How to Identify Coastal Cutthroat Trout

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

Physical Characteristics

Body shape

torpedo

Coloration

Highly variable depending on habitat and life history. Freshwater residents are typically olive-green to brassy-yellow on the back, fading to silvery sides and a white belly. Sea-run individuals are bright silver with a dark back, often with a bluish sheen. All forms have numerous small, irregular black spots concentrated towards the tail. The most distinctive feature is the red to orange 'cutthroat' slash on the underside of the lower jaw, though this can be faint or absent in some individuals, especially sea-run fish.

Scale type

cycloid

Mouth position

terminal

Distinctive features

Red or orange 'cutthroat' slashes on the underside of the lower jaw (can be faint or absent)., Numerous small, irregular black spots, often concentrated on the posterior half of the body and fins., Maxillary bone extends well beyond the posterior margin of the eye in adults., Presence of basibranchial (hyoid) teeth, which can be felt by running a finger along the floor of the mouth.

Dorsal fin

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

Tail fin

Slightly forked to truncate caudal fin.

Pectoral fin

Paired pectoral fins, moderately sized.

Distinctive fins

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

Identification Tips

1. 1

   Cutthroat Slashes

   Look for the distinctive red, orange, or yellow-orange markings on the underside of the lower jaw. These can vary in intensity and may be faint or absent in some individuals, especially sea-run fish.

2. 2

   Spotting Pattern

   Coastal Cutthroat Trout typically have numerous small, irregular black spots, often more concentrated towards the tail and on the dorsal and caudal fins. This differs from Rainbow Trout (Oncorhynchus mykiss) which tend to have more evenly distributed spots.

3. 3

   Maxillary Length

   In adults, the maxillary bone (upper jaw bone) extends noticeably beyond the posterior margin of the eye. This is a key differentiator from Rainbow Trout, where the maxillary typically does not extend as far.

4. 4

   Basibranchial Teeth

   A definitive identification feature is the presence of basibranchial (hyoid) teeth on the floor of the mouth. These can be felt by gently running a finger along the tongue area. This feature is absent in Rainbow Trout.

5. 5

   Coloration

   While variable, freshwater forms often have a more olive to brassy hue, while sea-run forms are distinctly silvery with a darker back.

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