How to Identify Eulachon

To identify Eulachon (Thaleichthys pacificus), look at these key features.

Physical Characteristics

Body shape

elongated

Coloration

Dorsal surface is typically iridescent blue-black to brownish-green, fading to silvery on the sides and belly. The operculum (gill cover) often has a metallic sheen.

Scale type

cycloid

Mouth position

terminal

Distinctive features

Adipose fin present (a small, fleshy fin without rays, located between the dorsal and caudal fins), characteristic of smelts and salmonids., Large mouth extending to the middle of the eye., Prominent concentric striations on the operculum., Small, sharp teeth on the tongue and jaws., High oil content, making them feel greasy to the touch.

Dorsal fin

Single dorsal fin, typically with 10-13 soft rays, located mid-body.

Tail fin

Deeply forked caudal fin.

Pectoral fin

Pectoral fins are relatively large and low-set.

Distinctive fins

Presence of an adipose fin.

Identification Tips

1. 1

   Size

   Adults typically range from 15-23 cm (6-9 inches) in length, rarely exceeding 30 cm (12 inches).

2. 2

   Coloration

   Iridescent blue-black to brownish-green dorsally, silvery flanks and belly.

3. 3

   Adipose Fin

   Presence of a small, fleshy adipose fin between the dorsal and caudal fins is a key characteristic of the family Osmeridae.

4. 4

   Mouth

   Large mouth, extending to the middle of the eye, with small, sharp teeth.

5. 5

   Operculum

   Distinctive concentric striations (ridges) on the operculum (gill cover).

6. 6

   Texture

   Very oily and slippery to the touch due to high fat content.

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