Animalia Life

Pseudopleuronectes americanus
FAMILY
Pleuronectidae
TAXONOMY
Pleuronectes americanus Walbaum, 1792, New York. Solea solea Pleuronectes platessa
OTHER COMMON NAMES
English: Blackback, Georges Bank flounder, lemon sole, rough flounder; French: Limande-plie rouge; Spanish: Solla roja.
PHYSICAL CHARACTERISTICS
Medium-sized, dextral flatfish with an oval and thick body with a relatively wide caudal peduncle and a broadly rounded caudal fin. The head is relatively small, with a small terminal mouth with a small gape and thick, fleshy lips. Jaws on the blind side are equipped with a series of incisor-like teeth, whereas the jaws on the ocular side are toothless or nearly so. The lateral line is nearly straight, with only a slight arch above the pectoral fin. Ocular side scales are ctenoid, whereas blind side scales are ctenoid in males and cycloid in juveniles and females. Winter flounder vary in color, depending on the bottom where they live. Larger specimens are dark muddy brown or reddish brown, olive-green, or slate-colored to almost black. On the ocular side, coloration varies from uniformly pigmented to patterned with definite flecks, spots, and darker blotches of differing hues, depending on the bottom type. The blind side usually is uniformly white and translucent with a bluish tinge toward the body margins and sometimes with yellow on the caudal peduncle. Winter flounder can attain a length of 24.8–26.4 in (63–67 cm) and weights to about 7.9 lb (3.6 kg). Winter flounder are relatively long lived, reaching a maximum age of about 15 years. After about age five, females begin to grow faster than males; they also live longer than males.
DISTRIBUTION
Western North Atlantic in estuarine and marine waters along the Atlantic coast of North America from Labrador south to Georgia and also on the offshore banks. Most abundant between the Gulf of Saint Lawrence and Chesapeake Bay.
HABITAT
Brackish waters of tidal rivers, estuaries, and river mouths to areas on the inner continental shelf. Larger and older fish tend to inhabit deeper waters than do younger, smaller fish. Typical inshore habitats consist of muddy sand, especially where the sand is broken by patches of eelgrass; clean sand; clay; and pebbly and gravelly ground. Offshore, winter flounder usually are found on hard bottom. They can survive a wide range of temperatures, from nearly the freezing point of saltwater to about 68–69.8°F (20–21°C). Their blood serum contains an antifreeze protein that helps protect them against freezing.
BEHAVIOR
Diurnally active, with activity beginning at sunrise. At night they lie flat, with heads resting on the bottom and eye turrets retracted. On muddy bottoms, winter flounder usually lie buried, all but the eyes, working themselves down into the mud soon after settling on the bottom. Fish living on tidal flats typically remain motionless during low tides but actively forage during high tides. Can change color to match background surroundings, ranging from whitish on white backgrounds to dark brown or nearly black on dark sediments. Local conditions in inshore waters appear to determine inshore
DISTRIBUTION
patterns, whereas offshore movements seem to be associated with extreme summer and winter conditions. In general, in summer months adult winter flounder stay in the shallow shore zone when the water temperature is not excessive and food availability is adequate. If these conditions are not met, they may move into deeper channels or offshore or may take evasive action. During winter in the southern parts of their range, they remain or move into shallow water to spawn, whereas in northern regions they remain inshore in protected areas and move offshore in exposed areas to avoid turbulence and drifting pack ice. Winter flounder in deeper waters, such as Georges Bank, remain there year-round. Winter flounder bury in sediments when water temperatures are below 32°F (0°C) and ice crystals are present in the water. They are active at water temperatures up to 71.6°F (22°C), beyond which they become inactive. They are sensitive to low levels (3 ppm) of dissolved oxygen.
FEEDING ECOLOGY AND DIET
Visual predators. Consume a wide variety of small invertebrates and, rarely, small fishes, such as sand lance. Principal food includes polychaetes, anthozoans, and amphipods but also shrimps, small crabs and other crustaceans, ascidians, holothurians, squids, bivalve and gastropod mollusks, and sometimes fish eggs. They often bite off clam siphons that protrude from the sand. While feeding, a winter flounder lies with its head raised off the bottom with its anterior body braced vertically against the bottom. Eye turrets are extended, and the eyes move independently of each other. After sighting its prey, the fish remains stationary, pointed toward the target, and then lunges forward and downward to seize its prey. Winter flounder are eaten by codfish, spiny dogfish, goosefish, hakes, winter skate, smooth dogfish, striped bass, bluefish, sea raven, seals, ospreys, gulls, blue herons, and cormorants.
REPRODUCTIVE BIOLOGY
In the fall, as gonads ripen, adult winter flounder remain in or move into shallow water to spawn. They spawn in winter in southern locations and in early spring (January to May) in more northern locations. Spawning in inshore waters occurs nearly at the seasonal lowest temperatures, which range from 31.1 to 35.6°F (_0.5–2.0°C), depending on latitude. Spawning on Georges Bank happens at temperatures ranging from about 37.9 to 41.9°F (3.3–5.5°C). Winter flounder spawn on sandy bottom and algal mats, often in shallow water. Spawning in estuaries occurs in areas with salinity levels as low as 11.4 ppt. Males mature at age two and females at age three off New York, when fish are 7.9–9.8 in (20–25 cm) in total length. Fish in more northern areas mature later—age three years and four months for males and three years and six months for females north of Cape Cod and age six for males and seven for females in Newfoundland. Maturity seems to be a function of size rather than age. On Georges Bank, the mean age at maturity is just under two years for both sexes. Females produce, on average, 500,000 eggs, but larger fish can produce up to 3.5 million eggs. Winter flounder migrate into shallow water or estuaries and coastal ponds to spawn, and tagging studies show that most return repeatedly to the same spawning grounds. They are batch spawners. Females in captivity spawned up to 40 times and males up to 147 times. Males initiated all observed spawning events, which occurred throughout the night but primarily between sunset and midnight. Spawning by one pair frequently elicited sudden convergence and spawning by secondary males. Strict pair spawning is uncommon. Male and female activity patterns were almost entirely nocturnal during the reproductive season but became increasingly diurnal during the post-spawning season. Eggs are fertilized outside the body and sink to the bottom, where they stick together in clusters. Incubation takes place over 15–18 days at 37–37.9°F (2.8–3.3°C). Young larvae hatch at about 0.12–0.14 in (3.0–3.5 mm). Metamorphosis is complete when larvae are only 0.31–0.35 in (8–9 mm) long. Winter flounder exhibit little movement from areas where they settle, unless seasonal temperatures become extreme.
CONSERVATION STATUS
Not threatened, although their numbers have diminished substantially since the 1970s, and the stocks throughout most, if not all, of the species’ range are considered to be overexploited. Overfishing, pollution, and habitats destruction all contribute to reductions in stock sizes of this species. Current fishery management plans are to restore stock sizes to former levels. As of 2002 little success was evident in these attempts.
SIGNIFICANCE TO HUMANS
Highly desirable commercial and recreational species. Winter flounder were the most frequently captured flatfish taken by recreational fishers along the eastern coast of the United States until about 1970. Since then, landings of fish in both commercial and recreational fisheries have declined substantially.

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