Summer flounder.
Summer flounder.
Courtesy: Marine Biological Laboratory, Woods Hole, MA

Summer Flounder (Paralichthys dentatus)

Alternate common name: Fluke
Color: Changes with bottom color, ranges from all shades of brown to gray green to almost black. Underside is generally white, although spotting of pigment can occur.
Size: 14 to 37 inches long.
Habitat: Shallow coastal waters with sandy or muddy bottom, eelgrass, and dock pilings.
Seasonal appearance: May to November.


The summer flounder is the largest species of flatfish in Rhode Island waters. Often called fluke, these fish have both eyes on the same side of the body. The left side of the summer flounder is scaled and colored, and both eyes are on this side. Its right side has no eyes or scales and is white or translucent in color. Summer flounder can be distinguished from other flounder species by their large mouths, pronounced jaw, sharp teeth, two identical narrow ventral fins, and at least five dark spots arranged in an "X" on the back.

Critter Fact Species of flounder with both eyes on the left side of their bodies are known as "left-eyed" flounder.

Life History and Behavior

Summer flounder spawn in the spring or fall seasons, but never in the winter. They spawn along the Atlantic continental shelf, and the young migrate into coastal estuaries, such as Narragansett Bay, after their first year. Summer flounder larvae look remarkably like most other developing finfish, swimming upright in the planktonic zone with one eye on each side of the body. During the early life stages of development, the summer flounder's right eye migrates to the other side of the head next to its left eye, while the mouth stays in the original position. Following eye migration, also referred to as metamorphosis, the larvae settle to the bottom.

Summer flounder spend most of their lives close to or on the ocean floor. These fish scatter quickly when disturbed, propelling themselves out of their sandy hiding spots. They are fierce, aggressive hunters, and camouflage themselves to ambush prey by flipping sand over their backs. Summer flounder feed on fish, squid, crabs, sand shrimp, mollusks, and worms.

Fishery Note The Mid-Atlantic Fishery Management Council and the Atlantic States Marine Fisheries Commission manage the summer flounder fishery for conservation of the species and longevity of the fishery.

Special Notes

Adapted from The Uncommon Guide to Common Life on Narragansett Bay. Save The Bay, 1998.