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Petrale Sole - Photo by S. Axtell

Bottomfish Identification: Flatfish

This flatfish identification guide is intended to provide information and key characteristics for the most common flatfish species in Washington marine waters.  To access species information click on the common or scientific name listed in the left hand column.  For each species, information is available on expected sizes, typical distribution, and published ages. 



Some key identification characteristics to look for are:

Anal spine

This is a hard, sharp spine pointing forward and located in front of the anal fin, near the anus.

Accessory dorsal branch (ADB)

A branch of the lateral line running from near the head back toward the tail, just below the base of the dorsal fin.

Lateral line

A series of modified scales with pore-like openings to a sensory canal along the side of a fish.

Eyed side

The top side of a flatfish.  This side has eyes and is more darkly pigmented than the side that lies against the bottom (blind side).       

For additional identification assistance, a dichotomous key for flatfish is available through the Oregon Department of Fish and Wildlife’s Webpage at:

The NOAA-Alaska Fisheries Science Center also provides identification information about flatfish common off the Alaskan Coast at:

Enjoy learning about Washington’s flatfish!

Arrowtooth Flounder (Atheresthes stomias) Pacific Sanddab (Citharichthys sordidus)
Butter Sole (Pleuronectes isolepis) Petrale Sole (Eopsetta jordani)
Curlfin Sole (Pleuronichthys decurrens) Rex Sole (Errex zachirus)
Dover Sole (Microstomus pacificus) Rock Sole (Pleuronectes bilineatus)
English Sole (Pleuronectes vetulus) (formerly (Parophrys vetulus)) Sand Sole (Psettichthys melanostictus)
Flathead Sole (Hippoglossoides elassodon) Speckled Sanddab (Citharichthys stigmaeus)
Pacific Halibut (Hippoglossus stenolepis) Starry Flounder (Platichthys stellatus)