Dover Sole

Dover sole image

Microstomus pacificus

ALSO KNOWN AS:

    Sole

SOURCE:

    U.S. wild-caught from Alaska to California
 

STATUS

  • POPULATION
  • FISHING RATE
  • HABITAT IMPACTS
  • BYCATCH
 

Click the icons to learn more about each criteria

 
 

OVERVIEW

Dover sole

The Dover sole's coloring helps the fish camouflage itself on the muddy ocean floor.

LAUNCH GALLERY

Not to be confused with European Dover sole, Pacific Dover sole is not a true sole and is related more closely to flounder. A mild-tasting fish, Dover sole has been harvested off the West Coast since World War II. Today, most U.S.-caught Dover sole is harvested by trawlers over sandy, muddy bottoms off Oregon, California, and Washington. A small amount is also harvested in the Gulf of Alaska.

Since groundfish are often caught together, harvests of more abundant species such as Dover sole have been limited in order to rebuild the species that are still overfished. In early 2011, managers implemented a “catch share program” for the West Coast groundfish trawl fishery to address this issue. Under this program, managers divide the annual catch limit for the fishery into shares controlled by fishermen. Fishermen can catch their share whenever they want, allowing them the flexibility to better plan their season, fish during safer weather and when market prices for their catch are highest, and reduce bycatch of overfished species.

Looking Ahead

Bycatch limits on petrale sole, an overfished groundfish species, have significantly limited catch of Dover sole. However, due to above average petrale sole reproduction and survival rates in the past few years, as well as overall productivity of flatfish stocks, managers slightly increased petrale sole bycatch limits for 2012. Furthermore, petrale sole populations are on target to be declared no longer overfished and rebuilt in 2013. As a result, current 2012 catch limits could be more than doubled in the 2013–2014 management cycle and fishing season. The successful rebuilding of the petrale resource should have a positive effect on the Dover sole fishery.

 
 
 

LOCATION & HABITAT

Dover sole is found in the Pacific Ocean from the Bering Sea and western Aleutian Islands to southern Baja California. They live near the ocean floor and prefer soft bottom habitat in waters 7 to 4,500 feet deep. Dover sole travel to deeper water as they age. Older females migrate seasonally from deep water on the outer continental shelf and upper slope where they spawn, to shallower water mid-shelf in the summer to feed. Older males also migrate seasonally but to a lesser extent.

 
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BIOLOGY

Dover sole spawn near the ocean floor from January to August in the Gulf of Alaska, from November to April off Oregon and California, and from January to March in Puget Sound. Dover sole typically spawn in offshore waters deeper than 1,440 feet. They spawn multiple times in a single spawning season, but primarily in winter. Female Dover sole produce relatively few large eggs (around 52,000 to 266,000 eggs as large as 0.1 inches), whereas petrale sole may produce up to 1.5 million smaller eggs at only 0.045 inches in diameter. Dover sole eggs are fertilized externally and are found in the upper part of the water column. These large eggs are dispersed and drift with the currents for many months. Once hatched, larvae settle in deeper water then travel inshore to find a suitable nursery area. Dover sole larvae usually settle to the bottom after a year of living in the upper water column, but some remain larvae for as long as 2 years—one of longest larval stages for any flatfish species. Scientists believe these “holdover” larvae delay settling to the bottom due to unfavorable environmental conditions, a characteristic common in some invertebrates but not observed in other fish species. Female Dover sole grow faster and larger than males, but males live longer. Females grow up to 2 feet 6 inches long, about 2 to 4 inches longer than males. Males can live up to 58 years, about 5 years longer than females.

Dover sole feed during the daytime by sight and smell. Their small mouths are well adapted for feeding on small invertebrates that live within the sediment. They also eat detritus as well as invertebrates that live at the sediment surface. Specifically, larval Dover sole eat copepods (small crustaceans), eggs, and nauplii (larval crustaceans), as well as other plankton (tiny floating plants and animals). Juveniles and adults feed on polychaete worms, bivalves, brittlestars, and small bottom-dwelling crustaceans. Seabirds and fish that live near the surface—such as albacore, jack mackerel, and tuna—prey on larval Dover sole. Sharks, bottom-feeding marine mammals, Pacific cod, arrowtooth flounder, and sometimes sablefish feed on juveniles and adults.

 
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PHYSICAL DESCRIPTION

Dover sole is a flatfish. Both of its eyes are located on one side of its head. They have a small mouth relative to their size. Their drab coloring helps them camouflage themselves on the ocean floor. In some areas, Dover sole are referred to as “slippery sole” because juvenile and adult Dover sole excrete mucous onto their skin/scales, making them incredibly slippery and hard to pick up or hold.

 
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OVERVIEW

Scientists from NOAA’s Alaska Fisheries Science Center survey Dover sole in the Gulf of Alaska every two years. Off the West Coast, NOAA’s Northwest Fisheries Science Center scientists conduct annual bottom trawl surveys that collect data on Dover sole abundance and the size and age of the fish in the population. Both science centers also run observer programs for the West Coast and Alaska groundfish fisheries. These programs place fisheries observers on commercial fishing vessels to monitor and record catch and critical biological data (such as fish age, reproduction, length, sex, and weight). This information improves our understanding of fishing activities and helps provide accurate accounts of total catch, bycatch, and discards associated with different fisheries and fish stocks.

 
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POPULATION STATUS

Spawning biomass refers to the amount of fish in the population that are able to reproduce. According to the latest assessment (2011), estimates of Dover sole spawning biomass off the West Coast is more than 469,000 metric tons, or almost 84 percent of the historical unfished spawning biomass (the amount with no fishing).

In Alaska Dover sole are managed under two flatfish complexes—the Gulf of Alaska Deep-water Flatfish Complex and the Bering Sea/Aleutian Islands Other Flatfish Complex. These complexes were last assessed in 2013 and are not currently overfished or experiencing overfishing.

 
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ADDITIONAL RESEARCH

The coastal states and treaty tribes conduct port-side monitoring programs that provide valuable biological data to support stock assessment science and aid in proper management decisions.

 
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Harvesting Dover Sole

Most U.S.-caught Dover sole is harvested in the West Coast groundfish trawl fishery. A small amount of Dover sole is also harvested by trawlers in the Gulf of Alaska.

Bottom trawls cause minimal damage when targeting Dover sole over soft bottoms off the West Coast and Gulf of Alaska. West Coast bottom trawl fisheries are highly regulated under a trawl catch share program, which encourages responsible fishing practices. Management measures also prohibit bottom trawling in certain areas to protect groundfish habitat and overfished species. Vessels use a vessel monitoring system which allows enforcement staff and fishery managers to monitor GPS locations of fishing activities and ensure that vessels are complying with closure areas.

In Alaska fisheries, there are limits on the amount of halibut that groundfish fisheries can incidentally catch. If the limit is reached, managers close the fishery for the remainder of the season. Off the West Coast, Dover sole are mostly caught as part of a deepwater complex that includes two species of thornyhead rockfish and sablefish. Bycatch is closely monitored under the groundfish trawl catch share program.

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Management

Who’s in charge? NOAA Fisheries and the Pacific (West Coast) and North Pacific (Alaska) Fishery Management Councils
Current management:
West Coast: Groundfish Fishery Management Plan (Dover sole are often caught in “multispecies complexes” – several different groundfish species caught together at the same time – and managed along with 90 other species that also live on or near the bottom.)

  • All vessels fishing in the groundfish fishery off Washington, Oregon, and California must have a federal limited entry permit. With a small number of permits available (about 400), this program controls the capacity of the groundfish fishing fleet by limiting the overall number of fishing vessels, the number of vessels using each of the three specified gear types (trawl, trap/pot, longline), and increases in harvest size by limiting vessel length.
  • As of January 2011, the West Coast groundfish trawl fishery is now managed under a trawl rationalization catch share program. Under this new program, managers establish annual catch limits based on the health of each fish stock. They then allocate a share of this catch limit to individual fishermen or groups of fishermen. 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. Observers monitor 100 percent of the fishing trips, which helps reduce bycatch and provides better data for future stock assessments.
  • Various gear restrictions and closed areas affect both West Coast groundfish fisheries and fisheries that may take groundfish incidentally. These regulations are in place to reduce bycatch of overfished groundfish species and protect groundfish habitat.

Gulf of Alaska: Gulf of Alaska Groundfish Fishery Management Plan (Dover sole are managed as part of the “deep water flatfish group” along with Greenland turbot and deep-sea sole, but the fishery primarily targets Dover sole.) Bering Sea/Aleutian Islands Groundfish Fishery Management Plan (Dover sole are managed as part of the “other flatfish complex”.)

  • Managers set a conservative annual catch limit for the fishery, which has allowed for sustainable harvests for the past decade.
  • A “license limitation program” limits the number, size, and specific operation of vessels in groundfish fisheries. This helps prevent the “race for fish,” where fishermen would compete against one another to catch as many fish before the catch limit was reached and the fishery closed, leading to unsafe fishing practices, market instability, and high levels of bycatch.
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Annual Harvest

Off the West Coast, Dover sole have been harvested by trawlers since World War II, and caught incidentally before then in directed fisheries for English and petrale sole. Annual landings have averaged more than 8,200 metric tons (18.1 million pounds) since 2001 on the West Coast. In 2012 more than 15 million pounds of Dover sole were harvested off the West Coast.

In the Gulf of Alaska, catch of Dover sole rapidly increased to almost 10,000 metric tons in the early 1990s when the domestic commercial fishery began, but has declined since then. Since 2001, annual catches have averaged about 550 metric tons. The 2013 catch totaled 173 metric tons. Overall flatfish landings are typically limited by early closures of the fishery, when they reach their quota of allowed Pacific halibut bycatch.

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Economy

Dover sole make up a substantial portion of annual revenues from the West Coast trawl fishery. In 2009, Dover sole landings were valued at $8.7 million, 2010 landings were valued at $7 million, 2011 landings were valued at $6.9 million, and 2012 landings were valued at more than $6.5 million.

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OVERVIEW

Dover sole harvested off the West Coast and Alaska is not the same fish as European Dover sole (Solea vulgaris), a premier whitefish that has been the mainstay of the European seafood scene for generations. (Seafood Business, 2011)

 
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SEASONAL AVAILABILITY

Year-round

 
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NUTRITION

Dover sole is an excellent source of low-fat protein, calcium, and other important nutrients.

Servings 1
Serving Weight 100 g (raw)
Calories 91
Protein 18.84 g
Fat, total 1.19 g
Saturated fatty acids, total 0.283 g
Carbohydrate 0 g
Sugars, total 0 g
Fiber, total dietary 0 g
Cholesterol 48 mg
Selenium 32.7 mcg
Sodium 81 mg

Dover sole table of nutrition

 
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