American Oceans

American Plaice

American plaice (hippoglossoides platessoides) are a species of flatfish that live in the Atlantic ocean, off the coasts of Canada and the United States.

American Plaice or hippoglossoides platessoides flatfish in ocean

They can survive in deep water but often live on continental shelves (which are the areas surrounding landmasses, where the water is shallower). They also usually stay in approximately the same area for their entire lifespans.

Characteristics and Appearance

Plaice are considered to be flatfish, which means that they swim on their sides. While most fish swim upright, with their fins perpendicular to the ocean floor.

Weight and Length

The American plaice grows slowly throughout its lifetime – a plaice that is less than a year old will most likely only have grown a few inches.

American Plaice or Hippoglossoides platessoides closeup length

Their environment is a major influence on their size. Size is also determined by water temperature and when in the year they hatch.

Between the first and second years of life, the American Plaice hits a growth spurt, and can reach 9 to 11 inches in length. The females grow faster than males. At their full adult size, they’re between 28 to 32 inches.

Within their first year, they weigh well under 1 pound. Their weight increases accordingly with their length, reaching approximately 14 pounds.

Physical Appearance and Color

Their eyes are both located on one side of their body; they swim with that side facing the surface of the water.

American Plaice body grayish brown color

On their “top” side, they’re usually a red or grayish brown, depending on their environment. Their “bottom” side is usually much lighter– white or very pale blue.

Lifespan and Reproduction

Due to their relatively slow-growing process, plaice usually aren’t considered fully mature until they’re around four years old.

When they do reproduce, they lay eggs in the spring– at some point between March and May. During the spawning season, females will lay 30,000-60,000 eggs.

The entire reproductive process greatly depends on their environment and the temperature of the water they live in.

Egg incubation usually lasts about two weeks, but this period increases or decreases according to water temperature.

Interestingly, when they first hatch, they resemble a “normal” fish– swimming perpendicularly to the ocean floor, and facing forward.

When the eggs first hatch, they do so near the surface of the water, and as they continue development the newly-hatched fish descend to the bottom.

During the time they’re descending, their bodies develop to resemble the adult form of the plaice– flat, with eyes on one side.

This time in their lives is critical to their future development. If they develop with their eyes on the wrong side of their body– facing the ocean floor instead of the surface– they will not survive.

This makes it impossible for them to navigate and avoid predators. Their lifespan ranges between 15 and 20 years.


Flatfish swim close to the bottom of the ocean and remain there for the entirety of their lives.

They’re found in areas where the bottom is sandy or muddy, rather than rocky, and they live at a depth of 120-600 feet.

Where Do American Plaice Live?

Plaice live in the Atlantic ocean, off the east coast of North America. They’re located in colder waters, sticking to the northeast region of the continent.

They rarely live anywhere further south than Rhode Island, and generally live no further North than the Labrador coast of Canada.

Spawning occurs somewhere around the Gulf of Maine, where conditions are ideal for their reproduction and early development.

Food & Diet

What Do American Plaice Eat?

Because the American plaice is a flatfish, they live on the ocean floor and don’t venture too far away from the area. That means they eat food that also lives by the ocean floor.

Some of the foods they’re most fond of include the brittle star (a type of starfish), capelin (a small silverfish), and sand lance (which are sometimes referred to as ‘sand eels’, although they are not eels).

All of these live near the ocean floor and are relatively easy for the plaice to catch. Like most fish, the American plaice don’t sleep, at least not in the way that we do.

They don’t adhere to a solid schedule and tend to feed around the clock. Their mealtimes depend on their food schedules.

All three of their favorite foods tend to be most active at night, so most of the American plaice’s eating takes place between 6 p.m. and midnight.

Their eating habits depend on the time of year, too: they eat a lot in April and throughout the summer, but in the fall and winter when the water is a lot colder, they eat much less. This is probably because their food sources are more plentiful during spring and summer. 

Threats & Predators

The American plaice doesn’t face as many threats as other, less hardy species of fish. Part of this is due to their appearance: flatfish, true to their name, live close to the ocean floor, and their coloring blends into their environment, making them difficult to spot.

Human Threats

Humans probably pose the largest threat to the population of American plaice. Overfishing has the potential to greatly affect their population, although there are plenty of rules in place to prevent this from happening.

To maintain population sizes, they are monitored by the NOAA (National Oceanic and Atmospheric Administration).

Commercial fishing of the plaice may only occur at certain times of the year, to avoid interference with reproduction and spawning.

Climate Change & Global Warming

Because the development of the American plaice is closely tied to water temperature, they can be greatly affected by temperature change. When the water is abnormally cold, they move toward the south and slightly warmer waters.

However, they also cannot exist in waters that are too warm, so climate change and the subsequent rising ocean temperature are harming plaice populations.


Plaice are most vulnerable to predators during the early stages of their lives. The period between hatching and full maturity– about the first four years– is when they’re small enough to be targeted by predators like sharks and eels.

As they reach maturity, their appearance helps to hide them from predators. However, humans eat plaice– their largest predator is probably humans and commercial fishing.

Other Threats

Plaice don’t face a particularly large number of threats throughout their lives, aside from humans and climate change.

They do pose a threat, however, to smaller sea organisms– they eat crabs, shrimp, squid, and smaller fish. During the earliest phases of their lives, they eat algae and plankton.

Conservation Status

The conservation status of the American plaice differs between the United States and Canada.

In the United States, they are at the very lowest threat level, LC or “Least Concerned”. In Canada, however, they are considered threatened due to commercial overfishing.

Overfishing in Canada is considered to be permanent, with complete population recovery unlikely or impossible.

Fun Facts

  • The American plaice hunts all of the time– regardless of the time of day, season, weather, or temperature. They’re always on the prowl for something to eat.
  • When threatened, they hide in the sand at the bottom of the ocean. Their coloring helps them avoid detection by predators.
  • Humans eat plaice because of their similarity in flavor to the sole, lemon sole, and halibut. Their meat is pure white and is very delicate and flavorful.
  • American plaice has a European counterpart, fittingly referred to as the European plaice. These are usually smaller than their American cousins, with rougher skin and larger scales.

Add comment