  • There are 12-17 principal anal rays; the anal fin shows few or no spots.
  • The image shows a juvenile fish. There are 45-114 pyloric caecae.
  • This female specimen developed a dark blue to silver color.
  • This female specimen developed a dark blue-black color.
  • Close-up anal fin: There are 12-17 principal anal rays and few spots on a dark color background.
  • Close-up tail of male and female breeders: The tail is only spotted on top of the upper lobe and shows a concave shape (no fork).
  • Close-up heads of male (bottom) and female (top) breeders: Notice the hooked jaw in the male.
  • Side view of two breeders: Female (top) and male (bottom).
  • Side view of a female breeder: This female specimen developed a dark blue-black color.
  • Side view of a breeding male: This male specimen developed a reddish-purple color.
  • Close-up flank of a breeding male: Notice the reddish-purple color.
  • Close-up tail region of a young-of-year: They have 12-17 principal anal rays with the 1st rays being elongated; the fin is strongly falcate.
  • Young-of-year develop parr marks.
  • Young-of-year develop parr marks.
  • The parr marks of this yearling are almost gone, the fish is beginning to smolt.
DescriptionSimilar Species
Family
Trouts (Salmonidae)
Body
Mouth and snout: Terminal, large and slightly oblique, with numerous small to medium-sized teeth on the upper and lower jaws. No barbels. Body patterning, color, and scales: SPOTS on back and upper sides, but few and faint in some individuals, giving the appearance of a solid color; juveniles also with oval dark vertical bars (“parr marks”). Background body color silvery, silver-blue, or light olive, grading to cream on belly. Spots dark brown or black; round or irregular in shape, substantially smaller than the pupil of the eye. 112-148 cycloid lateral line scales. Dorsal and tail fins tan, olive, or gray; usually with few spots. In dorsal spots limited to base of fin; in tail spots limited to top of upper lobe. Pectoral, pelvic, and anal fins dark gray; not spotted. Adipose fin not edged in red or orange. Body shape and size: Body fusiform; oval in cross section. In Great Lakes, typically 400-650 mm (16-26 in) TL; maximum about 750 mm (30 in).
Fins
Tail, dorsal and other fins: Slightly forked to squared tail. Single dorsal fin with no spines and 10-15 principal rays. Pelvic fins abdominal with axillary process. Adipose fin present. Anal fin with 12-17 principal rays.
Distinguishing Characteristics
The coho salmon can be most easily distinguished by its pattern of dark spots on a light background, as opposed to light spot and blotches on a dark background. See also similar species information.
Breeding Adults
Males develop a hooked jaw. The body and fins of both sexes become darker (bronze, brown, or dark gray) with more pronounced spots prior to spawning and turn black after spawning. Males may have reddish or reddish-purple sides during spawning, with head and fins dark gray.
Juveniles
Have 8-12 oval vertical bars (“parr marks”) on sides. Spots relatively scarce and inconspicuous in young-of-year fish. First principal rays of anal fin substantially longer than subsequent rays, making fin distinctly falcate. Older juveniles have more adult-like spotting patterns but retain parr marks, which disappear as the fish smolt and leave the natal stream and move into the Great Lakes.
Hybrids
None known from Wisconsin.
Compare Similar Species
Spot Characteristics
Salmon, AtlanticUsually few, covering upper sides; black & sometimes red present; nearly as large as pupil of eye; round, irregular ovals, or “X” shaped
Salmon, ChinookModerate to numerous, limited to upper half of sides; black only; much smaller than pupil of eye; round or irregular in shape
Salmon, CohoUsually few, and limited to back and upper sides; black only; much smaller than pupil of eye; round or irregular in shape
Salmon, KokaneeAlmost none, limited to upper back; black only; much smaller than pupil of eye; round to slightly oval in shape
Salmon, PinkNumerous and on both lobes, forming lines of elongated oval spots along rays
Trout, BrookModerate to numerous; covering sides; cream, light, olive, yellow, red, sometimes with bluish halo; much smaller than pupil of eye; round
Trout, BrownFew to many, covering most of sides; both black and red present; nearly as large as pupil of eye; round or irregular ovals in shape
Trout, LakeMany; covering sides; cream to light olive; much smaller than pupil of eye; irregular shape, much smaller than pupil of eye
Trout, RainbowMany, covering most of sides; black only; much smaller than pupil of eye; round or irregular in shape
Tail Spots
Salmon, AtlanticFew or none, usually limited to base of tail
Salmon, ChinookModerate to numerous and on both lobes
Salmon, CohoFew, limited to top of upper lobe
Salmon, KokaneeNone
Salmon, PinkNumerous and on both lobes, forming lines of elongated oval spots along rays
Trout, BrookFew and lighter
Trout, BrownFew or none, usually limited to base of tail
Trout, LakeNumerous and on both lobes
Trout, RainbowNumerous and on both lobes
Principal Anal Rays
Salmon, Atlantic7-12, usually 9-11
Salmon, Chinook14-19
Salmon, Coho12-17, 1st ray elongated; fin distinctly falcate in YOY
Salmon, Kokanee11-16, usually 13-14
Salmon, Pink13-19
Trout, Brook7-13, usually 9
Trout, Brown8-12, usually 9-11
Trout, Lake8-10
Trout, Rainbow8-12
Lateral Line Scales
Salmon, Atlantic109-121
Salmon, Chinook130-165
Salmon, Coho112-148
Salmon, Kokanee121-140
Salmon, Pink147-205
Trout, Brook210-244
Trout, Brown120-130
Trout, Lake185-210
Trout, Rainbow100-150
Inside of Mouth in Breeders
Salmon, AtlanticWhite
Salmon, ChinookBlack or dark gray
Salmon, CohoBlack or gray; gums white
Salmon, KokaneeDark gray with white mottling
Salmon, PinkTongue and tip of jaw black or gray; gums white
Trout, BrookWhite on the teeth, tongue, and inside of mouth, but black on the gums
Trout, BrownWhite
Trout, LakeWhite
Trout, RainbowWhite
Other Features
Salmon, AtlanticBranchiostegal rays usually 11-12, principal dorsal rays 11-12, adipose fin not edged in red, pyloric caecae 40-74, gill rakers 15-20, vomerine teeth poorly developed, dorsal fin with few or no spots
Salmon, ChinookBranchiostegal rays usually 13-19, principal dorsal rays 10-14, adipose fin not edged in red, pyloric caecae 140-185, gill rakers 16-26, vomerine teeth well developed, dorsal fin spotted
Salmon, CohoBranchiostegal rays usually 11-15, principal dorsal rays 9-12, adipose fin not edged in red, pyloric caecae 45-114, gill rakers 18-25, vomerine teeth well developed, dorsal fin with few or no spots
Salmon, KokaneeBranchiostegal rays usually 13-14, principal dorsal rays 11-13, adipose fin not edged in red, pyloric caecae 50-87, gill rakers 29-43, vomerine teeth well developed, dorsal fin with few or no spots
Salmon, PinkBranchiostegal rays usually 9-15, principal dorsal rays 10-15, adipose fin not edged in red, pyloric caecae 95-224, gill rakers 24-35, vomerine teeth well developed, dorsal fin with few or no spots
Trout, BrookBranchiostegal rays usually 9-13, principal dorsal rays 10-14; adipose fin not edged in red, but dark margin in young; pyloric caecae 23-55; gill rakers 9-12; vomerine teeth well developed; dorsal fin spotted
Trout, BrownBranchiostegal rays usually 10, principal dorsal rays 9-11, adipose fin often edged in red, pyloric caecae 30-60, gill rakers 14-17, vomerine teeth well developed, dorsal fin spotted
Trout, LakeBranchiostegal rays usually 10-14, principal dorsal rays 8-10, adipose fin not edged in red, pyloric caecae 93-208, gill rakers 16-26, vomerine teeth well developed, dorsal fin spotted
Trout, RainbowBranchiostegal rays usually 9-13, principal dorsal rays 10-12, adipose fin not edged in red, pyloric caecae 27-80, gill rakers 16-22, vomerine teeth well developed, dorsal fin heavily spotted
Similarity Index
Salmon, AtlanticVery similar
Salmon, ChinookVery similar
Salmon, CohoN/A
Salmon, KokaneeVery similar
Salmon, PinkVery similar
Trout, BrookModerately similar
Trout, BrownVery similar
Trout, LakeModerately similar
Trout, RainbowVery similar
Comments
Salmon, AtlanticNot native; stocked in the past without estabishing a population. Occurs only in the Great Lakes as a rare stray from other states and Ontario.
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