Summer Flounder fish identification, Fluke Habitats, Fishing methods, fish characteristics
Summer Flounder, often called fluke, is the largest and most prized of the flounders. It has both eyes are on the left side and compressed, oblong body, commonly brown or gray with a white underbelly, and ranges from Nova Scotia to South Carolina. Summer flounder are able to blend into their background by adapting to the texture and color of the substrate. It undergoes a unique maturation from egg to adult flounder in which one eye migrates to the opposite side of the head. It reaches maximum length of 1.2 m, and the average-sized fish weighs 6.8 kg. It is harvested largely offshore. Harvest takes place year round with peak season between June and August. As the summer gets into full swing, Summer Flounder (Fluke) find their way into the harbors.
Summer flounder or Fluke, Paralichthys dentatus, is a member of the Bothidae family of flatfish, or left-eyed flounder, also known as American turbot, long-toothed flounder, common flounder, plaice, turbot, flatfish, chicken halibut, halibut, brail, puckermouth, plaicefish, lozhnyy paltus, zubataya kambala, live in estuaries and coastal waters from Gulf of Maine and occasionally Nova Scotia to Southern Florida, with greatest abundance between Cape Cod, Massachusetts and Cape Hatteras, North Carolina, most common between Cape Cod and Chesapeake Bay.
The summer flounder is a left handed flatfish because its eyes are on the upper surface of the head when the fish is facing left, and its abdomen is on its left edge as it rests on the bottom. The body is wide and flattened, rimmed by long dorsal and anal fins. The summer flounder is one of our narrower flounders. Its dorsal fin originates opposite the forward margin of the eye; its margin of its caudal is rounded, and its pectoral fins and ventral fins are smaller than those of the dab, relatively.
Body depth approximately 41 to 47% of length; Head length is 24 to 33% of the length. The eyes are close together on the left side of the body. Eye diameter is 15 to 20% of head length. Its mouth is large and well equipped with the teeth. The teeth are well developed on the right side of the jaw. Upper jaw length is 45 to 53% of head length, extending posteriorly through posterior margin of pupil on species 12.5 cm. in length, and beyond posterior margin of eye on species exceeding 30cm in length.
If there are 5 ocellated spots present, they are symmetrically set on posterior body: 2 on upper side below dorsal profile, 3-rd on lateral line, 4-th and 5th on lower side over ventral profile. Upper jaw extends to rear edge of lower eye. Lateral line arched over pectoral fin.
The eyes are on the left side of the body.
80-96 (usually 85-94) Dorsal fin rays.
60-73 (usually 63-70) Anal fin rays.
12-13 Pectoral fin rays.
91-106 scales in lateral line.
56-76 (usually 62-70) Scales on strait part of lateral line
Maximum length 70 cm, max weight 4.4 kg.
3-7 (usually 5-6) gill rakers on the upper limb of the first arch.
13 -18 (usually 15-17) gill rakers on the lower limb.
Summer flounder are called the chameleons of the sea because of their ability to change color to match the bottom on which they are found. The summer flounder is one of the most variable in color of all our local species and the one which adapts its pattern the most closely to that of the ground on which it lies. It is white below and of some shade of brown, gray, or drab above, like most flatfishes. But it can assume a wide range of tints, from nearly white on white sand through various hues of gray, blue, green, orange, pink, and brown to almost black. Its upper surface is variegated with pale and dark, as a rule, with the pattern fine or coarse according to the bottom, and it may or may not be marked with 5 symmetrically arranged small eyespots of a darker tint of the general ground color on pigmented side of body (becoming obscure in larger specimens), with the first two on upper side below dorsal profile and last two on lower side above ventral profile arranged in 2 triangles with a common apex situated on the lateral line. Generally they are white below and darker above, but they can turn various shades of gray, blue, green/orange and almost black.
Their distinguishing characteristics are the different color patterns, number of gill rakers, anal fin rays, and lateral line scales. Summer flounder have the most eyespots, Gulf Flounder have several eyespots, and Southern Flounder lack conspicuous spots. The most distinguishing attribute is, their very large mouth extends below and beyond its eyes. Itís large mouth similar to the sand flounder, which is also left-handed; but its two ventral fins are alike and each of them is separated from the long anal fin by a considerable space, whereas the upper left-hand ventral fin of the sand flounder is continuous with the anal fin. The only Gulf of Maine flatfish, with which the summer flounder shares its left-handedness, large mouth, and symmetrical ventral fins, is its close relative, the four-spotted flounder, but the color pattern of the latter is distinctive and it has fewer fin rays.
One of the eyes in each of the flatfish species migrates over the top of the head as the larval fish matures. In the case of the fluke, the right eye moves to the left side - the upper side - of the fish. This upper side is heavily pigmented, allowing the fish to blend in when it is lying on the bottom. The right - or lower - side is white, making the fish difficult to see fro lower down when it is up in the water column.
Most summer flounder inhabit bays and inlets close to the ocean in the summer and move offshore to depths of 120 to 600 feet of water during the fall and winter. Usually in waters less than 37 m deep and occasionally down to 183 m; but occurs at greater average depths to the south. Rarely enters waters of reduced salinities. Fluke spend most of their lives on bottom, or close to it, as other flatfishes do. During their stay in shoal water they prefer sandy bottom, or mud, where they are often seen. And it takes one only an instant to bury itself to the eyes in the sand. Fluke often lurk in eel grass or among the piling of docks; but they are swift swimmers when disturbed.
Summer flounder inhabit inshore areas during the warmer periods of the year. Fluke prefer eel grass beds and wharf pilings because of the protection they offer. In the summer, small and medium sized adults are found on the sandy and muddy bottoms of bays, harbors and along the open coastline. Most of the larger fish tend to stay in somewhat deeper water (50 to 60 feet). With the approach of fall, summer flounder migrate to more offshore waters in depths from 150 to more than 500 feet.
Like other flounders, this species is a bottom-dwelling predator, relying on its flattened shape and ability to change color and pattern on the upper (eyed) side of its body. A predator with quick movements and sharp teeth, the flounder is able to capture the small fishes, squid, sea worms, shrimp and other crustaceans that comprise the bulk of its diet.
The summer flounder, which depends upon sight to capture its food, feeds most actively during daylight hours. Larval and post larval flounder primarily feed on zooplankton (tiny floating animals) and small crustaceans. Juveniles feed upon small shrimp and other crustaceans, while adults are opportunistic feeders, eating whatever food is convenient at the time, and feed mostly on crustaceans and fish, including small winter flounder, menhaden, sand lance, red hake, silversides, bluefish, weakfish and mummichogs, as well as invertebrates such as blue crabs, squid, sand shrimp, opossum shrimp, small bivalve and gastropod mollusks, small crustaceans, marine worms, and sand dollars. Adults are very active predators, often chasing schools of small fish to the surface and leaping out of the water in pursuit of them. This behavior clearly distinguishes the summer flounder from other more sluggish species of inshore flatfish.
Both males and females become sexually mature at the age of 3. Summer flounder spawn during their offshore migration, from late summer to midwinter, starting as soon as the fish begin migrating to wintering grounds. Peak spawning activity occurs from early September through early November in water temperatures of 53 to 66 degrees F and at depths of 60 to 160 feet. The center of spawning activity occurs off the coasts of New York and New Jersey with less concentrated activity occurring in southern New England waters.
The fecundity (number of eggs produced in a single spawning season) of females increases with size and weight. A 14 inch female produces about 460,000 and a 27 inch female about 4,200,000 eggs in a season. Summer flounder have a high egg production to body weight ratio; in fact, the weight of annual egg production is approximately 40 to 59% of the weight of spawning females. Summer flounder are serial spawners - they release their eggs in several batches throughout the spawning season. The eggs float in the water column, hatching 3 to 4 days after being laid. The eggs of the summer flounder are pelagic (in the water column) and buoyant like those of the four-spotted flounder. Larval flounder have body symmetry and eyes on both sides of their heads.
Water currents carry larvae and post-larvae inshore into the estuaries and sounds, the Bay from October through May. Upon reaching the estuaries, larval flounder undergo a metamorphosis to the post-larval stage. During metamorphosis, the right eye of the larval flounder gradually migrates to the left side of the head, the feature distinguishing summer flounder from winter flounder, whose eyes are on the right side and the body takes on the flattened appearance that it retains as an adult fish. Once the metamorphosis is complete, the post-larval flounder at a length of 16 mm to 26 mm assumes the adults' bottom-dwelling lifestyle. Juvenile summer flounder often live among eelgrass beds in the bay.
Summer flounder are major recreational and commercial species. Anglers catch summer flounder from the shore, piers and boats with hook and line. Shoreline anglers use medium weight spinning gear length from 6 to 12 feet, spooled with 12 pound test monofilament line, while boat anglers fishing deeper water with strong currents need 15 to 20 pound test line on light to medium conventional gear to match the larger fish found there.
Fluke are well known for the aggressive way they grab bait and battle when hooked. They offer a particular challenge to the angler bold enough to use light tackle. Summer flounder can be found on sandy or muddy bottoms in many inshore habitats and are particularly abundant in fast moving rips that gather debris and bait fish. Anglers troll, chum, still-fish and cast for fluke, but the most popular method is drifting bait along the bottom. When drifting, the bail of the reel should be open and the line held by the finger. Once the line stops drifting and it tugged, it should run free for a moment to let the fish get the bait in its mouth before the hook is set. The best bait is live minnow, but casting baited red and white bucktail jigs juiced up with strips of fresh or frozen squid, sand lance, 4 to 5 inch strips of meat cut from the tails of fish such as sea robins or the belly area of a fluke or bluefish from boat or shore can also produce fish. The jig should be retrieved with a slow pumping action. When a fluke grabs the rig the rod tip should be lowered to slacken the line; when the line tightens again, the hook can be set.
Fish are likely to be holding on the channel edges, where a narrow area of deeper water surrounded by shallows, waiting for a free meal to wash by them. In the sand bars when the shallows are warmed quickly by the sun fish usually looking for food at the edges. In the Creek/River Mouths, areas with constant flows of bait washed out of the creeks into the waiting mouths of their predators.