American Oceans

Southern Flounder

Southern Flounder, also known by their scientific name Paralichthys lethostigma, are flatfish that primarily inhabit the coastal waters of the Gulf of Mexico.

Southern Flounder or Paralichthys lethostigma flatfish underwater

Although most people see Southern Flounder in the southern states, they also appear on the eastern seaboard.

The Southern Flounder is a flatfish that lays on its side to swim. Instead of swimming with its pectoral fins to propel itself, Southern Flounder use their powerful tail fin to move. Southern Flounder are ambush predators, lying in wait until their prey comes close.

Characteristics & Appearance

Southern Flounder are fascinating creatures, but they don’t have many physical variations from each other, meaning they look very similar to one another.

Weight & Length

Adult Southern Flounder are usually between 15 and 18 inches long, from the tip of their tail to the end of their head. Females grow larger than males, sometimes growing bigger than 25 inches.

On average, adult Southern Flounder weigh 5 pounds, although larger fishes weigh significantly more, up to 20 pounds. Female fish tend to weigh more than male fish due to their size.

Physical Characteristics & Color

Southern Flounder are oval-shaped, and they look like a standard fish that someone has flattened. Flounder are generally flat because they have evolved to lay on the ocean floor to disguise themselves in their surroundings.

When Southern Flounder lay in wait on the ocean floor, they have one side ‘up,’ that faces the top of the ocean, and one side ‘down’ that looks towards the ground.

For Southern Flounder, their left side is always up. Both of their eyes are on their left side, which allows them to see their surroundings.

Southern Flounder have a unique color pattern that helps them blend in with their surroundings. The color patterns are only on their left side because they always lay with that side exposed. The other side is usually a solid color.

The flounder’s left side is much more colorful. Southern Flounder are usually brown, tan, or beige colored with spots covering their body.

The markings can be brown, black, or even cream color. The flecks help Southern Flounder bend into their environments. 

Lifespan & Reproduction

Male and female Southern Flounder have vastly different lifespans. Female Southern Flounder grow and mature approximately three times as fast as the males. Interestingly, female Southern Flounder tend to live longer as well.

Male and female Southern Flounder take approximately two years to reach sexual maturity. At that stage, the males weigh about half what the females weigh. Males live for about five years, while females live until about eight years old.

Southern Flounder reproduce via fertilized eggs. Most spawning occurs in the months between November and February.

Female Southern Flounder release up to 45,000 eggs per pound throughout the spawning period.

Southern Flounder use a method of reproduction known as ‘broadcast spawning.’ Once the female releases her eggs, the male releases milt into the water to fertilize them. This method allows the fish to increase their chance of successful fertilization.


Southern Flounder generally inhabit coastal areas, such as embayments, estuaries, brackish ponds, and other shallow areas.

People mostly find them in either sandy or muddy areas along the bottom of the water. These areas provide good camouflage. 

When mating, Southern Flounder move from these areas to deeper waters. Some Southern Flounder have even been found in freshwater rivers and lakes, although these are much less common.

Where Do Southern Flounder Live?

Southern Flounder live in areas where they can utilize their camouflage when hunting their prey. That’s why they spend significant time in muddy waters, such as river estuaries or coastal areas. The cloudy water provides cover for attacks on other animals. 

They live in waters from South Carolina to the coast of Mexico. One area they don’t reside in is the southern tip of Florida, which could be due to predators or a lack of habitat.

Flounder rarely move into deeper water, aside from mating season, between November and February. 

Food & Diet

Southern Flounder are ambush predators. They lay in wait and eat whatever smaller animal is unlucky enough to swim or crawl past.

Southern Flounder are carnivores, meaning they only eat meat. They generally don’t discriminate when it comes to food, eating almost anything that comes their way. 

What Do Southern Flounder Eat?

Southern Flounder have a diet consisting of small fish and invertebrates like crabs and shrimp. Southern Flounder are opportunistic predators, meaning they eat whatever is in their vicinity. Juvenile flounder are known to be cannibalistic, too.

small crabs for Southern Flounder to eat

Southern Flounder blend into their surroundings and wait until their prey passes them. When they sense food around them, Southern Flounder use their powerful tail fin to propel themselves with a burst of speed. They then catch and eat their prey. 

Most of the food sources Southern Flounder consume live in the same coastal areas as Southern Flounder.

Crabs and shrimp often inhabit the coastal areas, which means they live near Southern Flounder. Small fish like to roam the same areas because they have access to food.

small shrimp for Southern Flounder to eat

Southern Flounder have strong, cone-shaped teeth on their top and bottom jaws. These teeth are suitable for catching prey and breaking down their flesh. The teeth are sharp, which makes grabbing and holding onto prey easier.

Southern Flounder use their teeth to ambush prey. With both eyes pointing upwards, they have excellent sight to sense prey that may swim near. They can also sense any disruptions in the sand. These sensations help guide their attack.

Threats & Predators

Although Southern Flounder aren’t threatened, people and other predators still significantly impact their lives and populations.

Human Threats

Humans form the primary threat to Southern Flounder for two primary reasons. The first is overfishing. Southern Flounder are a type of fish people enjoy eating.

But when people enjoy eating fish, they often take too much, impacting the remaining population levels.

The other impact comes with the industrial destruction of their habitats. As people use the coastal lands that these fish once called home, we continually destroy their habitat. A destroyed habitat can mean a lack of food, which can cause these animals to migrate or die.

Climate Change & Global Warming

Climate change and global warming put pressure on Southern Flounder populations because of their proximity to the coast.

As global warming increases sea level, the flounder must move into new areas that may or may not have sufficient prey for them to thrive.


Aside from humans, the Southern Flounder’s greatest predators include sharks, eels, and other large predatory fish like marlins.

Since Southern Flounder are medium-sized fish, only larger fish can consume them. Their coloring also helps keep predators at bay by allowing them to blend into their surroundings.

Other Threats

Although Southern Flounder don’t have many natural threats in adulthood, they have other threats. Southern Flounder eggs float.

Sometimes, other fish and birds will consume these eggs during spawning, causing fewer Southern Flounder to be born.

Conservation Status

Southern Flounder are not close to extinction. The ‘near threatened’ conservation status is only one level higher than ‘least concern.’

But just because Southern Flounder aren’t close to being extinct doesn’t mean we shouldn’t do anything to help them.

By reducing our impact on the climate, we can ensure that Southern Flounder are around for a long time.

Fun Facts About Southern Flounder

Southern Flounder is an all-around fascinating fish. Here are some fun facts about the Southern Flounder:

  • Southern Flounder are 15 inches long an average, but they’re only half as wide as they are long
  • Southern Flounder have both eyes on their left side to help them see when they lay flat on the ocean floor
  • Southern Flounder inhabit the coastal waters of the U.S. south except for Florida, which is a problem scientists are still figuring out
  • Southern Flounder area white fish that people say tastes slightly sweet
  • Southern Flounder are generally nocturnal
  • Southern Flounder are known to partially bury themselves for more effective hunting

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