How to Identify Mountain Whitefish

To identify Mountain Whitefish (Prosopium williamsoni), look at these key features.

Physical Characteristics

Body shape

torpedo

Coloration

Generally silvery to olive-brown on the back, fading to silvery sides and a white belly. Fins are typically clear to dusky. Spawning males may develop a slightly darker coloration and nuptial tubercles.

Scale type

cycloid

Mouth position

subterminal

Distinctive features

Small, subterminal mouth with no teeth on the jaws (teeth present on tongue and roof of mouth, but not prominent)., Adipose fin present (a fleshy, rayless fin between the dorsal and caudal fins), characteristic of salmonids., Large, cycloid scales., Relatively small head compared to body size., Often has a faint lateral line.

Dorsal fin

Single dorsal fin, relatively short, with 11-15 rays. Originates slightly anterior to the pelvic fins.

Tail fin

Moderately forked caudal fin.

Pectoral fin

Pectoral fins are relatively small and positioned low on the body.

Distinctive fins

Adipose fin present, characteristic of salmonids.

Identification Tips

1. 1

   Mouth

   Look for a small, subterminal mouth (underslung) with no prominent teeth on the jaws. This distinguishes it from trout and char which have larger, terminal mouths with well-developed teeth.

2. 2

   Adipose Fin

   The presence of an adipose fin confirms it is a salmonid. Its overall body shape and mouth differentiate it from trout and salmon.

3. 3

   Scales

   Mountain Whitefish have relatively large, smooth (cycloid) scales, which are more prominent than the smaller scales found on many trout species.

4. 4

   Body Shape

   Its slender, cylindrical body is distinct from the more robust, often deeper-bodied trout and char.

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