Flounder are flatfish, recognized by their unique flattened bodies and remarkable ability to camouflage themselves. With both eyes typically migrated to one side of their head, they blend seamlessly with the seafloor, allowing them to lie flat and observe their environment.
Key Habitat Features
Flounder are demersal fish, meaning they live on or near the bottom of aquatic environments. They prefer soft substrates like sand, mud, or gravel. Their flattened bodies are an adaptation to this bottom-dwelling lifestyle, enabling them to rest inconspicuously on the seabed. Many species burrow partially into the sediment, enhancing their camouflage for ambushing prey and avoiding predators.
Diverse Living Environments
Flounder inhabit a wide range of aquatic environments globally, from shallow coastal areas to deeper offshore waters. Many species, particularly during their juvenile stages, utilize estuaries and coastal lagoons as nursery grounds, providing sheltered areas for growth, abundant food, and protection.
As they mature, flounder often migrate to deeper waters along the continental shelf, though some species remain closer to shore. For example, summer flounder are found in the Atlantic Ocean from Nova Scotia to Florida, commonly inhabiting waters from Massachusetts to North Carolina. Other species are found in the Pacific Ocean and around Europe, with some even residing in the Arctic. Certain flounder species are adapted to extreme depths, found in deep-sea regions, including trenches almost 7 miles below the surface. While most are marine, some tolerate brackish or even freshwater, particularly in lower coastal river areas.
Why Flounder Choose Their Homes
Flounder habitat selection is influenced by environmental factors like water temperature, salinity, and food availability. They migrate seasonally for optimal temperatures; for instance, summer flounder prefer 55°F to 72°F, moving to warmer, shallower waters in spring/summer and deeper, cooler waters offshore for spawning in fall/winter.
Salinity also plays a significant role in habitat distribution, particularly for different life stages. Larval and juvenile flounder exhibit specific salinity preferences, with some young southern flounder preferring low to medium salinity in coastal rivers and creeks, while small summer flounder favor higher salinity waters closer to inlets.
The presence of prey, such as crustaceans, small fish, and worms, is another determining factor, as flounder are ambush predators. These environmental cues guide their movements and ensure their survival and reproductive success.