American plaice fish identification, Habitats, Fishing methods, Canadian plaice fish characteristics
American plaice is a sedentary, slow-growing flatfish ranging from southern Labrador to Rhode Island, generally distributed in deep water from 90 to 180 m, and do not occur in waters less than 25-35 m. They have a large mouth and the characteristic eyes on one right side of its body. Like its relatives, it lives sideways flush with the ocean floor. It has a rounded rather than a forked tail, which helps distinguish it from the immature Atlantic halibut. American plaice spawn in the Gulf of Maine, with peak activity in April and May. They grow to a maximum length of 80 cm (32 inches).
The American plaice or sole, Hippoglossoides platessoides, also known as Sea Dab, Canadian plaice, Sand Dab, Black Dab,
Ложный Палтус or
Зубатая Камбала in Russian, is a right eyed flounders that belongs to the family Pleuronectidae. American plaice are an Atlantic species that ranges from southern Labrador to Rhode Island. In the eastern Atlantic, they occur from eastern Greenland and from the English Channel to the coast of Murmansk on the Barents Sea in northern Europe. In the western Atlantic, they range from southern Labrador and western Greenland to Rhode Island and from Newfoundland to Cape Cod, and the coasts of England and Scandinavia.
Scales ctenoid with free edges on the entire ocular side, small ctenoid or cycloid on blind side, smooth-edged except on the rear part of the body and along the bases of the fins; 85 to 97 scales in lateral line, 26 to 44 between lateral line and middle of back. Lateral line is nearly straight from end to end, except for a slight arch over the pectoral fin just behind the gill openings. The dorsal fin originates in front of the middle of the left eye and the anal fin arises slightly in advance of the base of the pectoral fins. Both fins are long and taper toward the head and the tail. There is a short, sharp, strong pre-anal spine (the continuation of the post abdominal bone) pointing forward close in front of the anal fin. Contours of posterior parts of dorsal and anal fins (at least in adults) are more or less convex. The pectoral fin on the eyed side usually (not always) has 1 or 2 more rays than its equal fin on the blind side, and is longer and more rounded, but the 2 ventral fins, which are close in front of the anal fin though entirely distinct from it, are alike in size, shape, and location; pectoral not quite 1/2 length of head. The margin of the caudal fin is always convex, double-truncate, either rounded or with its middle rays so much the longest as to form a blunt angle; caudal peduncle as long as deep or a little deeper than long. Fins are with small, rough scales.
Body ovate or rather elongate, strongly compressed, moderately wide (really deep), its depth is 2/5th of a length, more rounded in outline than the halibut. Head is 1/4th of a body length. Eyes on the right side separated by an obtuse narrow interorbital space, with a raised obtuse ridge entirely covered with rough scales in about 6 series, the upper close to edge of head, but without vertical range. Eyes are rather large; the upper is longer than snout, 1/5th in head. Pointed snout is as long as or shorter than eye; anterior margins of eyes about level. Mouth rather large, oblique, wide open; maxillary narrow, extends at least below the middle of the eye, at least 1/3rd in length of head; one irregular row of sharp, small, conical teeth in each jaw; lower jaw with a little projecting knob at the chin, teeth in the lower are the largest; anterior teeth of upper jaw not greatly enlarged, not forming distinct canines. Gill rakers are rather short and robust, not toothed, about 10 below angle, the longest less than 1/2 length of eye.
American plaice run more consistent in color than most of smaller flatfish of the family, ranging from reddish to greyish brown (darker or paler) above and pure or bluish white below. The tips of the rays of the two long (dorsal and anal) fins are white. Occasionally the right edge of the eyed side could be white (like the blind side) from the gill opening to the rearmost ray of the ventral fin but this is unusual. Small fish are usually marked with 3 to 5 dark spots along each edge of the body; large ones are occasionally, though they are plain colored as a rule.
The eyes are on the right side of the body. Slender body, about 2.5 times as long to base of caudal fin as it is wide. Very large mouth. The tail fin is rounded. The dorsal fin starts above left eye. Lateral line is almost straight. Rough small scales.
76-101 (78-98) Dorsal soft rays
60–79 Anal soft rays
9-12 Pectoral soft rays on eyed side
18–19 Caudal fin rays (12 or 13 branched)
85-97 Scales on lateral line
9-12 Gill rakers on lower part of anterior arch
Max length: 32 in (80cm)
Max weight: 14 lbs
American plaice is right-handed and large-mouthed like the halibut and it is easily distinguished from halibut by its rounded tail instead of concave and with the lateral line nearly straight instead of arched. It is the only Gulf of Maine flounder in which these characters are combined.
Other large-mouthed flat-fishes with rounded tails are sand flounder,
Summer Flounder and four-spotted flounder, are left-handed, and the wide-gaping jaws readily distinguish the American plaice from the various small-mouthed flounders.
American plaice are bottom fish. Like some other flatfishes, they avoid rocky or hard bottom, preferring a soft bottoms, fine, sticky but gritty mixture of sand and mud, such as floors much of the Gulf between the hard patches, from the 36 m to the 180 m deep. While American plaice are a cold water (an arctic-boreal) species, they however appear to have a fairly wide temperature tolerance. It occurs in temperatures ranging from about -1.5°C to above 5°C and from inshore localities down to 700 m. However, the preferred temperature for this species appears to be in the range from just below 0°C to about 1.5°C and principally in the 90 to 250 m depth range. As a rule, plaice encountered in the deeper ranges are at higher temperatures. Although the normal habitat is at or near the ocean floor, plaice frequently move off the bottom, usually at night, possibly in pursuit of prey species such as capelin.
Larval plaice feed on minute plants and animals that are present in the upper water layers. When they settle to the floor of the ocean their diet gradually changes as the fish grow and the mouth size increases and accommodates a wider variety of prey. Adult plaice feed on such things as sand dollars, brittle stars, shrimp-like animals, marine worms called polychaetes, crustaceans of various kinds, molluscs, and fish; primarily capelin and launce. As a matter of fact, the latter make up most of the diet of plaice in some localities.
American plaice became mature between ages 2 and 3, most individuals do not reach sexual maturity until age 4, but in the far north they became mature after 7 to 10 years. Spawning occurs in spring, between January and June, generally during March through May, as early as the first part of April on the Flemish Cap, and on the southern half of the Grand Banks, to late May or early June off Labrador.
American plaice Individual females produce 30,000 to 60,000 eggs, according to size. The eggs are buoyant and have no oil globule, but they have a transparent (perivitelline) space around the yolk so broad that they are not likely to be confused with those of any other Gulf of Maine fish. This space is formed by the entrance of water between the egg proper and its covering membrane, after the eggs are shed and it about doubles the total diameter of the egg. The eggs have averaged about 2.5 mm. in diameter, but could be as small as 1.38 and as large as 3.2 mm. in different areas, depending on the breadth of the perivitelline space.
The length of time between fertilization and hatching of the eggs varies considerably depending on the water temperature in the upper layers. Hence, developing eggs and larvae being pelagic until the latter reach a length of 2-3 cm, when they live in mid-water; they could drift a considerable distance before the young fish finally settle to the bottom. Incubation occupies 11 to 14 days at a temperature of 39° F.
During the development of the egg, minute black and yellow pigment cells are scattered over the embryo, not aggregated into any diagnostic clusters. But the pigment gathers in five definite groups very soon after hatching (which takes place when the larvae are 4 to 6 mm. long); one on the gastric region, one about the vent, and three behind the vent; a pattern similar to that of the larval witch flounder. The only other flatfish species for which the larval American plaice are similar and could be mistaken are the witch flounder and the halibut; but the witch is longer at corresponding stages of development, but with the distance from snout to vent proportionately much shorter, and the outlines of throat and abdomen are sufficiently different to distinguish the dab from the halibut.
The yolk is absorbed about 5 days after hatching, when the larva has grown to 6.2 to 7.5 mm. in length. The caudal rays appear shortly after this, the dorsal and anal rays at about 11 to 12 mm. and the 3 vertical fins are differentiated at about 15 to 18 mm. By this stage the body has begun to assume the deep but very thin form characteristic of all young flounders, while the jaws have developed sufficiently to show that the little fish belongs to one of the large-mouthed species. The left eye may commence its migration when the larva is about 20 mm. long, while Welsh found it visible above the outline of the snout in Gulf of Maine specimens of 24 mm. and almost at the dorsal edge at 34 mm. But larvae as long as 35 mm. may still be symmetrical in other seas.
American plaice are strongly compressed laterally and lie and swim on one side. When the young fish hatch from the egg, at or near the surface, they have the normal fish form. During development, as they settle to the bottom of the ocean, a change occurs in the body structure. The head becomes twisted so that the fish now swims and lies on its side. The upper side (which now has both eyes) is normally pigmented as compared to the lower side which lacks pigmentation. Plaice almost invariably have their eyes on the right side of the body.
Growth is rather slow; by their first winter the little fish grow to a length of 2 to 3 inches; their exact size is depending upon how early in the season they are hatched, and on the temperature in which they live. 1 year old fish average about 3 inches long, when they are 3 year old fish are normally between 22 and 28 cm (9 to 11 in.) in length, and weigh between 90 and 190 g (0.2 to 0.4 lb). After age 4, females grow faster than males. The American plaice can grow to 32 inches and 14 pounds; it lives for some 17-20 years (females).
American plaice come from marine fisheries. They are primarily caught with bottom trawls. Additional types of fishing gear include gillnets, seines and hooks-and-lines. Once cooked, the meat is pure white, lean, boneless and flaky with a mild flavor. Its meat is white and tasteful and very delicate, it is therefore better to cook it over medium heat and not too long. American plaice is sold fresh and frozen as whole fish, fillets and blocks as well as fully prepared in various value-added presentations.