Pacific Jack Mackerel - Taxonomy and Naming

Taxonomy and Naming

The Pacific jack mackerel is classified within the genus 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, the latter was accepted as 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'