How to Identify Steelhead Trout

To identify Steelhead Trout (Oncorhynchus mykiss irideus), look at these key features.

Physical Characteristics

Body shape

torpedo

Coloration

In freshwater, they typically exhibit a silvery-blue to olive-green back, silvery sides, and a white belly, often with a prominent pink or reddish stripe along the lateral line. Numerous small, dark spots are present on the back, dorsal fin, and caudal fin. In marine environments, they are predominantly bright silver with a darker dorsal surface, often lacking the prominent pink stripe, which develops upon return to freshwater for spawning.

Scale type

cycloid

Mouth position

terminal

Distinctive features

Anadromous life history (sea-run form of Rainbow Trout), Silvery coloration in marine phase, developing a pink stripe in freshwater spawning phase, Numerous small, dark spots on back, dorsal fin, and caudal fin, Adipose fin present

Dorsal fin

Single dorsal fin, typically with 10-12 rays, located mid-body.

Tail fin

Moderately forked caudal fin, often with dark spots.

Pectoral fin

Paired pectoral fins, relatively small.

Distinctive fins

Presence of a small, fleshy adipose fin between the dorsal and caudal fins, characteristic of salmonids.

Identification Tips

1. 1

   Coloration

   Look for the silvery sheen in ocean-phase fish, and the developing pink lateral stripe and darker back in freshwater-returning fish. The presence of numerous small, dark spots on the back and tail is key.

2. 2

   Adipose Fin

   The small, fleshy adipose fin between the dorsal and caudal fins confirms it is a salmonid.

3. 3

   Size

   Steelhead are generally much larger than resident Rainbow Trout due to their ocean feeding phase.

4. 4

   Fin Spots

   Distinctive spotting pattern on the dorsal and caudal fins helps differentiate from some other salmonids.

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