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Atlantic halibut fish identification, Habitats, Fishing methods, fish characteristics
The Atlantic halibut are demersal fish, that live on or near sand, gravel or clay bottoms at depths of between 160 and 6,600 ft (50 and 2,000 m). The halibut is the largest species of flatfish found in the northwest Atlantic Ocean and is among the largest teleost (bony) fish in the world, reaching lengths of up to 15 ft (4.7 m) and weights of 710 lb (320 kg). Halibut are strong swimmers and are able to migrate long distances. Halibut size is not age-specific, but rather tends to follow a cycle related to halibut (and therefore food) abundance. This long-lived, late-maturing flatfish is distributed from Labrador to southern New England.
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The Atlantic halibut, Hippoglossus hippoglossus, is a flatfish of the
family Pleuronectidae, native to the Eastern Atlantic from Bay of Biscay, Gulf of Cadiz to Spitsbergen, Barents Sea, Iceland, eastern Greenland, Irish Sea and English Channel, around Northern Ireland and Scotland and in the northern part of the North Sea. In Western Atlantic they range from southwestern Greenland and Labrador in Canada to Virginia in USA, including New Jersey, New York, off Block Island and Nova Scotian Banks.
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Description:
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The Atlantic halibut is a right-eyed flounder with comparatively elongate, not strongly compressed body, and deep medially, thence rapidly narrowing each way, about 1/3rd as wide as it is long. It has broad head with wide, oblique mouth, the maxillary reaching middle of the eyes. Mouth is armed with sharp curved teeth. Teeth in the upper jaw in 2 series, those below in 1; anterior teeth in upper j aw, and lateral teeth in lower, strong; no teeth on vomer or palatines; lower pharyngeal teeth in 2 rows. Eyes large, separated by a very broad flattish area; lower eye slightly advanced.
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The dorsal fin beginning above the eye and runs back the whole length of the fish, elevated but slightly for the first third of its length and then suddenly, to narrow again toward the caudal peduncle. The anal fin is similar to the dorsal fin in shape but is shorter, originates close behind the pectorals, and is preceded by a sharp spinelike extension of the post-abdominal bone, which projects in young fish but is hidden by the skin in old fish. The two pectoral fins are of different shapes, the one on the eyed side being obliquely pointed while the fin on the lower side is rounded. The end of the caudal fin is concave. The rather small ventral fins, which are situated in front of the pectorals and are separated from the anal by a considerable space, are alike. Halibut, like other flatfishes are scaly on the whole head and body and they are very slimy with mucus. Scales are very small, cycloid; lateral line with a strong curve in front. Gill rakers few, short, compressed, wide set.
Key characters
This is the largest of flatfishes. It lies on the left side; mouth gapes back as far as the eyes, and is armed with sharp curved teeth; the rear edge of its tail fin is concave, not rounded; 2 ventral fins are alike; lateral line is arched abreast of the pectoral fin. Also it is a narrower fish, relatively, than most of our flatfishes (only about one-third as wide as it is long) but is very thick through, and its eyes are farther apart than they are in most of the other flounders.
98-110 dorsal soft rays
73–85 anal soft rays
150 scales on lateral line
16 + 34 Vertebrae
Max length: 4.7 m male; 3 m female
Max. Weight: 320.0 kg
Max. Age: 50 years
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The halibut eyed side is a uniformly dark chocolate to olive or slate brown, and can be almost black. Young fish are lighter, and are more mottled, marbled or spotted with paler marks, while large ones are more uniform and darker. The blind side usually is pure white in small fish, but large ones are often more or less blotched or clouded below with gray. Occasionally a halibut blind side can be marked with patches of the same dark brown color as the eyed side. Halibut, like other flounders, must be nearly invisible as they lie on bottom, capturing any fish that passes within reach by a sudden rush.
Habitats:
The halibut, like all the flatfish tribe, is usually a ground fish, but it comes to the surface on occasion. They are usually found on sand, gravel, or clay, not on soft mud or on rock bottom in depth 700-900 meters in water temperature ranging from 32°-56° F (-0.5 to 13.6°C).
The young halibut drift weakly with the current for several months after hatching in the mid-depths. During this period they tend both to rise in the water as they grow, and to be carried inshore, so that when they finally take to the bottom they do so in quite shallow water. But the fry as a whole tend to work offshore again thereafter, and deeper.
The diet of the halibut depends mainly on what other ground fish are most easily available and it changes with increasing size. Fish up to 30 cm in length feed almost exclusively on invertebrates, mainly annelids and crustaceans (crabs, shrimps); those 30-80 cm in length feed on both invertebrates (mainly crustaceans, some mollusks) and fish; and those greater than 80 cm in length are benthic but occasionally pelagic. Feed mainly on other fishes including cod, haddock, pogge, sand-eels, herring, capelin, cusk, rosefish, grenadiers, silver hake and sculpins). They preying on flounders of various sorts (these seem to be their main dependence), skates, wolffish, and mackerel, but also takes cephalopods, invertebrates like lobsters, crabs, large shrimps (Pandalus borealis), clams, and mussels and other large crustaceans and other bottom-living animals.
Spawning:
Atlantic halibut reach sexual maturity between 5 to 15 years and the female age of maturity is about 7 to 9 years, males mature when they are somewhat younger. Females are batch spawners, able to ovulate several batches of eggs in a single reproductive season. They spawn once per year in synchronous groups during late winter through early spring. In the eastern Atlantic halibut spawn from January to June, but primarily in March, April, and May with the pick in April. Off west Greenland they spawn late in spring. Off the American coast the spawning season continues through the summer, in April, May, June, July, August, and early September. Spawning is occur in waters of the upper continental slope on bottom, like other flat-fishes, at depths of 700-900 meters or even greater than 1000 meters while the Pacific halibut is known to spawn at depths of 270 – 400 meters.
Females can produce up to 7 million eggs per year depending on size on harder substrates of sand, gravel, and clay. Large female of about 200 pounds is containing 2,2 millions eggs, while a female of the Pacific form of 140 pounds may have as many as 2,7 millions. The halibut egg is among the largest of planktonic fish eggs diameter of 3-4 mm. The eggs are buoyant, drifting suspended in the water at depths from 50 to 200 m, not at the surface. Usually they do not have any oil globule. The buoyant eggs of the Greenland halibut are larger. Eggs hatching approximately in 13-20 days at a temperature of about 43°F (6°C.).
The larvae were 6.5 to 7 mm. long at hatching, with very large yolk sac and no pigment, growing to about 8.5 mm. by the sixth day, and developing pigment by the 10th day. 13.5 mm. long hatched Atlantic halibut has vertical fin rays appearing. The dorsal and anal fins are developed and the ventral fins are visible at about 22 mm, by which time the left eye has moved upward until its margin is just visible above the contour of the head, forecasting that the fish is to be a right-handed flatfish. Fish of this size also show the large mouth characteristic of the species. Up to this stage there is little pigment. About one-fourth of the eye appears above the profile when the little halibut is about 27 mm. long, but even at 34 mm. the eye has not entirely completed its migration, though the pigmentation is stronger on the right side than on the left, and the caudal fin (previously rounded) has become square tipped. The younger larvae (up to about 25 mm. in length) are made recognizable as halibut by their curiously upturned snout. Fry of 3 to 6 inches (80-150 mm.) probably are in their second year. Juveniles start to emigrate from nursery areas when the fish are 3-4 years old.
Fishing Methods:
The halibut, like all the flatfish tribe, is normally a ground fish. But it comes to the surface on occasion, and it is a very powerful fish, when hooked. Halibut caught in shallow water are very active, usually starting off at great speed when they are hauled up from the bottom, often spinning the dory around in their attempts to escape. They are usually found on sand, gravel, or clay, not on soft mud or on rock bottom. They are utilized fresh, dried or salted, smoked and frozen; can be steamed, fried, broiled, boiled, microwaved and baked. Atlantic Halibut is a very sporting fish as well as very delicatessen and welcome on the table.
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