Lake 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.
  • Close-up anal fin: Notice the absence of a black stripe in the fin.
  • Top view: Notice the light colored mottling ("vermiculations") on a darker green background.
  • View of intestine: There are 93-208 pyloric caecae.
  • Close-up tail: The tail is strongly forked.
  • Close-up flank: Notice the light spots on dark background, but no red spots.
  • Close-up underside of head: There are 9-10 mandibular pores on each side of the jaw.
  • Close-up flank of a young-of-year: Notice the parr marks.
  • Close-up tail region of a young-of-year: Notice the parr marks.
  • Side view of a young-of-year: Notice the parr marks.
  • Close-up head region of a young-of-year: Notice the parr marks.
  • Alternative side view.
  • Side view of the siscowet form, held by Mike Hoff, U.S. Geological Survey -BRD.
  • Close-up head of the siscowet form.
  • Side views of siscowet form (top), "half breed" form (middle), and "lean" form (bottom).
  • Alternative side view.
  • Alternative view of the head.
  • Side view of a brook trout X lake trout hybrid: Notice the intermediate appearance.
  • Close-up flank of a brook trout X lake trout hybrid: Notice the intermediate appearance and the faint red spots without blue "halos".
  • Close-up tail of a brook trout X lake trout hybrid: Notice the intermediate appearance and the moderately forked tail with pointed caudal lobes.
  • Intestine of a brook trout X lake trout hybrid: Notice the intermediate appearance; there are 65-85 pyloric caecae.
  • Side view of a brook trout X lake trout hybrid: Notice the intermediate appearance.
  • Side view of a brook trout X lake trout young-of-year hybrid: Notice the intermediate appearance and the parr marks.
  • Close-up anal fin of a brook trout X lake trout hybrid: Notice the intermediate appearance and the weakly developed black stripe after a white leading edge.
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, mottling or irregular blotches on back (“vermiculations”); juveniles with thick dark vertical bars (“parr marks”). Background body color dark olive, dark green, or dark gray on back and sides grading to cream on belly. Vermiculations lighter olive or gray; spots cream to light olive. 163-210 cycloid lateral line scales. Dorsal and tail fins with lighter spots and vermiculations on a darker olive or gray background; pectoral, pelvic, and anal fins more or less uniformly colored olive, gray, or light orange, sometimes with a whitish edge or faint spots. Body shape and size: Body fusiform; oval in cross section. The “siscowet” or “fat” form from offshore waters of Lake Superior has a blunter head and may have a deeper body than the “lean” form from nearshore areas of Lake Superior, Lake Michigan, and inland lakes. Typically 500-750 mm (20-30 in) TL; maximum over 1000 mm (40 in).
Fins
Tail, dorsal and other fins: Forked 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 11.
Distinguishing Characteristics
The lake trout can be distinguished by its strongly forked tail, lack of red spots on body, pectoral, pelvic and anal fins more or less uniformly colored, sometimes with faint spots or a narrow white border, 12-24 gill rakers, and 9-10 mandibular pores on each side of the jaw. See also similar species information.
Breeding Adults
Males may occasionally have a prominent dark lateral stripe.
Juveniles
Have 7-12 broad oval vertical bars (“parr marks”) on sides. Vermiculations are more pronounced and spots less conspicuous than in adults, giving the fish a more mottled appearance, especially on the back.
Hybrids
Brook trout X lake trout (“Splake”), artificially produced in hatcheries and stocked in a few areas of the Great Lakes.
Compare Similar Species
Tail Shape
Trout, BrookWeakly forked
Trout, LakeStrongly forked
Body Pattern
Trout, BrookRed spots
Trout, LakeNo red spots
Pectoral, Pelvic, and Anal Fin Pigmentation
Trout, BrookThin white stripe on the edge followed by a black stripe oftentimes with redish coloration
Trout, LakeNo stripes
Gill Rakers
Trout, Brook9-12
Trout, Lake12-24
Mandibular Pores
Trout, Brook7-8
Trout, Lake9-10
Similarity Index
Trout, BrookVery similar
Trout, LakeN/A
Comments
Trout, LakeModerately similar to other trout and salmon, but distinguishable by its pattern of light spots on a dark background
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