Fluke Fish (Summer Flounder)

Quick Take

• Fluke fish are born looking like any other fish, but something strange happens to their face as they grow. Eye migration explained →
• This fish has a hunting strategy so effective it barely needs to move, a result that comes down to one unexpected adaptation. See the ambush strategy →
• Fluke fish were once in serious trouble, but then their population did something remarkable that caught scientists off guard. Explore the population rebound →
• Female fluke fish produce a staggering number of eggs, a quantity far greater than most people would guess for a fish this size. Discover the egg counts →

The fluke fish (also known as summer flounder, Northern fluke, and Hirame) is found in abundance across the United States’ eastern seaboard and is important for both commercial and recreational fishing purposes. 

Fluke Fish Facts 

• Rebounding populations: Between 1989 and 2003, the estimated biomass of fluke fish rebounded about tenfold off the U.S. Atlantic coast. Today, the NOAA rates the species as ‘not overfished.’ 
• “Chameleons of the sea:” The survival of fluke fish depends on camouflage and blending in with the ocean floor, so the fish has evolved the ability to change its color and texture to match its surroundings.
• Up to 4 million eggs: Many fish species spawn incredible amounts of eggs, and the fluke fish’s total can be quite impressive. Larger fluke females can spawn up to 4 million eggs.
• An odd-looking fish: If you’re thinking fluke fish look a bit different, it’s not just you. Flatfish have been called the “most asymmetrically-shaped vertebrates on Earth.” Born with eyes in a ‘normal’ position on the sides of their head, as a fluke fish grows, its right eye moves to the top of its head. This creates one of the more interesting-looking fish in the animal kingdom.

Classification and Scientific Name

The scientific name for fluke fish is Paralichthys dentatus. They’re also often called ‘summer flounder,’ but on the United States East Coast, they’re most commonly referred to as ‘fluke.’ 

Fluke fish are in the order Pleuronectiformes, of which there are 3 suborders, 7 families, 13 subfamilies, 117 genera, and 540 species.  This order is commonly grouped under the term ‘flatfishes.’ Their family is Paralichthyidae, which includes large-tooth flounders and contains approximately 110 species. 

The oldest fossils of flatfishes emerged shortly after the extinction of the dinosaurs in the Paleocene epoch (65 to 57 million years ago). 

Appearance

Fluke fish females can reach a size of about 3 feet in length and weigh more than 20 pounds. In 2007, a New Jersey fisherman caught a 24.3-pound fluke, although the official record still belongs to a 22.7-pound catch off Long Island in 1975. Due to their importance in commercial fishing, few individuals reach their maximum size. Like most fish, flukes experience dimorphism where females are larger than males. 

Like other ‘flatfish’ that have flat bodies and remain near the ocean’s floor, the fluke has brown coloring that matches the sea bottom. However, the species can also adjust their color to better match their surroundings and blend into their environment. Fluke fish also have spots on their back that can help distinguish the species.  

Distribution, Population, and Habitat

In 1989, the NOAA estimated fluke stock had dropped to a total biomass of 7,408 metric tons. By 2003, that number had rebounded all the way to 69,153 metric tons. The bottom line is that populations of the species have rebounded dramatically and today are considered ‘not overfished’ by the NOAA. 

The habitat of fluke varies by time of year. During colder months, fluke fish will move offshore to depths of up to 600 feet. During the spring and summer, fluke fish move into feeding grounds closer to shore that are also shared by juvenile fish. 

The fluke fish can be found from as far south as Florida and reaches as far north as the Canadian maritime provinces, such as Nova Scotia. In general, as fluke fish age, they tend to move into more northerly shallow feeding grounds. This leads to larger fluke fish often being caught in areas like New England, as these areas hold more fully grown individuals. 

Predators and Prey 

Fluke fish hunt by using their remarkable camouflage. The fish lie on the bottom of the sea, often burrowing into sand until only their eyes are exposed above the sand. When prey approaches, the flounder quickly emerges from hiding and strikes at prey, including crabs, squid, shrimp, forage fish such as anchovies, and even smaller flounders. 

As juveniles, fluke fish face several predators that inhabit shallow coastal waters. Bass, sharks, and toadfish will all hunt juvenile flounders. In addition, the species faces threats from other, larger bottom-dwellers such as monkfish, skate fish, and rays. 

Reproduction & Lifespan 

Spawning occurs during colder months — fall and winter — when the fish move offshore to water temperatures often between 33 and 50 degrees Fahrenheit. The colder conditions increase plankton biomass and give fluke fish larvae an improved chance of survival. Sexual maturity is reached by 3 years of age, with larger females releasing more eggs. It’s estimated that the largest flukes can release nearly four million eggs. As larvae mature, they follow ocean currents to inshore estuaries and other habitats where they continue developing. 

Like other flatfish, the larvae of fluke fish look quite different from their fully grown form. Their eyes look like those of many other fish, with one on each side of their head. As the fish grow, its left eye migrates to the top of its head, and its skull twists so its jaw lies perpendicular to its body. Fluke fish can live up to 14 years, but rarely live past 10. 

Fishing & Cooking

Fluke fish are an important fish for both commercial and recreational purposes. In 2026, the commercial quota for summer flounder is 12.78 million pounds, and the recreational harvest limit is 8.79 million pounds, with the allocation split approximately 59% commercial and 41% recreational.

Fishing for flukes is popular, as the fish move inshore during the summer months on Atlantic beaches in the United States.  They can be caught off piers, from the shore, or from a boat offshore.

The taste and texture of fluke fish are both considered mild. In addition, flukes are a lean fish. Per 100 grams, they have 91 calories, 1.2 grams of fat, and 18.8 grams of protein. The fish is often served simply, with lemon or butter.