How to Identify Cutthroat Trout

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

Physical Characteristics

Body shape

torpedo

Coloration

Highly variable depending on subspecies, habitat, and age. General coloration ranges from silver to brassy green, olive, or yellowish-brown on the sides, often with darker backs and lighter bellies. Distinctive black spots are typically present on the body, fins, and head, often concentrated towards the tail. The most defining feature is the red, orange, or pinkish-red slash mark on the underside of the lower jaw, though its intensity varies.

Scale type

cycloid

Mouth position

terminal

Distinctive features

Red/orange/pinkish-red slash mark on the underside of the lower jaw (often faint or absent in some populations)., Presence of basibranchial (hyoid) teeth, a key diagnostic feature distinguishing them from Rainbow Trout., Numerous small, irregular black spots, often concentrated towards the caudal fin., Maxillary bone extends beyond the posterior margin of the eye in adults.

Dorsal fin

Single dorsal fin, typically with 8-11 rays.

Tail fin

Slightly forked to emarginate (nearly straight) caudal fin.

Pectoral fin

Paired pectoral fins, typically with 12-16 rays.

Distinctive fins

Adipose fin present, characteristic of salmonids. Pelvic fins are abdominal.

Identification Tips

1. 1

   Red/Orange Jaw Slash

   Look for the characteristic red, orange, or pinkish-red mark in the fold of the lower jaw. While sometimes faint or absent, its presence is a strong indicator.

2. 2

   Basibranchial Teeth

   A definitive internal diagnostic feature: Cutthroat Trout possess a small patch of teeth on the basibranchial bone (at the base of the tongue), which Rainbow Trout lack. This requires careful examination.

3. 3

   Spotting Pattern

   Cutthroat Trout typically have numerous, small, irregular black spots, often more concentrated towards the tail and on the fins. Rainbow Trout often have more evenly distributed, larger spots.

4. 4

   Maxillary Length

   In adults, the maxillary bone (upper jaw bone) typically extends beyond the posterior margin of the eye, a feature often less pronounced in Rainbow Trout.

5. 5

   Absence of White Fin Tips

   Unlike Brook Trout (Salvelinus fontinalis), Cutthroat Trout do not have white leading edges on their pectoral, pelvic, and anal fins.

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