The Pacific jack mackerel (''Trachurus symmetricus''), also known as the Californian jack mackerel or simply jack mackerel, is an abundant

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

marine

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

in the jack family,

Carangidae The Carangidae are a family of ray-finned fish that includes the jacks, pompanos, jack mackerels, runners, trevallies, and scads. It is the largest of the six families included within the order Carangiformes. Some authorities classify it as the ...

. It is distributed along the western coast of

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

, ranging from

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

in the north to the

Gulf of California The Gulf of California (), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Vermejo''), is a marginal sea of the Pacific Ocean that separates the Baja California peninsula from ...

in the south, inhabiting both offshore and inshore environments. The Pacific jack mackerel is a moderately large fish, growing to a maximum recorded length of 81 cm, although commonly seen below 55 cm. It is very similar in appearance to other members of its genus, '' Trachurus'', especially '' T. murphyi'', which was once thought to be a

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

of ''T. symmetricus'', and inhabits waters further south. Pacific jack mackerel travel in large

schools A school is the educational institution (and, in the case of in-person learning, the building) designed to provide learning environments for the teaching of students, usually under the direction of teachers. Most countries have systems of ...

, ranging up to 600 miles offshore and to depths of 400 m, generally moving through the upper part of the

water column The (oceanic) water column is a concept used in oceanography to describe the physical (temperature, salinity, light penetration) and chemical ( pH, dissolved oxygen, nutrient salts) characteristics of seawater at different depths for a defined ...

Distribution and habitat

The Pacific jack mackerel is distributed through the northeastern

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

from

in the north, south to the western North American seaboard to the Baja California peninsula in the

. It has been reported as far south as the

Galápagos Islands The Galápagos Islands () are an archipelago of volcanic islands in the Eastern Pacific, located around the equator, west of the mainland of South America. They form the Galápagos Province of the Republic of Ecuador, with a population of sli ...

, but at these latitudes it would be sympatric with ''T. murphyi'', possibly resulting in confusion of the two species. Pacific jack mackerel occur in both

and inshore environments, often venturing up to 600 miles offshore and to known depths of 400 m. In more coastal environments, they are known to inhabit bays and very shallow waters.

Description

The Pacific jack mackerel is very similar to all other members of ''Trachurus'' and a number of other carangid genera, having an elongated, slightly compressed body with both the dorsal and ventral profiles of the body having the same degree of curvature. It is a medium-to-large-sized fish, growing to a maximum known length of 81 cm (32 in), although more commonly below 55 cm. The two separate

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

s are composed of eight spines and one spine followed by 31 to 35

soft rays Fish anatomy is the study of the form or morphology of fish. It can be contrasted with fish physiology, which is the study of how the component parts of fish function together in the living fish. In practice, fish anatomy and fish physiology co ...

, respectively. The

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

is composed of two spines

anteriorly Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Thi ...

detached followed by one spine connected to 26 to 30 soft rays. In some larger individuals, the last few rays at the posterior of the soft dorsal and anal fins are almost entirely separate from the rest of the fin, forming finlets. The

caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

is strongly forked, typical amongst Carangidae, while the ventral fin consists of one spine and five soft rays. The

pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

terminates before the front of the anal fin, having 22 to 24 rays in total. The

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelia ...

dips strongly after the pectoral fin, having 50 to 53

scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number ...

on the upper section and 43 to 52 keeled

scute A scute () or scutum (Latin: ''scutum''; plural: ''scuta'' "Scutum (shield), shield") is a bony external plate or scale overlaid with horn, as on the shell of a turtle, the skin of crocodilians, and the feet of Bird anatomy#Scales, birds. The ter ...

s posteriorly. The species'

teeth A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

are minute, with a patch of teeth on the

tongue The tongue is a Muscle, muscular organ (anatomy), organ in the mouth of a typical tetrapod. It manipulates food for chewing and swallowing as part of the digestive system, digestive process, and is the primary organ of taste. The tongue's upper s ...

in a narrow club-shaped strip. There are 24

vertebrae Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...

in total. Pacific jack mackerel are metallic blue to olive-green dorsally, becoming more silvery ventrally, before transitioning to a white belly. The top of the head and area near eye is quite dark with a dark spot on the upper rear of the gill cover. The fins are mostly

hyaline A hyaline substance is one with a glassy appearance. The word is derived from , and . Histopathology Hyaline cartilage is named after its glassy appearance on fresh gross pathology. On light microscopy of H&E stained slides, the extracellula ...

to dusky, although caudal fin may be yellow to reddish.

Relationship to humans

Pacific jack mackerel are fished commercially as well as for sport. They are often caught on baited hook from piers and boats, and also while salmon trolling. Commercial fishing occurs along the coast. Large individuals often move inshore and north in the summer. Pacific jack mackerel is canned in the same manner as salmon. Fish are cleaned, gutted and finned, then packed into cans with salt and water.

History

Before 1947, the pacific jack mackerel was of minor importance. It was referred to as the horse mackerel, and had little market appeal. However, in 1948, the

US Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

decided to allow the use of "jack mackerel" on all labeling, and that affected its appeal. The new label, combined with low catches of Pacific sardine in 1947-48 and increased catches of pacific jack mackerel during the same time, resulted in the fish gaining importance. In the past, mackerel consumption was considered a sign of low income. In the segregated

American South The Southern United States (sometimes Dixie, also referred to as the Southern States, the American South, the Southland, Dixieland, or simply the South) is census regions United States Census Bureau. It is between the Atlantic Ocean and the ...

, it was often associated with African Americans. Today, most of these stereotypes are gone.

As food

Pacific jack mackerel tastes similar to canned sardines. It may be used interchangeably with salmon or tuna in recipes. Jack mackerel is considered safer to consume than tuna because it is a smaller fish, and not a top predator, thus avoiding accumulation of heavy metals such as mercury.

Taxonomy and naming

The Pacific jack mackerel is classified within the

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

''Trachurus'', commonly known as the horse mackerels or jack mackerels. ''Trachurus'' is part of the jack family Carangidae, which is classified within the

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

Carangiformes Carangiformes is a large, diverse order of ray-finned fishes within the clade Percomorpha. It is part of a sister clade to the Ovalentaria, alongside its sister group, the Anabantaria (including Anabantiformes and Synbranchiformes). The Cara ...

. Recent genetic studies have divided the Carangidae into four

subfamilies In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zool ...

, with the genus ''Trachurus'' falling into Caranginae (or

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide use of the term in English is in the discipline of anthropology. The definition is contested, in part due to conflict ...

Carangini), being most closely related to the 'scads' of the genera '' Decapterus'' and '' Selar''. The species was first

scientifically described A species description is a formal scientific description of a newly encountered species, typically articulated through a scientific publication. Its purpose is to provide a clear description of a new species of organism and explain how it diffe ...

William Orville Ayres William Orville Ayres (September 11, 1817 – April 30, 1887) was an American physician and ichthyologist. Born in Connecticut, he studied to become a Physician, doctor at Yale University School of Medicine. Life and career Ayers, the son of J ...

in 1855 based on the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

specimen taken from

San Francisco Bay San Francisco Bay (Chochenyo language, Chochenyo: 'ommu) is a large tidal estuary in the United States, U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the cities of San Francisco, California, San ...

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

. He named the species '' Caranx symmetricus'', correctly identifying its relationship to the jacks, but incorporating it into what was later found to be the wrong genus. The fish was redescribed in 1944 under a different name, '' Decapterus polyaspis'', from a specimen caught in

Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...

, which under the ICZN rules classifies as a

junior synonym In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...

, and it is therefore discarded. In 1983, ''C. symmetricus'' was transferred to ''Trachurus symmetricus'' by William N. Eschmeyer and Earl Herald. The species has twice been treated as a

; once as ''Trachurus picturatus symmetricus'' (a subspecies of the blue jack mackerel), and the second more commonly used subspecies of ''Trachurus symmetricus symmetricus''. For many years, the latter was accepted as a valid combination, with ''Trachurus symmetricus murphyi'' considered to be a southern subspecies

population Population is a set of humans or other organisms in a given region or area. Governments conduct a census to quantify the resident population size within a given jurisdiction. The term is also applied to non-human animals, microorganisms, and pl ...

Mitochondrial DNA Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondrion, mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the D ...

analysis has now confirmed these subspecies to be separate species, with ''T. s. murphyi'' now simply '' Trachurus murphyi'', the Inca scad. The

divergence In vector calculus, divergence is a vector operator that operates on a vector field, producing a scalar field giving the rate that the vector field alters the volume in an infinitesimal neighborhood of each point. (In 2D this "volume" refers to ...

time of these two species was deemed relatively recent, at around 250,000 years ago. ''T. symmetricus'' is known commonly as the 'Pacific jack mackerel' in reference to its

distribution Distribution may refer to: Mathematics *Distribution (mathematics), generalized functions used to formulate solutions of partial differential equations *Probability distribution, the probability of a particular value or value range of a varia ...

, with the species often called simply 'jack mackerel' or 'mackereljack'

References

External links

* {{Taxonbar, from=Q2626960 Pacific jack mackerel Western North American coastal fauna Fish of Mexican Pacific coast Taxa named by William Orville Ayres Pacific jack mackerel