Winter Flounder

About the Species

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

Status

• In U.S. waters, winter flounder is assessed and managed as three stocks: Georges Bank, Southern New England/Mid-Atlantic, and Gulf of Maine.
• The Georges Bank stock spawning stock biomass (a measure of the amount of winter flounder in the population that can reproduce) has been increasing since 2005. According to the 2017 stock assessment this stock is not overfished, remains in a rebuilding plan, and is not subject to overfishing.
• The Southern New England/Mid-Atlantic stock is still overfished, but not subject to overfishing according to the 2017 stock assessment. The original rebuilding plan was from 2004 to 2014. In May 2013, its target end date was extended to 2023.
• The Gulf of Maine stock is the smallest of the three winter flounder stocks. The results of the 2017 stock assessment were highly uncertain, and scientists were unable to determine an abundance estimate for this stock. However, they were able to determine that the stock is not subject to overfishing.

Appearance

• Winter flounder have an oval shape and a thick body.
• Their eyes are on the right side of their body.
• They have a straight lateral line and dark coloring.
• Their coloring often varies with their habitat, ranging from muddy to slightly reddish brown, olive green, or dark slate, to an almost black upper side.
• Their underside is white, and their dorsal and anal fins are often tinged with pink, red, or yellow.

Biology

• Winter flounder live 15 to 18 years and grow to more than 2 feet in length.
• They spawn during the winter and spring in shallow inshore waters, often returning to the same areas where they were born to spawn.
• Females usually produce between 500,000 and 1.5 million eggs.
• They deposit their eggs on sandy bottoms and algal mats at night, usually about 40 times every spawning season.
• Newly hatched larvae have one eye on each side of the head.
• Five to six weeks after they hatch, larvae settle to the bottom to begin their transformation into juveniles.
• After weeks of adapting to living on the bottom, their left eye migrates to the right side of their body and their metamorphosis is complete.
• The growth and survival rates of larvae and juveniles depend on several factors, including temperature, salinity, water quality, and the availability of food.
• Winter flounder feed during the day because they depend on sight to locate prey.
• Their small mouths limit what they can eat.
• They feed on small invertebrates, shrimp, clams, and worms.
• Fish (mainly striped bass, bluefish, toadfish, and summer flounder), birds, invertebrates, winter skate, and marine mammals prey on larval and juvenile winter flounder.
• Atlantic cod, spiny dogfish, and monkfish prey on adults.

Where They Live

• Winter flounder are found in estuaries and on the continental shelf of the Northwest Atlantic, from the Gulf of St. Lawrence, Canada to North Carolina. They are most common north of Delaware Bay.

Management

• There are three stocks of winter flounder in U.S. waters, the Gulf of Maine, Georges Bank, and Southern New England/Mid-Atlantic stocks.
• NOAA Fisheries and the New England Fishery Management Council manage the fishery in federal waters. The Atlantic States Marine Fisheries Commission coordinates management of winter flounder in state waters (0 to 3 miles offshore).
• Winter flounder, along with other groundfish in New England waters, are managed under the Northeast Multispecies Fishery Management Plan, which includes:
  • Permitting requirements for commercial vessels.
  • Separate management measures for recreational vessels.
  • Time/Area Closures to protect spawning fish and habitat.
  • Minimum fish sizes to prevent harvest of juvenile fish.
  • Annual catch limits, based on best available science.
  • An optional sector (catch share) program can be used for winter flounder and other groundfish species. The sector program allows fishermen to form harvesting cooperatives and work together to decide when, where, and how they harvest fish.