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Atlantic Mackerel fish identification, its habitats, characteristics, fishing methods.
The Atlantic Mackerel is one the most common of the family Scombridae species usually find in huge shoals migrating towards the coast to feed on small fish and prawns during the summer. Atlantic mackerel are iridescent blue green above and silvery white underbelly with 20 to 30 black bars run across the top half of their body, giving them a distinctive appearance. Abundant in cold and temperate shelf areas, it forms large schools near the surface. They overwinter in deeper waters but move closer to shore in spring when water temperatures range between 11° and 14°C. The efficient spindle shape of their body and their strong tall fin give this fish its ability to move swiftly through the water. Atlantic Mackerel is extremely high in vitamin B12. It is also very high in omega 3 (a class of fatty acids), containing nearly twice as much per unit weight as does salmon. When raw, the meat looks grayish and oily, but when cooked, the meat is off-white to beige in color and soft, flaky, and moist in texture.
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The Atlantic mackerel (Scomber scombrus), also known as Mackerel, Tinker Mackerel, Northern Mackerel, Boston Mackerel, Common Mackerel, Caballa, Tinker, is a fast swimming, pelagic schooling species, found on both sides of the North Atlantic Ocean, including the Baltic Sea. They common from Norway to Spain off the European coast; from the northern side of the Gulf of St. Lawrence and Strait of Belle Isle to Cape Lookout, North Carolina off the American coast. In the eastern Atlantic, they range in the Mediterranean and the Black seas; in the western Atlantic, they range from Labrador to North Carolina. In north-east Atlantic: North Sea (east) and British Isles (west).
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Description
The mackerel is fusiform in outline, tapering rearward to a very slim caudal peduncle and forward to a pointed nose. Its body is about four and one-half to five and one-half times as long as it is deep, oval in section, thick and firm-muscled as are all its tribe. Its head is long (one-fourth of length to caudal) and its mouth large, gaping back to the middle of the eye (the premaxillaries are not protractile), while the jaws, which are of equal length, are armed with small, sharp, slender teeth. The eye is large, and the hollows in front of and behind it are filled with the so-called "adipose eyelid," a transparent, gelatinous mass in the form of two scales, a forward and a hinder, which cover the eye except for a perpendicular slit over the pupil.
Atlantic mackerel has two large dorsal fins: the first originating over the middle of the pectoral fins when the latter are laid back is triangular, of 8 to 14 (usually 11, 12, or 13) rather weak spines that can be laid down along the midline of the back in a deep groove; the second dorsal, separated from the first by an interspace longer than the length of the latter, is smaller (9 to 15 rays, usually 12) and is followed by several small finlets, of which there are usually 5, but sometimes 4 or 6. The anal fin is similar to the second dorsal in shape and size, originates slightly behind it, and is similarly succeeded by 5 small finlets that correspond to the dorsal finlets in size and shape.
The caudal fin is broad, but short and deeply forked. The caudal peduncle bears two small longitudinal keels on either side but no median lateral keel; the absence of the latter is being a distinctive character. The ventral fins stand below the origin of the first dorsal and are small, as are the pectorals. The scales of the mackerel are so small that its skin feels velvety to the touch; indeed they are hardly to be seen on the belly with the naked eye, but those about the pectoral fins and on the shoulders are somewhat larger.
Distinguishing characteristics: Atlantic mackerel are shining blue green above and silvery white underbelly with 20 to 30 wavy black markings on back oblique to near vertical, with relatively little undulating; a narrow dark streak that runs along each side from pectoral to tail fin below the bars; belly unmarked. Their body is spindle shaped, tapering at both ends. They have two separate large dorsal fins which are gray or dusky. The pectoral fins are black or dusky at the base, and the tail fin is gray or dusky. They have no well developed corselet; interpelvic process small and single; anal fin spine conspicuous, joined to the fin by a membrane but clearly independent of it; anal fin origin opposite that of second dorsal fin; no swim bladder; first haemal spine anterior to first interneural process; 21-28 interneural bones under first dorsal fin.
First fin: 8–14 dorsal spines, 113 soft rays
Second fin: 9–15 dorsal spines, 113 soft rays
Anal spine with 12-13 soft rays
Vertebrae: 31.
Max. Length: 22in / 55 cm
Max. Weigh: 7.5 lbs
Max. age: 20 years
The upper surface is dark steely to greenish blue, often almost blue-black on the head. The body is barred with 23 to 33 (usually 27 to 30) dark transverse bands that run down in an irregular wavy course nearly to the mid-level of the body, below which there is a narrow dark streak running along each side from pectoral to tail fin. The pectorals are black or dusky at the base; the dorsal and caudal fins are gray or dusky. The jaws and gill covers are silvery. The lower parts of the sides are white with silvery, coppery, or brassy reflections and iridescence; the belly silvery white. But the iridescent colors fade so rapidly after death that a dead fish gives little idea of the brilliance of a living one.
Habitats
The mackerel is a fish of the open sea; inhabit the inner half of the continental shelf with none straying beyond the shelf's outer edge. They are often encountered far out over the outer part of the shelf of the continent. The larger sizes tend to swim deeper than the smaller ones, on the whole, especially in mid and late summer. They can also be found as far down as 600 feet. The highest temperature in which mackerel are commonly seen is about 68° F (20° C.). At the opposite extreme they are sometimes found in abundance in water of 46°-47° F (8° C.) or even in winter in water as cold as 43°-45° F (6°-7° C.). The smaller species often enter estuaries and harbors in search of food, but never enter fresh water. But they are most numerous within the inner half of the continental shelf from spring through summer and well into the autumn, and their normal range seems not to extend ocean ward beyond the upper part of the continental slope, shoaler, mostly, than 150 to 180 ft, in which they difference with their relatives the tunas, the bonitos, and the albacores.
Mackerel are a swift-moving fish, swimming with very short sidewise movements of the rear part of the body and of the powerful caudal fin. They keep swimming constantly in order to bring sufficient flow of water to their gill filaments, to get much dissolved oxygen from the water for their vital processes. Despite their great activity, they do not leap, never "fin" or raise their noses above the surface, they make less compact ripple than that made either by herring or by menhaden. The mackerel has the habit of gathering in dense schools of many thousands by themselves, but sometimes they are found mingled with herring, alewives, or shad. Schools of mackerel are often seen at the surface, as deep as 48 to 60 ft by day, if the water is calm, and the sun behind him.
Atlantic mackerel are opportunistic feeders that can swallow prey in the spring and fall or by passive filter feeding in the summer which occurs when small plankton are abundant. Mackerel swim through patches with mouth slightly open, filtering food through their gill rakers.
Larvae feed primarily on zooplankton. First-feeding larvae (3.5 mm) are phytophagous, larger individuals (> 4.4 mm) fed on copepod nauplii, Acartia and Temora, larvae > 6.4 mm are cannibalistic, feeding on 3.5-4.5 mm conspecifics. With increasing larval length, the diet shifted from copepod nauplii to copepod and fish larvae; the fish larvae included yellowtail flounder, silver hake, redfish and a large proportion of conspecifics.
Juveniles eat mostly small crustaceans such as copepods, amphipods, mysid shrimp and decapod larvae. They also feed on small pelagic mollusks (Spiratella and Clione) when available. Adults feed on the same food as juveniles but diets also include a wider assortment of organisms and larger prey items, euphausiid, pandalid, crangonid shrimp, chaetognaths, larvaceans, pelagic polychaetes, amphipods (Euthemisto), annelid worms, appendicularians and larvae of many marine species including crabs and mollusks.
Larger mackerel prey for squids (Loligo) and fishes like silver and other hakes, sand lance, herring, and sculpinseven, on Aglantha digitale, a small transparent medusa. Immature mackerel begin feeding in the spring; older fish feed until gonadal development begins, actual ripening of their sexual products commences, stop feeding until spent and then resume prey consumption, when they commence feeding greedily. After spawning, the adult feed very actively moving around in small shoals.
Spawning:
Mackerel reaches reproductive maturity at age 2 and at lengths > 30 cm and usually complete by age 3. Spawning occurs near the surface during spring and early summer, when the water has warmed to about 46° F. (8° C.) with more northerly fish spawning later in the season as the surface waters warm and fish migrate. The pick of spawning is taking place when water temperatures from 48° to 57° F. There are two major spawning groups: a southern group that spawns primarily in the Mid-Atlantic Bight and Gulf of Maine from mid-April to June and a northern contingent that spawns in the southern Gulf of St. Lawrence from the end of May to mid-August. Small fish (< 30 cm) lag behind larger fish and spawn later. Most of the spawning occurs in the shoreward half of continental shelf waters, although there is some spawning on the shelf edge and beyond. Mackerel shed their eggs wherever their wandering habits have chanced to lead them when the sexual products ripen.
Atlantic mackerel are batch spawners, spawn between 5 and 7 batches of eggs per year, with estimates of total fecundity ranging from 285,000 to 1.98 million eggs for southern contingent mackerel between 12 and 17 in (31 and 44 cm) full length. The fecundity of females increases as a function of age and size.
Eggs and larvae are pelagic and spherical, ranging in size from 1.01-1.28 mm (avg. = 1.3 mm) in diameter, and have one oil globule ranging from 0.22-0.38 mm (avg. = 0.29 mm) in diameter. Eggs are generally float in the surface water, mainly shoaler than the 30m level, depths varies with season, egg diameter, thermocline and ranging from 10- 325 m, majority from 30- 70 m. Eggs hatch in 4 to 7.5 days, depending on water temperature, for example incubation takes about 6.25 days at 54° F and about 50 hours at 70°F with normal development limited to temperatures between about 52° and 70° F (11° - 21° C.).
Newly hatched larvae average 3.1-3.3 mm long with large yolk sac, and with numerous black pigment cells scattered over head, trunk, and oil globule which give them a characteristic appearance. It found between 5-10 m during the day, however, as they grow they’re at depths closer to the surface. Larvae (< 13 mm) occur primarily in offshore waters and in pen bays and estuaries. Most distributed at depths from 10-130 m, usually at < 50 m.
Hatching occurs 4-5 days at average temperature of 57° F (13.8°C). Yolk sac stage complete by 6th day at this temperature. The yolk is absorbed and the mouth formed, the teeth are visible, and the first traces of the caudal fin rays have formed by the time the larva is about 6 mm. long. The rays of the second dorsal and anal fins and of the ventrals appear at about 9-10 mm. post-larval stage, (to end of caudal fin); the first dorsal when the total length of the larva is about 14 to 15 mm. The dorsal and anal finlets are distinguishable as such in fry of 22 mm., and the tail fin has begun to assume its lunate shape, but the head and eyes still are much larger than in the adult, the nose blunter, and the teeth longer. In approximately two months at 50 mm. the little mackerel resemble their parents and reach 20 cm in December after about one year of growth.
Mackerel are most likely to be found anywhere along the shore, from deep water to shallow bays where a lot of food such as copepods or other small animal life in the water. The schools of young fish are likely stay nearer the coast. Even larger species sometimes come close inshore. Anglers fishing in harbors, also, troll or bait-fish for mackerel all along the coast are mainly catching the smaller sizes. In summers when young tinkers are plentiful inshore many of them are caught from the wharves in various harbors.
Most of the mackerel were caught formerly with hook and line, ground bait being thrown out to lure the fish close enough to the vessel. Anglers fish for them from boats or shoreline sites such as piers, jetties, bridges and beaches. They use medium or light action spinning rod rigged with 12-15 lbs test line with a single 1 oz mackerel jig or lure that resembles bait fish like sand eel or other, or with bait such as squid, small fish, and pork rind on long shank hooks with on line sinkers. They also take a bright artificial fly, and bite greedily on a white piece of clam, a piece of mackerel belly with skin, or on a sea worm, especially if attracted by ground bait. Mackerel strike hard and then momentarily release the bait before attempting to swallow it. Wait for the second strike and try to set the hook.
The mackerel is a delicious fish, but it does not keep so well as some other fishes that have less oil in their tissues.
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