Southern Flounder fish identification, Habitats, Fishing methods, fish characteristics
The southern (or armless) flounders, also known as Flounder, mud flounder, doormat, and halibut are a small family of flounders found in Antarctic and sub-Antarctic waters. Paralichthys lethostigma is distributed in Atlantic coastal waters from North Carolina to Florida and in the Gulf of Mexico from Florida to Texas. This species is a common inhabitant of Alabama estuarine waters.
The southern flounder is a moderately large fish with oval, moderately elongate body, prominent eyes and a large mouth containing sharp, strong, canine-like teeth. Their bodies are greatly compressed, with both eyes on the left side of the head. Dorsal profile of head is slightly concave above eyes. Eyes are relatively small. The caudal fin is separate, and the pectoral fins are rudimentary or entirely absent; none of the fins have spines. Dorsal-fin origin is slightly anterior to vertical through anterior margin of upper eye. Maxilla is extending posteriorly beyond vertical through posterior margin of lower eye. Gill rakers are shorter than eye diameter. Scales are very small, cycloid. Ocular-side lateral line forms steep arch above pectoral fin.
Diagnostic characters include a rather large mouth with large sheathed teeth, an arch in the lateral line over the pectoral fin, and no ocellated spots on the pigmented side. The lateral line is straight and well-developed. Body depth 39 to 47% of length, Head length is 24 to 34% of length, upper jaw length is 47 to 51% of head length, extending posteriorly to a vertical through posterior margin of pupil on species length 35mm through posterior margin of eye on species between 35mm to 100mm in length, and beyond posterior margin of eye on species over 100mm in length. Eyes diameter is 15 to 19% of head length (desreasing with increasing species size); interorbital space flat and about as wide as eye diameter.
The eyed side is light olive brown to dark brown with or without diffuse pale and dark spots and blotches. It may also be whitish, bluish, and reddish to almost black. May or may not have ocellated spots. If spots are present, they may appear to merge into lines. Large species may be almost uniformly colored. Ocellated spots absent. The blind side is dusky or immaculate white. Spots tending to disappear in large individuals.
If there are pale spots present, they may appear to combine into lines. Upper jaw extends past rear edge of lower eye. Lateral line arched over pectoral fin. Body depth is about 36% of total length.
The eyes are on the left side
80 to 95 Dorsal fin rays
63 to 74 Anal Fin rays
11 to 13 Pectoral fin rays
85 to 100 Scales in lateral line
10 or 11 + 27 or 28 Vertebrae
Maximum Size 77 cm; common 60 cm
2 to 3 gill rakers on the upper limb of the first gill arch
8 to 11 gill rakers on the lower limb
Southern flounder have a special type of cell called a chromatophore in the skin on their pigmented side, which provides them with this adaptation. This cell contains a dark pigment (black and/or brown) called melanin. When the flounder is against a light bottom, the dark pigment is aggregated in one area of the cell, giving the fish a light coloration on the pigmented surface. When the pigment is dispersed through-out the cell, the fish’s color becomes dark. The southern flounder can also conceal itself by flexing its dorsal and anal fins to make a slight depression in the bottom causing the sediments to cover its back. This camouflage conceals the southern flounder and puts the fish in a position to strike prey as it passes overhead.
The southern flounder is often confused with the Summer Flounder or the Gulf Flounder, from which it can be differentiated by comparing counts of vertebrae, fin elements, gill rakers and body pigmentation. The large ocellated spots present on other species of flounder are much more diffuse in the southern flounder and generally disappear in adult individuals.
Visually, the Summer Flounder can be quickly separated from the summer and the Gulf Flounder by the lack of spots on the pigmented surface. The Gulf Flounder has three spots that form a triangle near the tail; the
Summer Flounder has five spots. In coastal South Carolina, the southern flounder is far more abundant, larger and caught in greater numbers by recreational anglers than the other two species.
This bottom dwelling predator found over soft sediments (mud, clay, silt) in estuaries and coastal waters to about 40 m, adults also entering rivers. They prefer muddy bottoms throughout most of the estuary, but it can occur in channel and bay mouths and also frequents areas around piers, pilings, and rock jetties. The southern flounder spends most of summer in brackish waters, moving to deeper marine waters for spawning in autumn and winter. They occur over wide temperature and salinity ranges, however temperatures below about 7°C in saltwater are considered fatal for adults; optimal temperature for maximum growth in estuaries is greater than 30°C. Juveniles are found in Atlantic estuaries when temperatures are as low as 2 to 4°C; juveniles begin to immigrate into bays when water temperatures are as low as 14°C, with peak immigration occurring when water temperatures average 16°C.
A voracious predator feeding chiefly on fishes, crabs and shrimps; juveniles take mainly small benthic invertebrates. This species is lying in total camouflage on the bottom until unsuspecting preys wander within reach and are capture with lightning quick movements. Foods of this species include shrimp and fishes.
Males grow slower than females and reach about half the size of females. Male southern flounders are mature when about 2 yrs old, between a length of 8 and 9 inches, 50% of the fish could spawn between 10 and 11 inches. All males are mature at a size of 13 inches total length. The female southern flounder are sexually mature at starting 12 inches total length and up. Half the females about 14 inches long were able to spawn. All fishes 16 inches and larger in length are mature.
Migrations to offshore spawning grounds begin in late fall at the onset of cold weather, and spawning is completed during winter months. Males begin to migrate offshore before females. Southern flounders spawn in offshore waters at depths of 20 to 60 m during late fall and early winter, September to April with a peak spawning from November to January.
The southern flounder can produces several clutches of eggs over the spawning season. The fish spawn the mature eggs and sperm producing a group of fertilized eggs that hatch into larvae, and after some rest produce another clutch of mature eggs. Larger females produce individual clutches with more eggs, have more clutches and spawn over a longer period of time than the small females. Single female produced from 17,000 to 260,000 eggs in a single batch.
The fertilized eggs are pelagic, that is, after the sperm and egg fuse and development begins, the eggs float to the surface. The eggs hatch in 48 hours when held at 70º F and the resulting larvae are a tenth of an inch long. The larvae are suspended in the water off the bottom and as they drift with ocean currents, the small southern flounder feed on very tiny animals related to crabs. In the larval stage, southern flounder swim like any other fish, and the eyes are located on opposite sides of the head. Also, they are largely translucent, which makes them less visible to potential predators.
The young are transported by ocean currents to estuaries along the coast, move inside the estuaries and settle out in the shallow tidal creeks. After moving from the shallow tidal creeks, the fish move to the larger parts of the estuary where most feeding and growth take place.
The diet of juveniles in the nursery area varies according to size. Those about 2 inches in length feed on mysid and grass shrimp, while those between 2.5 and 8 inches eat mainly small fishes such as juvenile spot, young striped mullet, grass shrimp and mummichogs (mud minnows). After growing and moving from the creeks to other areas of the estuaries, species change their diet both in the types of food eaten as well as the size of the individual food items. The diet of larger Southern Flounder consists mainly of these same fishes, which are consumed in a greater volume and larger size.
The southern flounder is a valuable sport and commercial fish along the gulf coast. Sport fishing is done by hook and line, bottom fishing, trolling natural baits, and by gigging. Gigging is accomplished at night on a high, clear tide using a three-pronged, long-handled spear and a strong light. Wading the periphery of saltmarshes, or poling the tidal creeks in a shallow-draft boat, the experienced fisherman can discern the outline of a buried flounder, cautiously approach it, and then plant his gig in the fish's head. This sport is interesting because the lantern illuminates multitudes of fishes, crabs, shrimps, and other marinelife. Another method used to catch southern flounder is to bump live minnows over the bottom of inlets and tidal creeks by slowly trolling against the current.
Southern flounder are marketed fresh and are considered excellent food fish, the flesh is white firm, and succulent. It is by far the most important flatfish of the Atlantic states. Prepare by broiling, baking, or frying. Baked flounder may be stuffed with crabmeat or scallop dressing.