Summer Flounder (Paralichtys dentatus)

• The stock is rebuilding and is expected to be fully rebuilt by January 1, 2013. Overfishing is not occurring and the stock is not overfished.
• Management measures, which include seasons, quotas, and size limits, are increasing population size.
• Flounder is a good, low-fat source of B vitamins and an excellent source of niacin. For more on nutrition, see Nutrition Facts. (USDA)
• Summer flounder has shown potential as an aquaculture species in recent studies between NOAA and the University of New Hampshire.

Sustainability Status

Biomass: Summer flounder biomass is 72% of the level need to support maximum sustainable yield (B_MSY).
Overfishing: No
Overfished: No
Fishing and habitat:Summer flounder are caught in bottom otter trawls and dredges, which may impact submerged aquatic vegetation.
Bycatch: Summer flounder bottom trawls can incidentally catch sea turtles. Since 1992, all vessels using bottom trawls for summer flounder off Virginia and North Carolina have been required to use NMFS-approved Turtle Excluder Devices (TEDs) in their nets. The fishery management plan for summer flounder also sets minimum mesh sizes to prevent other bycatch.
Aquaculture: Summer flounder has shown potential as an aquaculture species in recent studies between NOAA and the University of New Hampshire.

Science and Management

Summer flounder is managed as one stock from North Carolina to Maine. The stock is managed cooperatively by the Atlantic States Marine Fisheries Commission and the Mid-Atlantic Fishery Management Council through the Summer Flounder, Scup, and Black Sea Bass Fishery Management Plan. Managers have controlled the amount of summer flounder caught each year through a Total Allowable Landings (TAL) program since 1993. Catch is allocated into an annual commercial quota (60%) and recreational harvest limit (40%). Current management measures also include minimum sizes of fish, minimum mesh size requirements for trawls, permits and administrative fees for dealers and vessels, a moratorium on entry into the fishery, mandated use of sea samplers, monitoring of sea turtles in the southern part of the management unit, and collection of data and record keeping by dealers and processors.

Since 1993, summer flounder has been under a rebuilding plan that seeks to reduce fishing mortality (the amount of fish landed) and continue rebuilding the stock. A 10-year rebuilding plan began in 2000 and would have ended January 1, 2010; however, the Reauthorization of the Magnuson-Stevens Act extended the summer flounder rebuilding plan to January 1, 2013.

Life History and Habitat

Life history, including information on the habitat, growth, feeding, and reproduction of a species, is important because it affects how a fishery is managed. High reproductive potential in summer flounder means they may respond to management actions more rapidly than species that reproduce slowly and in small numbers.

• Geographic range: In the Atlantic Ocean from Nova Scotia to the northern Gulf of Mexico. They are most common from Cape Cod, Massachusetts, to Cape Hatteras, North Carolina.
• Habitat: Nursery grounds are located in coastal estuarine areas. Adults are concentrated in bays and estuaries from late spring through early autumn when they migrate offshore to the outer continental shelf. Summer flounder inhabit a variety of mud and sand substrates and may be found in marsh creeks, sea grass beds, and sand flats.
• Life span: Females live to at least 14 years, and males live to at least 12 years.
• Food: Larval and post larval flounder primarily feed on zooplankton (tiny floating animals) and small crustaceans. Juveniles include more fish in their diet. Adults are opportunistic feeders, eating whatever food is convenient at the time, and feed mostly on fish and crustaceans. Specific types of prey include windowpane and winter flounder, northern pipefish, Atlantic menhaden, bay anchovy, red and silver hake, scup, Atlantic silverside, American sand lance, bluefish, weakfish, mummichog, rock crabs, squids, shrimp, small bivalve and gastropod mollusks, small crustaceans, marine worms, and sand dollars.
• Growth rate: Fast; females grow faster than males
• Maximum size: Males can grow up to about 25 inches; females can grow up to about 36 inches.
• Reaches reproductive maturity: At age 2
• Reproduction: Females ranging from 14.4 to 27 inches total length (TL) have 0.46 to 4.19 million eggs. Summer flounder have a high egg production to body weight ratio; in fact, the weight of annual egg production is approximately 40 to 59% of the weight of spawning females. Summer flounder are serial spawners - they release their eggs in several batches throughout the spawning season. Eggs are pelagic (in the water column) and buoyant and hatch in waters of the continental shelf. Larvae are transported by prevailing water currents toward coastal areas where they complete their transformation.
• Spawning season: From September through February, depending on location
• Spawning grounds: Over open ocean areas of the continental shelf
• Migrations: Summer flounder migrate inshore and offshore seasonally in response to changes in water temperature. During winter and early spring, they are concentrated offshore in depths of 230 to 508.5 feet along the outer edge of the continental shelf, but in late spring and early summer, they move inshore and concentrate in shallow coastal waters and estuaries. Summer flounder migrate offshore in August of September.
• Predators: Larval and juvenile summer flounder are preyed upon until they grow large enough to fend for themselves; predators include spiny dogfish, goosefish (monkfish), cod, silver hake, red hake, spotted hake, sea raven, longhorn sculpin, and fourspot flounder. Predators for adults include large sharks, rays, and goosefish (monkfish).
• Commercial or recreational interest: Both
• Distinguishing characteristics: The bodies of summer flounder are laterally flattened, and both eyes are on the left side. Summer flounder are able to blend into their background by adapting to the texture and color of the substrate.

Role in the Ecosystem

Development of post larval and juvenile summer flounder occurs primarily within bays and estuarine areas, notably Pamlico Sound and Chesapeake Bay. Since this important stage in their life history takes place near areas of heavy human population, water quality is an important ecosystem consideration for summer flounder.

The timing of peak spawning in October/November coincides with the changes to temperature profiles in the Atlantic, as well as the time of highest productivity of autumn plankton. The combination of these elements give larval summer flounder improved chances of survival.

Summer flounder rely on a fairly mixed diet of fish and invertebrates through their life history and are especially vulnerable as prey during their larval stages. Juvenile summer flounder are opportunistic feeders, and their diet includes mysids, fish, and some crustaceans. There are gradual changes in the diet of summer flounder, with fish becoming more important as a food source as individuals get older and larger. Adults are also opportunistic feeders, with fish and crustaceans making up a significant portion of their diet.

Additional Information

As a demersal species, summer flounder occupy the same bottom habitats as several other commercial important species including scup, black sea bass, sea scallops, squid, and other flounders. Summer flounder are susceptible to being caught by bottom fishing gear throughout their range, especially trawl, sea scallop dredge, and pound nets. Management measures are in place to reduce bycatch of summer flounder, and ongoing research regarding gear modifications may further reduce bycatch in the future.

Market names: Flounder, Fluke
Vernacular names: Plaice, Northern fluke
Several other species are also marketed as Flounder. Southern flounder, Smalleye flounder, and European flounder are also marketed as Fluke.

Biomass

Biomass refers to the amount of summer flounder in the ocean. Scientists cannot collect and weigh every single fish to determine biomass, so they use models to estimate it instead. These biomass estimates can help determine if a stock is being fished too heavily or if it may be able to tolerate more fishing pressure. Managers can then make appropriate changes in the regulations of the fishery.

Summer flounder biomass reached record lows in the late 1980s and early 1990s. With improved recruitment and decreased fishing mortality, spawning stock biomass (SSB), which is a measure of the amount of reproductively mature fish, has increased substantially. As of a 2008 assessment, SSB was estimated to be 43,363 metric tons (95.6 million pounds) in 2007, about 72% of the peer-review SSB target of 60,074 metric tons (132.4 million pounds).

Note: Summer flounder biomass is presented as spawning stock biomass is the graph.

Landings

Landings refer to the amount of catch that is brought to land. Landings decreased around 1990 due to strict management measures put in place with the implementation of the Summer Flounder, Scup, and Black Sea Bass Fishery Management Plan (FMP).In 2007, reported landings for the commercial fishery were 4,489 metric tons, about 5% below the commercial quota.

Note: The landings presented are domestic commercial landings.

Biomass and Landings

Are landings and biomass related? Landings are dependent on biomass, management measures in the fishery, and fishing effort. Summer flounder has been under a rebuilding plan since 1993, which has been extended through 2013. With stricter management in place, the spawning stock biomass of summer flounder has increased.

Data sources:
Biomass and landings from 47th Northeast Regional Stock Assessment Workshop Assessment Summary Report

Important Dates

1979 – Total U.S. commercial landings of summer flounder peak at nearly 18,000 metric tons (40 million pounds)
1988 – Original FMP establishes a management plan for summer flounder
1993 – Amendment 2 establishes a rebuilding schedule, commercial quotas, recreational harvest limits, size limits, gear restrictions, permits, and reporting requirements for summer flounder; also creates the Summer Flounder Monitoring Committee
1999 – Amendment 12 revises FMP to comply with SFA and establishes framework adjustment process; also revises the overfishing definition for summer flounder.
2001 – Framework 1 establishes quota set-aside for research
2001 – Framework 2 establishes state-specific conservation equivalency measures
2004 – Framework 5 establishes multi-year specification setting of quota
2006 – Framework 6 establishes region-specific conservation equivalency measures
2008 – Stock status determination is modified

Notes and Links

General Information:
NMFS Northeast Fisheries Science Center Status of Fisheries Resources off the Northeastern U.S. Summer flounder species page

Atlantic States Marine Fisheries Commission (ASMFC)

NMFS Northeast Regional Office Current Bycatch Priorities and Implementation Plan (2005)

Special Report No. 78 of the ASMFC: Proceedings of the Summer Flounder Bycatch and Regulatory Discards Workshop (2003)

NOAA Technical Memorandum NFMS-NE-151: Essential Fish Habitat Source Document: Summer Flounder, Paralichthys dentatus, Life History and Habitat Characteristics (1999)

NOAA Technical Memorandum NMFS-SEFSC-307: Interactions between Sea Turtles and the Summer Flounder Trawl Fishery (1992)

Fishery Management:
Mid-Atlantic Fishery Management Council Summary of the history of the Summer Flounder, Scup, and Black Sea Bass Fishery Management Plan (FMP)

ASFMC FMP for Summer Flounder (1982)

2006 Review of the ASMFC FMP for Summer Flounder

Stock Assessments:
47th Northeast Regional Stock Assessment Workshop Assessment Summary Report