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Winter Flounder: 
(Pseudopleuronectes americanus)










  • According to the most recent assessment (2011), winter flounder stocks are rebuilding.
  • New measures were recently put in place to end overfishing and continue to rebuild overfished groundfish stocks like winter flounder (and maintain healthy ones). Under these new measures, no commercial fishing vessel is permitted to harvest Southern New England winter flounder in order to protect this vulnerable stock.
  • Flounder is a good, low-fat source of B vitamins and an excellent source of niacin. For more on nutrition, see Nutrition Facts. (USDA)
  • Winter flounder are one of the five flounders most commonly found on dinner tables.


Life History and Habitat of the Winter Flounder:
Life history, including information on the habitat, growth, feeding, and reproduction of a species, is important because it affects how a fishery is managed.

  • Geographic range: In the Northwest Atlantic from Labrador to Chesapeake Bay.
  • Habitat: Young-of-the-year (fish born in the past year) and some one year-old fish remain in the estuaries where they were hatched throughout the year. Juveniles prefer sand or sand-silt bottoms in a wide range of salinity and temperature. Adults occupy bottom habitats in inshore bays and estuaries during the winter and deeper water in the summer. While inshore, adults prefer muddy sand, clean sand, clay, and pebbly or gravelly ground.
  • Life span: 15 to 20 years.
  • Food: Adults feed on small invertebrates, shrimp, clams, and worms.
  • Growth rate: Growth varies by stock – Georges Bank winter flounder grow the most quickly, and Gulf of Maine grow the most slowly.
  • Maximum size: Up to 1.9 feet total length. Georges Bank winter flounder are the largest; Gulf of Maine are the smallest.
  • Reaches reproductive maturity: Varies by stock – Georges Bank winter flounder mature at the earliest age and smallest size, and Gulf of Maine mature at the oldest age and largest size.
  • Reproduction: Females usually produce between 500,000 and 1.5 million eggs, but up to 3.3 million eggs have been reported. Females deposit eggs on sandy bottoms and algal mats at night. This event occurs an average of 40 times per spawning season. Proper temperature and salinity are critical to the survival of eggs during larval development. Five to six weeks after hatching, larvae settle to the bottom to begin metamorphosis. After eight weeks, their left eye migrates to the right side of their body and metamorphosis is complete.
  • Spawning season: During the winter and spring.
  • Spawning grounds: In shallow inshore waters. Adults tend to return to the same spawning grounds every year.
  • Migrations: Every January, winter flounder migrate from offshore areas where they feed to inshore areas where they spawn.
  • Predators: Fish, such as striped bass, bluefish, toadfish, and summer flounder, birds, invertebrates, winter skate, and marine mammals prey on larvae and juveniles. Atlantic cod, spiny dogfish, and monkfish prey on adults. Smooth dogfish, hakes, sea raven, striped sea robin, striped bass, bluefish, and wrymouth also eat adults but in smaller amounts.
  • Commercial or recreational interest: Both
  • Distinguishing characteristics: Winter flounder have eyes on the right side of the body, a straight lateral line, and dark coloring. Their coloring often varies with habitat; it ranges from muddy to slightly reddish brown, olive green, or dark slate, to an almost black upper. Their underside is white, and their dorsal and anal fins are often tinged with pink, red, or yellow on the eyed side.





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