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Rex Sole

Glyptocephalus zachirus

Rex Sole image

Also Known As

  • Witch sole
  • Threadfin sole

U.S. wild-caught rex sole is a smart seafood choice because it is sustainably managed and responsibly harvested under U.S. regulations.

Population

Above target population levels in the Gulf of Alaska and on the West Coast. The population level is unknown in the Bering Sea/Aleutian Islands.

Fishing Rate

At recommended levels.

Habitat Impacts

Area closures and gear restrictions protect habitats that are affected by bottom trawls used to harvest rex sole.

Bycatch

Regulations are in place to minimize bycatch.

  • Availability

    Year-round, but highest catch is from February through May. 

  • Source

    U.S. wild-caught from Alaska to California (but mainly from Alaska).

  • Taste

    Mild and sweet.

  • Texture

    Tender with fine, firm flakes.

  • Color

    White when raw or cooked.

  • Health Benefits

    Rex sole is an excellent source of low-fat protein.

The U.S. Fishery

Fishery Management

  • NOAA Fisheries and the Pacific Fishery Management Council manage the rex sole fishery on the West Coast.
  • Managed under the Pacific Coast Groundfish Fishery Management Plan:
    • Limits on the number of permits and fishermen allowed.
    • Limits on the minimum size of fish that may be harvested.
    • Limit on how much may be harvested in one fishing trip.
    • Certain seasons and areas are closed to fishing.
    • Observers are required and gear restrictions help reduce bycatch and impacts on habitat.
    • A trawl rationalization catch share program includes:
      • Catch limits based on the population information for each fish stock and divided into shares that are allocated to individual fishermen or groups.
      • These fishermen can decide how and when to catch their share – preferably when weather, markets, and business conditions are most favorable, allowing the fishery the flexibility to be more environmentally responsible, safer, more efficient, and more valuable.
  • In the Gulf of Alaska, Bering Sea, and Aleutian Islands:
    • Fishermen must have a permit to participate in these fisheries, and the number of available permits is limited to control the amount of fishing.
    • Managers determine how much rex sole can be caught. Catch is monitored through record keeping, reporting requirements, and observer monitoring.

Harvest

  • In 2016, landings of rex sole totaled more than 6.9 million pounds and were valued at more than $2.5 million.
  • Gear types, habitat impacts, and bycatch:
    • Bottom trawls are used to catch rex sole.
    • Trawls that are used to harvest rex sole can contact the ocean floor and impact habitats, depending on the characteristics of the ocean bottom and the size of the gear.
    • Bottom trawls cause minimal damage to habitat when targeting rex sole over soft, sandy, or muddy ocean bottoms on the West Coast and in Alaska.
    • In Alaska and on the West Coast, NOAA Fisheries and the regional fishery management councils have implemented large closed areas to protect sensitive rocky, cold-water coral and sponge habitats from bottom trawls.
    • Vessel monitoring systems allow enforcement staff and fishery managers to monitor GPS locations of fishing activities to ensure vessels are complying with closed areas.
    • In Alaska, there are limits on the amount of halibut and crab that groundfish fisheries can incidentally catch. If the limit is reached, managers close the fishery for the remainder of the season.

The Science

Population Status

  • According to the 2017 stock assessment, rex sole in the Gulf of Alaska are not overfished and are not subject to overfishing.
  • In the Bering Sea/Aleutian Islands rex sole are managed under the “other flatfish complex”:      
    • This complex was last assessed in 2017, but data were insufficient to determine whether the complex is overfished.
    • An overfishing level is set for the complex and, as long as this level is not exceeded, the complex is not subject to overfishing. The complex is not subject to overfishing.
  • According to the 2013 stock assessment, rex sole on the West Coast are not overfished, and are not subject to overfishing based on 2016 catch data.

Location

  • Rex sole are found from central Baja California to the Bering Sea.  

Habitat

  • Rex sole live on sandy or muddy ocean bottoms.
  • They are found at depths between 100 and 200 meters and are found throughout the Gulf of Alaska. 
  • Along the coast of the Pacific Northwest they are found at depths of about 500 meters. 

Physical Description

  • Rex sole is a flatfish with both eyes located on the right side of its head.
  • They have small mouths with a blunt, rounded snout. Their body is oval, but elongated, and very slender.
  • The upper side of their body is light brown to gray in color and their underside is white. 

Biology

  • Rex sole are moderately long-lived (they can live for nearly 30 years), and can grow up to 23 inches.
  • Female rex sole grow faster and live longer than males. 
  • Depending on location, rex sole may reach maturity between 3.5 and 13 years.
  • Rex sole spawn from October through May. They are serial spawners, and will deposit eggs on more than one occasion throughout the spawning season. The spawning season may be longer in the Gulf of Alaska.
  • Eggs are fertilized near the sea bed, move into the water column, and require a few weeks to hatch. Once hatched, larvae spend about a year in the water column before settling to the bottom as juveniles.
  • Rex sole feed on shrimp, amphipods, and worms.
  • Sharks, skates, rays, lingcod, arrowtooth flounder, and some species of rockfish prey on rex sole. 

Last updated: 03/30/2018