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Narrow-Barred Spanish Mackerel fish identification, its habitats, characteristics, fishing methods.
The narrow-barred Spanish mackerel is an epipelagic species found throughout the coastal tropical waters of the Indo-Pacific from the Red Sea and South Africa to Southeast Asia, North to China, Japan, and south to both sides of Australia. One of the largest of mackerels, these fish can grow up to 2.2 meters, common to 90 cm in length and up to 70kg with more common weight of 10 to 15kg. They are vivid blue to dark grey in color along their backs and flanks that fades to a silvery blue grey on the belly. Spanish mackerel have scores of narrow, vertical lines down the sides.
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Narrow-barred Spanish mackerel, Scomberomorus commerson, is a mackerel of the Scombridae family, also known as Tinggiri. Spaniard. Tanguigue. Kingfish, King Mackerel, Konge Makrel and Kungs Makrill are widely distributed throughout the Indo-West Pacific from South Africa and the Red Sea east through the Indo-Australian Archipelago to Australia and Fiji and north to China and Japan. They are migrating to the eastern Mediterranean Sea by way of the Suez Canal. It is fished in numerous countries including Indonesia, India, Egypt, Madagascar and Pakistan.
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Description
Narrow-barred Spanish mackerel are the largest of all Australian mackerels growing to approximately 240cm and up to 70 kg. They have fusiform, elongated and compressed body. Two dorsal fins close to each other, caudal peduncle with a lateral keel between two smaller keels at the base of the tail. Maxilla (jaw hinge) is visible. First dorsal fin is highest in front, tapering to rear. Inter-pelvic process is small and bifid. Swim bladder is absent. Wavy lateral line abruptly bent downward in the caudal segment below end of second dorsal fin. They have very sharp teeth. Intestine has 2 folds and 3 limbs.
Distinguishing characteristics: The upper body varies from bright blue to dark grey in color that fades to a silvery-blue over the sides. More than 40-50 in adults, 20 in juvenile’s narrow grey-blue wavy, vertical bars are present on each side on the lower body. Bars are irregular, in part wavy and broken in spots, which is an exclusive characteristic. The large dip in the lateral line below the second dorsal fin is a clear diagnostic feature of the narrow-barred mackerel.
15-18 dorsal spines with 15-20 soft rays on first fin
15-20 dorsal soft rays, followed by 8 to 10 finlets on second fin
16-21 anal soft rays, usually 18-19 followed by 7-12 finlets
42-46 vertebrae (19-20 pre-caudal plus 23-27 caudal)
21-24 pectoral fin rays
1-8 gill rakers on first arch (0-2 on upper limb, 1-8 on lower limb).
Intestine with 2 folds and 3 limbs
Narrow-barred Spanish mackerel have sides silvery grey marked with transverse vertical bars of a darker grey; bars narrow and slightly wavy, extending from the flanks to the ventral surfaces, sometimes breaking up into spots ventrally; bars number 40 to 50 in adults but are usually fewer than 20 in juveniles up to 45 cm length; cheeks and lower jaw silvery white; first dorsal fin bright blue rapidly fading to blackish blue; pectoral fin light grey turning to blackish blue; caudal fin lobes, second dorsal, anal, and dorsal and anal finlets pale grayish white turning to dark grey. Juveniles differ from adults in that they have bars in a more dorsal position and the first dorsal fin with a black anterior segment followed by a white one.
Narrow-barred Spanish mackerel is similar in appearance to Wahoo. They have less dorsal fin spines (15-18 compared with 23-27), the second dorsal fin is located closer to the centre of the body and they have a more prominent fork in their tail.
Bars are irregular, in part wavy and broken in spots, which is an exclusive characteristic of this species (West African Spanish mackerel, Scomberomorus tritor has only spots, more or less round, on the flanks).
Habitats
This species is pelagic and oceanodromous. It is distributed along current lines from near the edge of the continental shelf to shallow coastal waters, often of low salinity and high turbidity. It is also found in continental shelf drop-offs, and shallow or gently sloping reef, islands and lagoon waters. It inhabits coastal waters at depths to 200 m, but is more frequently caught in areas less than 100 m depth. It usually hunts solitarily and often swims in shallow water along coastal slopes. It is known to undertake lengthy long-shore migrations, but permanent resident populations also seem to exist. It is found in small schools.
In winter and spring, adults aggregate to feed and spawn in coastal areas. At other times, fish probably disperse but remain in the same region. This dispersal may include some movement into deeper shelf waters.
Narrow-barred Spanish mackerel are voracious, carnivores, fast swimming, and opportunistic predators. They feed in the water column and mainly consume pelagic fish and cephalopods like anchovies such as Anchoviella and Stolephorus, clupeids such as Sardinella, small carangids, slipmouths (Leiognathus), also squid, and penaeid shrimps. Larger fish tend to eat larger prey items. Feeding apparently takes place day and night.
Spawning:
Narrow-barred Spanish mackerel spawn in oceanic conditions on reef edges. The fish often school by sex and by size during the spawning season. Spawning occurs in the late afternoon/early evening. Spawning times is associated with higher water temperatures that promote optimal food availability for the rapid growth and development of the larvae. Depending on temperature regime, the spawning season may be more or less extended. In east Africa they spawn from October to July, off Madagascar from December to February, in the coastal waters off Madras State from May to, off Taiwan Island in spring, off Papua New Guinea from July to December, on the Great Barrier Reef from October to December, and around Fiji from October to February with peaks in December and January.
Female became mature at about two years of age or at around 80 cm in length. The smallest mature males and females had fork lengths between 65 and 70 cm respectively. The oldest male was 10 years (127 cm, 19.0 kg), and the oldest female 14 years (155 cm, 35 kg). They are serial spawners and females are capable of producing a batch of eggs every 1-3 days during the spawning season. Fecundity is positively related to female body size, a 10 kg female has a batch fecundity of about 750,000 eggs.
Eggs have a large oil droplet that aids in buoyancy and keeps them at the top of the water column which is warmer, well oxygenated and has an abundant planktonic food supply for the larvae once they are hatched. Pelagic eggs and larvae spread along-shore drifting southwards with the Leeuwin current. Larvae probably remain in the plankton for less than 3 weeks. The larvae stay in their own species-specific groups and are not normally found with other mackerel larvae species of the same genus. This is not always the case with adult mackerel where occasional mixing of different species within the same genus can occur.
As the young larvae grow they move from the offshore spawning grounds to inshore and estuarine habitats where they are frequently found in the juvenile phase of their growth cycle. In the inshore environment they feed mostly on the larvae and juveniles of small fish and crustaceans until they become large enough to tackle small fish and squid.
Mackerel grow rapidly and are fully recruited to the fishery at age 2. Females grow faster and larger than males. Small mackerel (i.e. 1-5 years, <20 kg) tend to school and appear to be more mobile than larger fish. This species may live up to 22 years.
Narrow-barred Spanish mackerel are a highly valued fish throughout their range in the Indo West Pacific. They usually do long runs near surface, often followed by shorter runs in mid water. Recreational anglers catch mackerel from boats while trolling or drifting mullet, squid or strip baits often in combination with plastic squid and from boats, piers, jetties, and beaches by casting spoons and jigs and live-bait fishing. Commercial methods are primarily run-around gill netting, and rarely, by trolling lures similar to those used by recreational anglers. Slow deep trolling with bait or lures also work well as trolling lures, minnows and spoons, or drifting or at anchor with live bait and chum.
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