How to Identify Rainbow Smelt

To identify Rainbow Smelt (Osmerus mordax), look at these key features.

Physical Characteristics

Body shape

elongated

Coloration

Dorsal surface is typically olive-green to pale brown, fading to silvery sides and a white belly. A distinct iridescent purplish-pink lateral band is often visible, especially in fresh specimens. Fins are generally clear to dusky.

Scale type

cycloid

Mouth position

terminal

Distinctive features

Slender, elongated body, Large mouth extending to the posterior margin of the eye, Prominent canine-like teeth on the tongue and jaws, Adipose fin present (small, fleshy fin between dorsal and caudal fins), Strong cucumber-like odor when freshly caught

Dorsal fin

Single, relatively short dorsal fin located mid-body, typically with 8-11 soft rays.

Tail fin

Deeply forked caudal fin.

Pectoral fin

Pectoral fins are relatively long and low-set.

Distinctive fins

Presence of a small, fleshy adipose fin posterior to the dorsal fin, characteristic of the family Osmeridae.

Identification Tips

1. 1

   Body Shape and Coloration

   Look for a slender, silvery body with an olive-green to brownish back and a distinct iridescent lateral band. The overall appearance is sleek and streamlined.

2. 2

   Mouth and Teeth

   Open the mouth and check for prominent, sharp, canine-like teeth on the tongue and jaws. The mouth is relatively large, extending to or beyond the middle of the eye.

3. 3

   Adipose Fin

   Confirm the presence of a small, fleshy adipose fin between the dorsal fin and the caudal fin. This is a key characteristic of smelts.

4. 4

   Odor

   When freshly caught, Rainbow Smelt emit a distinctive odor often described as similar to fresh cucumber. This is a reliable field identification cue.

5. 5

   Size

   Adults typically range from 15-25 cm (6-10 inches) in length, though some individuals can reach up to 35 cm (14 inches).

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