Winter Flounder: All you Need to Know

A winter flounder (Pseudopleuronectes americanus) is a species of flatfish found in the coastal waters of the western Atlantic Ocean, from Labrador to the Gulf of Mexico.

They are bottom-dwelling fish that are typically found in shallow, inshore waters. Winter flounder are known for their ability to change color to match their surroundings.

They are a popular ocean fish and are also caught commercially for food. Read on to learn more.

freshly caught flounder
Freshly Caught Flounder

Winter Flounder: Quick Facts

  • A female can lay up to 40 batches of eggs
  • They hatch within days of being successfully fertilized
  • A stunning transformation takes place shortly after hatching when the left eye migrates to join its twin on the right side of their head.
  • The small size of its mouth severely restricts the food it is able to consume.
  • It has special protein which helps protect it from any detrimental effects of the cold.
  • Its eyes are located on their right side while the summer flounder’s peepers can be found on its left.

Characteristics and Appearance

With its one-of-a-kind appearance, the winter flounder is quickly identifiable amongst other sea creatures. To learn more about this interesting creature’s physical characteristics, keep reading to discover what makes it unique!

Winter flounder have a uniform size, usually exceeding two feet in length, and can reach much bigger sizes.

On average, they weigh between four and five pounds; typically never growing to a size beyond this normal range.

The winter flounder’s stout, oval-shaped physique allows it to seamlessly conceal itself in coastal seagrasses and kelp thickets.

As a flatfish, winter flounder have an unmistakable shape that allows them to rest their left side on the seafloor. To capitalize on this specific anatomy, they are gifted with two eyes placed strategically on one side of the body. This heightens peripheral vision and optimize their ability to detect prey or predators.

They can be seen in a plethora of colors, from muddy brown to deep reds, with shades of olive and slate being the most popular. The upper side is usually black with small hints of lighter hues occasionally visible. These tantalizing gradients make these fish an incredible sight to behold!

To top off their beauty, the winter flounder’s underside is a stunning blend of white. Furthermore, its fins are adorned with shades of pink, red and even yellow. An exquisite combination that further demonstrates why these fish remain a favorite among many!

In comparison to other flounder species, they have an extraordinary ability. The capacity to blend in by variably changing their hue. Their range of colors is much more vivid than most fish of this kind.

winter flounder up close
Close Up

Lifespan and Reproduction

As compared to many other fish species, the winter flounder lives a reasonably lengthy life. With an average lifespan of 15-18 years, they can give you plenty of memories if allowed to thrive in their natural habitat!

As winter and spring approach, they make their way to shallow inshore waters where they spawned. Like all other sea creatures, these fish have an innate ability to find the areas of their birth for spawning. During a single session, female flounders can carry up to 1.5 million eggs!

During the spawning season, these creatures deposit their eggs on the ocean bed about 40 times. Upon hatching, they are known as larvae and eventually grow into flounders.

After around six weeks from the time of their birth, these larvae then travel to the seabed and commence transitioning into young adults.

Over time, their left eye will gradually transition to the right side of their body. Survival rates depend heavily on factors such as water temperature, condition, and salinity levels.

After undergoing the juvenile stage of development, winter flounders quickly become adults. In a span of two years or so, they transform from juveniles into fully mature flounders.


Winter flounder inhabit the Atlantic ocean along the eastern coast of North America, usually between North Carolina and Canada’s Gulf of St. Lawrence.

If you’re looking for winter flounder, head north of Delaware Bay. They can be found there in abundance there. Additionally, three main stocks exist along the Gulf of Maine and Georges Bank regions, as well as the Southern New England/Mid-Atlantic area.

They are well-adapted to the chilly waters of their habitat, and can stay close to shorelines that feature kelp or seagrass beds. These fish have an affinity for cold water; they will even thrive in temperatures below freezing! Their optimal temperature range is 32-50 degrees Fahrenheit.

To make it through the harsh cold of winter, these fish depend on a special protein that works as an “antifreeze” to protect them. Moreover, they remain still near the ocean floor while conserving energy and evading threats from predators.

cooked winter flounder
Ready to Eat

Food and Diet

Winter Flounder are ferocious, diurnal hunters that go after a wide variety of aquatic life. They generally choose fish and crustaceans over plant matter because they can spot their prey much more easily in the day.

Although technically omnivorous, these predators rarely turn down an opportunity to feast on other creatures!

During their larval stages, they rely mainly on plankton to sustain themselves. Consuming both phytoplankton and zooplankton as they grow ever larger.

As they mature, these juveniles start to devour larger prey items; however, plankton still makes up a significant portion of their diet.

As adults, winter flounder have relatively small mouths which limit what they can consume. Consequently, larger prey is spared from the fish’s jaws and instead winter flounder mainly feed on smaller invertebrates such as shrimps and plankton. Additionally, shellfish, tiny crabs and worms all make up their diet when available.

Winter flounder can feed on a variety of invertebrates, including young squid and octopus, as well as small mollusks. Depending on the specific habitat they inhabit, their dietary habits may vary.


During their adult stage, the winter flounder is faced with an array of predators such as the Atlantic cod, spiny dogfish and monkfish.

Unfortunately, juvenile flounder face a multitude of dangers. Striped bass, toadfish, and even other flounder are just some of the predators that prey on young fish. Aside from these aquatic creatures, birds and invertebrates also pose threats as do skates and many marine mammals.


The winter flounder is far from invincible, in fact it faces a multitude of threats throughout its life. Here are just some of the dangers they encounter.

Undeniably, humanity poses the most significant risk to winter flounder as their coastal habitat is prone to pollution.

They are highly prone to overfishing and their population has drastically diminished in a number of regions along the East Coast. To ensure proper protection for these species, numerous jurisdictions have initiated regulations restricting how they can be caught, such as requiring specific types of fishing equipment.

Global warming and climate change have had a devastating effect on winter flounder populations. These fish rely on cold waters to thrive, yet the oceans are becoming increasingly warmer – this poses a serious risk during spawning and reproduction seasons.

The changing temperature of the ocean affects not just fish, but also plankton – the primary food source for larvae and juveniles.

Unfortunately, human-produced waste often finds its way into their environment and can have catastrophic consequences. Oil spills are a prime example of how much destruction they may cause – wiping out whole colonies’ habitats in minutes.

flounders on boat
Flounder Gigging

Conservation Status of Winter Flounder

The winter flounder population is threatened by overfishing across many of its habitats. While the Georges Bank stock has been drastically diminished due to extensive overfishing, regulations have fortunately made a difference and are helping to keep these stocks in check.

Similarly, the Southern New England/Mid-Atlantic stock is exposed to overfishing. On the other hand, this is not a concern for the Gulf of Maine population as it does not suffer from any overfishing pressures.

Fortunately, the winter flounder population is large and plentiful in much of the North American east coast. There are no projections for their numbers to decline drastically anytime soon, nor have they been declared endangered or threatened.


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