How to Identify Blue Rockfish

To identify Blue Rockfish (Sebastes mystinus), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Typically dark blue to blue-gray on the dorsal side, fading to a lighter blue or white on the ventral side. Often exhibits faint, irregular dark blotches or mottling on the sides. Fins are usually dark. Juveniles may have more pronounced mottling or a reddish tint.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

Relatively small mouth with a slightly projecting lower jaw., Large eyes., Absence of strong spines on the head (unlike many other rockfish species)., Smooth, rounded profile of the head., Often forms large schools in the water column.

Dorsal fin

Single, long dorsal fin with 13 spines and 13-16 soft rays. The spiny and soft-rayed portions are deeply notched.

Tail fin

Caudal fin is moderately forked.

Pectoral fin

Pectoral fins are relatively long and rounded.

Distinctive fins

Anal fin has 3 spines and 8-10 soft rays. Pelvic fins are thoracic with 1 spine and 5 soft rays.

Identification Tips

1. 1

   Coloration

   Look for the characteristic dark blue to blue-gray body, often with faint, irregular darker blotches. The overall impression is a uniformly blue fish.

2. 2

   Head Spines

   Unlike many other rockfish, the Blue Rockfish has a relatively smooth head with no prominent spines on the operculum or preoperculum, which helps distinguish it from species like the Black Rockfish.

3. 3

   Mouth and Jaw

   Observe the relatively small mouth and the slightly projecting lower jaw. The mouth does not extend past the posterior margin of the eye.

4. 4

   Dorsal Fin Notch

   Note the deep notch between the spiny and soft-rayed portions of the dorsal fin.

5. 5

   Schooling Behavior

   Blue Rockfish are often found in large, dense schools in the midwater column, a behavior less common in some other solitary rockfish species.

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