Southern Flounder

The southern flounder (Paralichthys lethostigma) is a large left-eyed flatfish in the family Paralichthyidae native to the western Atlantic and Gulf of Mexico coasts of the southeastern United States. It closely resembles its northern relative, the summer flounder, but generally lacks the prominent pale-ringed spots found on that species, and the two have overlapping but distinct geographic ranges. Southern flounder occur from North Carolina south around Florida and along the Gulf Coast to Texas and northern Mexico. It is a popular sport fish throughout its range and is managed under state and regional fisheries programs, with some populations subject to stricter harvest regulations due to fishing pressure.

Southern flounder share the general Paralichthys body plan but have subtle differences from close relatives.

• Body: broad, oval, flattened, deep-bodied
• Eyes: both on the left side
• Coloration: mottled brown to gray-brown upper side, generally without the distinct pale ocellated spots seen in summer flounder
• Mouth: large, with prominent sharp teeth
• Size: typically 40-60 cm, among the larger Paralichthys species The absence of clear eyespot markings, combined with a more southern, Gulf-influenced range, helps distinguish it from the more northern summer flounder, though the two can be difficult to tell apart without close examination.

Southern flounder inhabit coastal and estuarine waters of the southeastern United States, ranging from North Carolina south through Florida and along the Gulf of Mexico coast to Texas and into northern Mexico. They favor soft sand and mud bottoms in bays, estuaries, and tidal creeks, often in relatively shallow, brackish-influenced waters, moving to slightly deeper nearshore Gulf or Atlantic waters as adults. Seasonal movements track water temperature, with fish moving into estuaries during warmer months and offshore to spawn in cooler months. Estuarine habitats serve as essential nursery areas for juveniles.

Southern flounder are ambush predators that lie camouflaged on the bottom of estuaries and coastal waters, striking at passing fish, shrimp, and other prey with quick lunges aided by a large, well-toothed mouth. They can also actively pursue prey over short distances. The species undertakes seasonal migrations, using estuaries and marshes as feeding and nursery grounds during warmer months before moving offshore to spawn in deeper Gulf or Atlantic waters during cooler months. Spawning occurs offshore, with pelagic eggs and larvae eventually drifting into estuaries where juveniles settle and grow. As opportunistic predators, they play an important role in structuring estuarine and coastal fish communities.