How to Identify Cutthroat Trout

To identify Cutthroat Trout (Oncorhynchus lewisi), look at these key features.

Physical Characteristics

Body shape

torpedo

Coloration

Highly variable depending on subspecies, habitat, and age. Generally, olive-green to yellowish-brown on the back, fading to silvery or white on the belly. Sides often have red or pinkish hues, especially during spawning. Distinctive black spots are typically concentrated towards the tail, but can extend over the entire body. The most defining feature is the red, orange, or pinkish-red 'slash' marks on the underside of the lower jaw.

Scale type

cycloid

Mouth position

terminal

Distinctive features

Red, orange, or pinkish-red 'slash' marks on the underside of the lower jaw., Presence of basibranchial (hyoid) teeth, a key diagnostic feature for the genus Oncorhynchus., Small, numerous black spots, often concentrated posteriorly., Typically a longer, more slender body shape compared to some other trout species.

Dorsal fin

Single, relatively short dorsal fin with 10-12 rays.

Tail fin

Slightly forked to truncate caudal fin.

Pectoral fin

Moderately sized pectoral fins.

Distinctive fins

Adipose fin present, characteristic of salmonids.

Identification Tips

1. 1

   Jaw Slashes

   Look for the characteristic red, orange, or pinkish-red marks on the underside of the lower jaw. These can sometimes be faint or absent in very young fish or certain populations, but are generally present.

2. 2

   Spotting Pattern

   Cutthroat Trout typically have numerous small, irregular black spots, often more concentrated towards the tail and on the dorsal fin. The spots are generally smaller and more numerous than those on Rainbow Trout.

3. 3

   Basibranchial Teeth

   A definitive identification feature for Oncorhynchus species, including Cutthroat Trout, is the presence of a small patch of teeth on the base of the tongue (basibranchial or hyoid teeth). This requires careful examination.

4. 4

   Maxillary Extension

   The maxillary (upper jaw bone) typically extends beyond the posterior margin of the eye in adult Cutthroat Trout.

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