Brown Trout
  • Side view adult.
  • 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.
  • There are 30-60 pyloric caecae.
  • Close-up of tail region: The adipose fin is edged in red.
  • Close-up of lower jaw: There are usually 10 branchiostegal rays on each side.
  • The inside of the mouth of this breeder is white.
  • The inside of the mouth displays well-developed vomerine teeth.
  • The tail lacks spots.
  • The flank displays dark spots on a light background and red spots; there are 120-130 lateral line scales.
  • Close-up of the head: Notice the dark spots on a light background and the red spots; some of the black spots are nearly as large as the pupil.
  • Close-up of anal fin: There are 8-12, usually 9-11, principal anal rays.
  • Close-up of the dorsal fin: There are 9-11 prinipal dorsal rays; the dorsal fin is spotted.
  • Side view of a breeder: Notice the hooked lower jaw and the hump on the back.
  • Close-up head: Notice the hooked lower jaw and the hump on the back.
  • Side view of a breeder: Male breeders develop hooked lower jaws.
  • Side view of a breeder: Notice the numerous, large, dark spots.
  • Close-up of the head of a breeder: Notice the slight hook of the lower jaw.
  • Close-up of flank: Notice the absence of red spots.
  • Side view of two young-of-year: Notice the parr marks and the few spots; the adipose fin is yellowish-orange.
  • Side view of a young-of-year: Notice the parr marks and the red adipose fin.
  • Side view of a young-of-year: Notice the parr marks and the red adipose fin.
  • Side view of a juvenile: Notice the parr marks beginning to fade.
  • View of underside of the lower jaw: Both sides display 10 branchiostegal rays.
  • Brook trout X brown trout hybrid: Notice the intermediate appearance.
  • Close-up anal fin of a brook trout X brown trout hybrid: Notice the intermediate appearance as well as the white leading edge without a black stripe.
  • Close-up flank of a brook trout X brown trout hybrid: Notice the intermediate appearance as well as the irregular mottling on bronze/reddish background.
  • Top view of a brook trout X brown trout hybrid: Notice the intermediate appearance as well as the weakly developed "vermiculations".
  • Brook trout X brown trout hybrid: Notice the intermediate appearance.
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 side; juveniles also with thick dark vertical bars (“parr marks”). Background body color tan, brown, or olive brown (inland populations) or silvery (Great Lakes) grading to cream on belly. Spots dark brown, black, and red (red may be faded or absent in Great Lakes), some round and others irregular ovals in shape, some nearly as large as the pupil of the eye. 120-130 cycloid lateral line scales. Dorsal and tail fins brown; dorsal heavily spotted, tail with few or no spots. Pectoral, pelvic, and anal fins light brown, tan, or yellowish without spots; anal fin may have a white leading edge. Adipose fin usually edged in red or orange (often faded or absent in Great Lakes). Body shape and size: Body fusiform; oval in cross section. Inland typically 250-400 mm (10-16 in) TL; maximum about 600 mm (24 in). Great Lakes typically 450-650 (18-26 in); maximum about 800 mm (32 in).
Fins
Tail, dorsal and other fins: Slightly forked to square tail. Single dorsal NO SPINES and 12-14 principal rays. Pelvic fins abdominal with axillary process. Adipose fin present. Anal fin with 7-12 principal rays, usually 9-11.
Distinguishing Characteristics
The brown trout can be distinguished by its pattern of dark spots on a light background. See also similar species information.
Breeding Adults
Males develop a hooked lower jaw.
Juveniles
Have 7-12 broad oval vertical bars (“parr marks”) on sides. Spots relatively scarce and inconspicuous in young-of-year fish. Older juveniles have more adult-like spotting patterns but retain parr marks, which gradually fade with age.
Hybrids
Brook trout X brown trout (“Tiger trout”), rare natural hybrid in Wisconsin; produced in hatcheries and stocked in 1970s.
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 to upper back; black only;
Salmon, PinkModerate in number, covering upper sides; black only; nearly as large as pupil of eye; round or oval in shape
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
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 & 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 & on both lobes
Principal Anal Rays
Salmon, Atlantic7-12 usually 9-11
Salmon, Chinook14-19
Salmon, Coho12-17 First 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 & 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 Principal dorsa
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, ChinookModerately similar
Salmon, CohoModerately similar
Salmon, KokaneeModerately similar
Salmon, PinkModerately similar
Trout, BrookModerately similar
Trout, BrownN/A
Trout, LakeModerately similar
Trout, RainbowModerately 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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