Pacific jack mackerel
Encyclopedia
The Pacific jack mackerel,Trachurus symmetricus (also known as the Californian jack mackerel or simply jack mackerel), is an abundant species
of pelagic marine
fish
in the jack family, Carangidae
. The species is distributed along the western coast of North America
, ranging from Alaska
in the north to the Gulf of California
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 Trachurus murphyi, which was once thought to be a subspecies
of T. symmetricus, and inhabits waters further south. Pacific jack mackerel travel in large schools
, ranging up to 600 miles offshore and to depths of 400 m, generally moving through the upper part of the water column.
Trachurus
, commonly known as the horse mackerels or jack mackerels. Trachurus is part of the jack family Carangidae
, a group of Perciform fish in the suborder Percoidei
. Recent genetic studies
have divided the Carangidae into four subfamilies, with the genus Trachurus falling into the 'Caranginae' (or tribe
Carangini), being most closely related to the 'scads' of the genera Decapterus
and Selar.
The species was first scientifically described by William Orville Ayres
in 1855 based on the holotype
specimen taken from San Francisco Bay
, California
. 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
, which under the ICZN
rules classifies as a junior synonym, 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 subspecies
; 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 it was accepted that the latter was a valid combination, with Trachurus symmetricus murphyi considered to be a southern subspecies population
. Mitochondrial DNA
analysis has now confirmed these subspecies to be separate species, with T. s. murphyi now simply Trachurus murphyi, the Inca scad. The divergence
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, with the species often called simply 'jack mackerel' or 'mackereljack'
The Pacific jack mackerel is very similar to all other members of Trachurus and a number of other carangid genera, having an elongate, 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 common at below 55 cm. There are two separate dorsal fin
s, the first composed of eight spines while the second slightly lower fin consists of 1 spine followed by 31 to 35 soft rays. The anal fin is composed of two spines anteriorly 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 is strongly forked, typical amongst the Carangidae, while the ventral fin consists of 1 spine and five soft rays. The pectoral fin terminates before the front of the anal fin, having 22 to 24 rays in total. The lateral line
dips strongly after the pectoral fin, having 50 to 53 scales
on the upper section and 43 to 52 keeled scute
s posteriorly. The species teeth are minute, with a patch of teeth on the tongue
in a narrow club shaped strip. There are 24 vertebrae 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
to dusky, although caudal fin may be yellow to reddish.
from Alaska
in the north, down the western North American seaboard to the Baja California peninsula
in the Gulf of California
. It has been reported as far south as the Galápagos Islands
, however at these latitudes it would be sympatric with T. murphyi, possibly resulting in confusion of the two species. Pacific jack mackerel occur in both pelagic 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.
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.
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.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of pelagic marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
in the jack family, Carangidae
Carangidae
Carangidae is a family of fish which includes the jacks, pompanos, jack mackerels, and scads.They are marine fish found in the Atlantic, Indian and Pacific Oceans...
. The species is distributed along the western coast of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, ranging from Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
in the north to the Gulf of California
Gulf of California
The Gulf of California is a body of water that separates the Baja California Peninsula from the Mexican mainland...
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
Trachurus
Jack mackerels are marine fishes in the Trachurus genus of the Carangidae family. The type species of the genus is the Atlantic horse mackerel, Trachurus trachurus. The name of the genus is derived from the Greek word trachys, meaning "rough", and the Greek word oura, meaning "tail"...
, especially Trachurus murphyi, which was once thought to be a subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
of T. symmetricus, and inhabits waters further south. Pacific jack mackerel travel in large schools
Shoaling and schooling
In biology, any group of fish that stay together for social reasons are said to be shoaling , and if, in addition, the group is swimming in the same direction in a coordinated manner, they are said to be schooling . In common usage, the terms are sometimes used rather loosely...
, ranging up to 600 miles offshore and to depths of 400 m, generally moving through the upper part of the water column.
Taxonomy and naming
The Pacific jack mackerel is classified within the genusGenus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Trachurus
Trachurus
Jack mackerels are marine fishes in the Trachurus genus of the Carangidae family. The type species of the genus is the Atlantic horse mackerel, Trachurus trachurus. The name of the genus is derived from the Greek word trachys, meaning "rough", and the Greek word oura, meaning "tail"...
, commonly known as the horse mackerels or jack mackerels. Trachurus is part of the jack family Carangidae
Carangidae
Carangidae is a family of fish which includes the jacks, pompanos, jack mackerels, and scads.They are marine fish found in the Atlantic, Indian and Pacific Oceans...
, a group of Perciform fish in the suborder Percoidei
Percoidei
Percoidei is one of eighteen suborders of bony fish in the order Perciformes. Many commercially harvested fish species are contained in this suborder, including the snappers, jacks, whitings, groupers, bass, perches and porgies.-Divisions:...
. Recent genetic studies
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
have divided the Carangidae into four subfamilies, with the genus Trachurus falling into the 'Caranginae' (or tribe
Tribe (biology)
In biology, a tribe is a taxonomic rank between family and genus. It is sometimes subdivided into subtribes.Some examples include the tribes: Canini, Acalypheae, Hominini, Bombini, and Antidesmeae.-See also:* Biological classification* Rank...
Carangini), being most closely related to the 'scads' of the genera Decapterus
Decapterus
Decapterus is a genus of marine fishes in the family in the jack family, Carangidae. They are commonly known as mackerel scads, and round scads. They are found throughout the world....
and Selar.
The species was first scientifically described by William Orville Ayres
William Orville Ayres
William Orville Ayres was an American physician and ichthyologist. Born in Connecticut, he studied to become a doctor at Yale University School of Medicine....
in 1855 based on the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
specimen taken from San Francisco Bay
San Francisco Bay
San Francisco Bay is a shallow, productive estuary through which water draining from approximately forty percent of California, flowing in the Sacramento and San Joaquin rivers from the Sierra Nevada mountains, enters the Pacific Ocean...
, California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
. 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
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
, which under the ICZN
International Code of Zoological Nomenclature
The International Code of Zoological Nomenclature is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...
rules classifies as a junior synonym, 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 subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
; 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 it was accepted that the latter was a valid combination, with Trachurus symmetricus murphyi considered to be a southern subspecies population
Population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...
. Mitochondrial DNA
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
analysis has now confirmed these subspecies to be separate species, with T. s. murphyi now simply Trachurus murphyi, the Inca scad. The divergence
Divergence
In vector calculus, divergence is a vector operator that measures the magnitude of a vector field's source or sink at a given point, in terms of a signed scalar. More technically, the divergence represents the volume density of the outward flux of a vector field from an infinitesimal volume around...
time of these two species was deemed relatively recent, at around 250 000 years ago.
T. symmetricus is known commonly
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
as the 'Pacific jack mackerel' in reference to its distribution, with the species often called simply 'jack mackerel' or 'mackereljack'
Description
It is a medium to large sized fish, growing to a maximum known length of 81 cm (32 in), although more common at below 55 cm. There are two separate dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
s, the first composed of eight spines while the second slightly lower fin consists of 1 spine followed by 31 to 35 soft rays. The anal fin is composed of two spines anteriorly 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 is strongly forked, typical amongst the Carangidae, while the ventral fin consists of 1 spine and five soft rays. The pectoral fin terminates before the front of the anal fin, having 22 to 24 rays in total. The lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...
dips strongly after the pectoral fin, having 50 to 53 scales
Scale (zoology)
In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...
on the upper section and 43 to 52 keeled scute
Scute
A scute or scutum is a bony external plate or scale, as on the shell of a turtle, the skin of crocodilians, the feet of some birds or the anterior portion of the mesonotum in insects.-Properties:...
s posteriorly. The species teeth are minute, with a patch of teeth on the tongue
Tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...
in a narrow club shaped strip. There are 24 vertebrae in total.
Pacific jack mackerel are metallic blue to olive-green dorsally, becoming more silvery ventrally, before transitioning to a white belly
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
. 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
Hyaline
The term hyaline denotes a substance with a glass-like appearance.-Histopathology:In histopathological medical usage, a hyaline substance appears glassy and pink after being stained with haematoxylin and eosin — usually it is an acellular, proteinaceous material...
to dusky, although caudal fin may be yellow to reddish.
Distribution and habitat
The Pacific jack mackerel is distributed through the eastern Pacific OceanPacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
from Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
in the north, down the western North American seaboard to the Baja California peninsula
Baja California Peninsula
The Baja California peninsula , is a peninsula in northwestern Mexico. Its land mass separates the Pacific Ocean from the Gulf of California. The Peninsula extends from Mexicali, Baja California in the north to Cabo San Lucas, Baja California Sur in the south.The total area of the Baja California...
in the Gulf of California
Gulf of California
The Gulf of California is a body of water that separates the Baja California Peninsula from the Mexican mainland...
. It has been reported as far south as the Galápagos Islands
Galápagos Islands
The Galápagos Islands are an archipelago of volcanic islands distributed around the equator in the Pacific Ocean, west of continental Ecuador, of which they are a part.The Galápagos Islands and its surrounding waters form an Ecuadorian province, a national park, and a...
, however at these latitudes it would be sympatric with T. murphyi, possibly resulting in confusion of the two species. Pacific jack mackerel occur in both pelagic 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.
Relationship to humans
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 horse mackerel, and had little market appeal. However, in 1948, the US. Pure Food and Drug Administration decided to allow the use of "jack mackerel" on all labeling, and it 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, made the fish gain importance . In the past mackerel consumption was considered a sign of low income. In the American segregated Southern states, it was often associated with black Americans. Today, most of these stereotypes are gone.Other
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.