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Blue mackerel
Blue mackerel
Blue mackerel
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Blue mackerel
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Scombriformes
Family: Scombridae
Genus: Scomber
Species:
S. australasicus
Binomial name
Scomber australasicus
Cuvier, 1832
Synonyms

The blue mackerel (Scomber australasicus), also called Japanese mackerel, Pacific mackerel, slimy mackerel, or spotted chub mackerel, is a fish of the family Scombridae.[1][2]

Description

[edit]

The blue mackerel typically reaches 30 cm (12 in) in fork length. It can reach 44 cm (17 in) in fork length and 1.4 kg (3.1 lb) in weight.[3]

Mackerels have a round body that narrows into the tail after the second dorsal fin, similar to a tuna fish.[4] Blue mackerel are often mistaken for chub mackerel. In fact, blue mackerel were believed to be a subspecies of chub mackerel until the late 1980s. Though they are both in the same genus (Scomber), blue mackerel set themselves apart by differing structural genes than those of the chub mackerel.[1][5] Other, more obvious, characteristics set these two apart, like the longer anal spine of the blue mackerel, and the amount of spines on the first dorsal fin.[5]

Distribution and habitat

[edit]
Range of Scomber australasicus

The blue mackerel is found in tropical to subtropical waters of the Indian and Pacific Oceans.[1][3] In the Indo-West Pacific, there is a population in the Red Sea and western Arabian Sea, one in the Northwest Pacific (Japan, China, and Taiwan), and another one in the Southwest Pacific (Australia and New Zealand). Furthermore, the blue mackerel also occur in the eastern Pacific (Hawaii and Revillagigedo Islands, Mexico). It occurs in surface waters down to 300 m (980 ft).[1]

Biology and ecology

[edit]

The blue mackerel is known as a voracious and indiscriminate carnivore, devouring microscopic plankton, krill, anchovies, and dead cut bait, and striking readily on lures and other flies. When in a school and in a feeding frenzy, blue mackerel will strike at nonfood items such as cigarette butts and even bare hooks. They typically eat smaller pelagic fish. Due to their eating habits and their diurnal lifestyles, blue mackerel have evolved large eyes with higher sensitivity in their retinas.[6]

Lifespan

[edit]

In the East China Sea, blue mackerel spawn between February and May, when the water temperatures are ideal.[7] In New South Wales, most spawning occurs 10 km (6.2 mi) offshore in waters 100–125 m (328–410 ft) in depth. The East Australian Current can carry eggs and larvae away from the original spawning grounds, broadening the area in which blue mackerel are located. However, egg and larvae probability of surviving decreases the further they are carried by the current.[8] A mature blue mackerel is considered to be over 31 cm (12 in) long.[7] Mackerel can live up to 7 years and grow up to 50 cm (20 in) in length, but are most commonly found to be between 1 and 3 years of age.[9][10] Counting the marks on otoliths is used to determine the age of blue mackerel.[10]

Human interactions

[edit]
Blue mackerel caught off Java

The blue mackerel can be flighty and difficult to catch, especially in estuaries and harbors. Blue mackerel are caught for both commercial and private use, for food as well as bait for tuna and other fish.[11]

Blue mackerel are often used as cat food, but are also consumed by humans smoked, grilled, or broiled. While easy to fillet and skin, they are difficult to debone, and care must be taken to avoid damaging their soft flesh. Blue mackerel are also commonly used as meat binders. After being freeze-dried, the protein is extracted and put into other meat products to keep the meat and seasonings bound tightly together, allowing costs to be lowered and enhancing the flavor and texture of the product.[12]

Local names

[edit]

In Japanese, it is known as goma-saba[3][2] (胡麻鯖 sesame mackerel).

In New Zealand, it is known by its Māori name tawatawa which is a cognate to kawakawa, kavakava and tavatava which are the respective Hawaiian, Tongan and Samoan names for Euthynnus affinis.[13]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Blue mackerel

View on Grokipedia
from Grokipedia
The blue mackerel (Scomber australasicus) is a small, schooling belonging to the family , characterized by a body, two widely separated dorsal fins, and an iridescent greenish-blue coloration with dark zigzag bars on the back and spots on the sides. It reaches a maximum fork length of 44 cm and weight of 1.4 kg, with adults typically measuring around 30 cm. Native to tropical and temperate marine waters of the , it inhabits pelagic-neritic zones at depths of 87–200 m, often migrating oceanodromously and schooling by size alongside species like jack mackerels and sardines. Its diet consists primarily of planktonic copepods and crustaceans, supplemented by small fish and squids in adults. Also known as Japanese mackerel, slimy mackerel, or spotted , it supports commercial fisheries across its range, including and , where it is harvested for fresh, canned, and processed products, and is rated as Least Concern by the IUCN due to stable populations.

Taxonomy and description

Scientific classification

The blue mackerel is classified within the domain Eukarya, kingdom Animalia, phylum Chordata, class Actinopterygii, order Scombriformes, family Scombridae, genus Scomber, and species S. australasicus. Its binomial name is Scomber australasicus Cuvier, 1832. The genus name Scomber derives from the Greek skombros, meaning tunny or mackerel. The specific epithet australasicus is from Latin, referring to its distribution in southern regions of Asia and Oceania. Synonyms include Scomber antarcticus Castelnau, 1872; Scomber tapeinocephalus Bleeker, 1854; Pneumatophorus tapeinocephalus (Bleeker, 1854); and Pneumatophorus japonicus tapeinocephalus (Bleeker, 1854). Although historically confused with the (Scomber japonicus), S. australasicus is a distinct , differentiated via taxonomic keys based on meristic counts (e.g., spines) and body patterning.

Physical characteristics

The blue mackerel (Scomber australasicus), a member of the family , possesses a body that is streamlined, slightly compressed laterally, and tapers sharply to a narrow peduncle with two small keels on each side. The snout is pointed, and the body is covered in small scales with no well-developed corselet; a is present, and the interpelvic process is small and single. Coloration features an iridescent blue-green dorsum marked by narrow, oblique zigzag and undulating lines, transitioning to silvery sides and a pearly white ventral surface with thin, wavy broken lines. Fins are yellowish-green, with the first dorsal fin comprising 10–13 spines, the second dorsal fin having 11–12 soft rays followed by 5–6 finlets, and the anal fin consisting of 1 independent spine, 10–11 soft rays, and 5–6 finlets; the caudal fin is deeply forked with 17 rays, while the pectoral fins are large with 20–21 rays and the pelvic fins have 1 spine and 5 rays. The first anal-fin spine is stiff and strong. Adults typically reach a fork length of 30 cm, with a maximum of 44 cm and weight up to 1.4 kg. is evident in growth patterns, with females attaining slightly larger sizes than males; for instance, 50% maturity occurs at approximately 23.7 cm fork length in males and 28.7 cm in females off southern and eastern .

Distribution and habitat

Geographic range

The blue mackerel (Scomber australasicus) inhabits tropical and subtropical waters primarily across the Indo-West , with its core range spanning from the and eastward to ( southward), southward along all Australian coasts except the , and including . In the eastern Pacific, populations extend from eastward to , including records off . The species is also present in the eastern , as part of its broader distribution. The species exhibits seasonal migration patterns tied to warmer water movements, forming large surface schools. In eastern Australia, spawning occurs during winter and spring between southern and northern . These oceanodromous migrations facilitate its wide dispersal within oceanic currents. No evidence suggests significant human-mediated introductions like ballast water, though natural oceanic flows have supported its presence in peripheral areas such as . Population structure reveals some genetic differentiation, such as between populations in the and , and a distinct population in the ; however, populations off southeastern and around show little genetic difference despite overlapping ranges, influenced by schooling behavior that promotes localized persistence.

Environmental preferences

The blue mackerel (Scomber australasicus) inhabits marine environments ranging from coastal shelf waters to oceanic realms, primarily in the pelagic-neritic zone. It occupies depths from the surface down to 300 m, with typical occurrences between 50 and 200 m in areas. This prefers water temperatures between 10.8 and 24.3 °C, often aligning with warmer currents such as the , which influences its distribution and larval dispersal in subtropical and temperate regions. Blue mackerel thrives in saline marine conditions typical of oceanic and neritic habitats, while avoiding freshwater inflows or hypersaline extremes that could disrupt its pelagic lifestyle. It forms large, fast-moving schools in open water, often segregated by size and associating with baitfish aggregations like jack mackerels and Pacific sardines, enhancing its mobility across productive surface and midwater layers. As a strictly pelagic , blue mackerel does not associate with bottom substrates and is drawn to dynamic structures such as zones, where nutrient-rich waters boost productivity and support its habitat preferences.

Life history and ecology

Reproduction and spawning

Blue mackerel (Scomber australasicus) reach at approximately 31 cm in length, typically between 1 and 2 years of age. This size at maturity aligns with observations from populations in the western Pacific, where 50% maturity occurs around 29-32 cm fork length, varying slightly by year and region. Once mature, individuals exhibit batch spawning, releasing multiple clutches of eggs over the spawning period. Spawning occurs seasonally, with timing influenced by geographic location. In the , including northeastern waters, the season spans February to May, peaking in late winter to early summer as indicated by gonadosomatic index (GSI) data. Off the coast, spawning is more protracted, occurring year-round but with peaks in spring (September to November), particularly in late winter to early spring surveys off eastern . These events take place in offshore waters at depths of 100-125 m, where adults form dense schools for group spawning, a promiscuous without . Females produce 40,000 to 60,000 eggs per batch, with pelagic eggs that float in the . These eggs are transparent and spherical, measuring 1.05-1.30 mm in diameter, featuring a single oil globule for . Development proceeds through seven stages from fertilization to hatching, which occurs in 2-3 days under typical sea temperatures of 18-22°C. Hatched larvae are initially yolk-sac stages, growing rapidly in mid-shelf waters before settling into juvenile schools within a few weeks, transitioning to pelagic schooling .

Diet and feeding

The blue mackerel (Scomber australasicus) is a carnivorous with a diet primarily consisting of such as copepods and other small crustaceans, which form the bulk of its intake, particularly for smaller individuals. Adults supplement this with small , including anchovies (Engraulis spp.), and occasionally cephalopods like , as well as larval crustaceans, molluscs, fish eggs, and fish larvae. Blue mackerel employ a combination of filter feeding and active pursuit to capture prey, often in schooling formations where they ram through water columns to sieve planktonic organisms using specialized gill rakers that prevent escape of small particles. This ram-filtering strategy allows efficient consumption of copepods and krill, while larger prey like small fish are targeted through particulate feeding. Their voracious nature leads to opportunistic strikes on non-food items, such as lures or bait, especially during intense feeding events in schools. Feeding activity peaks during daylight hours, with higher rates observed at dawn and , and consumption intensifies in nutrient-rich, productive coastal waters where prey densities are elevated. As mid-level carnivores, blue mackerel occupy a of approximately 4.2, reflecting their position as predators of primary consumers like while serving as prey for higher trophic organisms. Ontogenetic shifts in diet occur as blue mackerel grow; juveniles primarily consume planktonic organisms, including copepods and other zooplankton, to support rapid early development, whereas adults transition to a greater proportion of small fish, krill, anchovies, and squids for higher energy needs. This dietary progression aligns with increasing body size and swimming capabilities, enabling access to larger, more mobile prey.

Growth, maturity, and lifespan

Blue mackerel (Scomber australasicus) display rapid early growth, with larvae increasing at approximately 1 mm per day until reaching 5 cm fork length (FL), followed by juveniles attaining 15 cm FL after 80 days and over 20 cm FL after 120 days post-hatching. By the end of the first year, individuals typically measure 20-25 cm FL, accelerating to 28-31 cm FL in the second year. Growth slows thereafter, with fish reaching 30-34 cm FL by age 2, 33-36 cm by age 3, and approximately 37 cm by age 4, approaching a maximum of around 45 cm FL. This pattern is modeled using the von Bertalanffy growth function, where parameters vary regionally; in southern Australia, asymptotic length (L∞) ranges from 385 mm for females to 453 mm for males, with growth coefficients (K) of 0.50 year-1 for females and 0.21 year-1 for males, while in New South Wales, L∞ is about 366-373 mm and K approximately 0.46-0.48 year-1 for both sexes. Sexual maturity is generally attained around age 2, though timelines differ slightly by and region. In southern Australian waters, 50% of males reach maturity at 236.5 mm FL (approximately age 1-2 years), while females achieve 50% maturity at 286.8 mm FL (around age 2). Northern populations mature at lengths exceeding 30 cm FL, with all individuals aged 2 and older considered mature. Age is primarily determined through analysis of otolith rings, which reveal annual growth increments. The lifespan of blue mackerel extends up to 7 years in Australian populations, though maximum ages of 11 years have been recorded in some studies. Most wild individuals, however, are aged 1-3 years due to high mortality from predation and anthropogenic factors like , with many reaching sizes under 30 cm FL before death. In waters, longevity estimates reach up to 24 years based on , though this may reflect less exploited stocks.

Human interactions

Fisheries and management

The blue mackerel (Scomber australasicus) supports commercial fisheries primarily through purse seine and midwater trawl operations, targeting its dense schools in epi- and meso-pelagic waters. Major fisheries operate in , particularly off in the eastern sub-area of the Small Pelagic Fishery (SPF), as well as in and New Zealand's Eastern Management Area (EMA) 1. In , annual catches have typically ranged from 6,000 to 15,000 tons during the 2020s, with a record of 6,202 tons harvested from the eastern stock in 2020/21. In New Zealand, catches have grown substantially since the 1980s, reaching over 10,000 tons combined for blue and jack mackerel in 2022/23, with blue mackerel at 7,961 tonnes in 2023/24, predominantly from purse seine vessels in EMA 1 north of 43°S. Japan's fishery contributes significantly to Pacific blue mackerel harvests, with most catches (around 80%) taken by coastal purse seiners, though specific annual totals for the species are integrated into broader mackerel quotas. The species' schooling aids efficient capture by these methods, minimizing search effort in targeted areas. Recreational harvesting of blue mackerel occurs via light tackle and is popular as live or cut for larger gamefish such as kingfish and . In , it ranks as a key recreational species off eastern coasts, with surveys estimating 114,000 individuals caught off in 2017–18 and 143,000 in 2019–20. In New Zealand, recreational take is lower and primarily for rather than direct consumption, though it remains accessible in areas like the . Fisheries management emphasizes stock assessments and precautionary quotas to sustain populations. In , the Australian Fisheries Management Authority (AFMA) conducts biennial assessments for SPF stocks, setting total allowable catches (TACs) such as 11,530 tons for eastern blue mackerel in 2023/24 and 15,510 tons in 2024/25 to avoid . New Zealand's Ministry for Primary Industries (MPI) performs annual plenaries and adjusts TACs for EMA regions, proposing increases like 763 tons for EMA 1 TACC in 2025/26 based on recent abundance data. has implemented a total allowable catch (TAC) system for blue and since 1997 under the North Pacific Fisheries Commission framework. Minimum size limits are generally absent in commercial operations across these regions, though recreational bag limits apply, such as 100 fish per person in and a combined 30 finfish daily limit in . Bycatch in blue mackerel fisheries remains low due to the selective nature of purse seining and midwater , which target schooling pelagics with minimal interaction with non-target . The South East small pelagic midwater trawl fishery, encompassing blue mackerel, holds (MSC) certification, valid through 2030, affirming sustainable practices. Blue mackerel holds economic value in fresh and frozen forms, supporting domestic markets and exports from Australian SPF operations primarily to Asian countries for processing and consumption. In , recent EMA 1 catch proposals are valued at around $372,000 annually based on 2023/24 prices.

Culinary uses and cultural significance

The blue mackerel (Scomber australasicus) is valued in culinary traditions for its oily flesh and robust flavor, which lend themselves to a variety of preparation methods. In , it is commonly cured using the sujime technique, involving salt and to preserve freshness, suppress odors, and firm the texture before serving raw as goma-saba in or . It is also grilled over coals in a dry-heat method to enhance its smoky notes, or pan-fried with and seasonings like sauce for a crispy exterior. Nutritionally, blue mackerel is a rich source of protein (approximately 21 g per 100 g) and omega-3 fatty acids (0.39 g per 100 g), supporting heart and brain health. Known locally as goma-saba (sesame mackerel) in Japan, tawatawa among Māori in New Zealand, and slimy mackerel or spotted chub mackerel in Australia, the fish's strong taste is balanced in dishes through marination or pairing with acidic elements like lemon or vinegar. Culturally, blue mackerel holds significance as a traditional food source for Māori communities in New Zealand, where it is harvested customarily as tawatawa for subsistence and sharing, reflecting broader Indigenous practices of sustainable marine resource use. In recreational fishing across Australia and New Zealand, it serves as bait for larger species like tuna. Additionally, its abundance supports processing into cat food, utilizing the whole fish for high-omega-3 pet nutrition. Available in fresh, frozen, or canned forms—such as simmered saba in miso—the blue mackerel's seasonal peaks in warmer months influence its prominence in coastal cuisines, where fresh catches are prioritized for grilling or raw preparations during abundance.

Conservation status

The blue mackerel (Scomber australasicus) is classified as Least Concern on the IUCN Red List, with the assessment conducted on 15 August 2022 and populations remaining stable as of 2025. Globally, blue mackerel populations exhibit stable trends, with key stocks classified as sustainable; for instance, the eastern Australian stock has an estimated spawning of approximately 88,000 tonnes based on 2019 surveys, and exploitation rates of around 15% remain below the sustainable limit of 23%. In the North Pacific, ongoing stock assessments by using virtual population analysis indicate no major declines, though separation from (S. japonicus) complicates precise monitoring. Primary threats include localized pressures, particularly in high-catch areas like eastern where commercial landings totaled approximately 5,900 tonnes in 2023–24, though current management prevents depletion. occurs in tuna purse-seine fisheries, but impacts are generally low due to the species' resilience and overlapping pelagic habitats. poses risks through warming waters that may shift ranges, as blue mackerel prefers warmer southern environments, potentially altering distribution in the . Conservation protections encompass inclusion in regional management frameworks, such as the North Pacific Fisheries Commission (NPFC), where member nations like implement total allowable catches and conduct assessments, though no species-specific conservation and management measure exists yet. In , harvest strategies under the Commonwealth Small Pelagic Fishery set total allowable catches (e.g., 11,440 tonnes for the eastern stock in 2021–22) alongside gear restrictions and spatial closures. The species is not listed under . Research gaps persist regarding long-term climate impacts on and distribution, as well as updates to genetic structure, with recent studies highlighting uncertainties in distinguishing populations . Monitoring involves annual ichthyoplankton surveys, such as the Daily Egg Production Method in , and acoustic-trawl methods in to track biomass and abundance.

References

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