Summer Flounder
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Ocean Fishes

Summer Flounder

Paralichthys dentatus

Distribution

Temperate latitudes along the eastern coast of North America

Ecosystem/Habitat

Seagrass beds and offshore soft bottoms

Feeding Habits

Ambush predator

Conservation Status

Least Concern

Taxonomy

Order Pleuronectiformes (flatfishes), Family Paralichthyidae (sand flounders)

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The summer flounder is a flatfish that lives off the east coast of North America from Florida to Canada. It lives in nearly constant contact with the seafloor and prefers muddy or sandy soft bottoms. This species tolerates a wide range of depths and can be observed or captured from estuaries (and even lowland rivers) to depths of more than 500 feet (150 m). Summer flounder can be fairly large, with individuals growing to three feet long (~1 m). This species gets its common name from its tendency to migrate to nearshore waters during the spring and summer and to offshore waters during the fall and winter. When fishers concentrated their efforts near shore, the summer flounder was the most common flounder during the summer.

Like all flatfishes, summer flounder have both of their eyes on the same side of their heads, and they live on the seafloor, lying on their blind side, with their eyes facing the open water column. This species is one of several “sand flounders,” with both eyes on the left side of the head. Amazingly, when they hatch from their eggs, summer flounder resemble normal fishes, with an eye on each side of the head. As they mature, the bones on the right side of the skull grow significantly faster than on the left side, so the right eye and nostril slowly migrate to the left side. The jaws, however, do not change significantly, so the adults bite sideways, from left to right.

Summer flounder are active predators that mostly eat a variety of bony fishes but occasionally also benthic invertebrates, including crabs, shrimps, and squids. This species uses two distinct strategies when feeding. It can either utilize its incredible ability to blend in with the bottom and ambush potential prey, or it can utilize its exceptional swimming ability to actively chase faster moving prey. Their camouflage is also used to avoid predation.

Reproduction occurs in deeper, offshore waters during the colder months. They spawn by a method known as broadcast spawning, where females and males release their eggs and sperm into the water column at the same time. This method increases the likelihood that the eggs will become fertilized and decreases the chances that fertilized eggs will be eaten by egg predators near the seafloor.

There is a large commercial fishery for the summer flounder, but this species is not overfished and is therefore not threatened by endangerment or extinction. Of more concern is the primary gear with which this species is captured. Summer flounder are captured by bottom trawl. This method is known to cause significant damage to seafloor habitat and known to capture an incredible amount of non-target species. Without continuing advances in the way summer flounder are targeted, the systems in which this flounder live will continue to be affected by destructive fishing.

 

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Additional Resources:

IUCN Red List

NOAA Fisheries

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