Latin name

Trachurus symmetricus

Other names

Horse mackerel, jack mackerel, jackfish, mackereljack, scad; Spanish: charrito, chicharro.

Identification

The body of the Pacific horse mackerel is somewhat compressed and elongated, and the tail is broad and deep. The dorsum coloration is from blue-blue to olive-green, changing to silver on the belly. The top of the snout and the base of the pectoral fins are black. The gill cover has a black spot. The last dorsal and anal soft rays are attached to the body or rarely separated from the fins, and the sides are covered with enlarged scales. The Pacific horse mackerel bears a resemblance to the Mexican scad, but the enlarged scales distinguish it, as do the last attached dorsal and anal fin rays. In Mexican scad, the rays are individual fins.

Distribution

In the eastern Pacific, Pacific jack mackerel are found from southeast Alaska to southern Baja California, extending all the way to the Gulf of California, Mexico. They can be found near Acapulco, Mexico, and from the Galápagos Islands. Occurs in the northeastern Pacific along the western shores of North America on the shelf and over submarine banks from the Gulf of Alaska north to southern California (Cape San Lucas, Mexico).

Habitat

Marine pelagic gregarious fish. A good swimmer, the vertical range is 250 m. Pacific horse mackerel are often found at sea in large aggregations. Adults are found up to 500 miles offshore and at depths of up to 150 feet. Young fish stay near kelp and under piers, while larger fish often go offshore or northward.

Size

The maximum length of the horse mackerel is 76 cm. It has a significant growth rate, growing up to 20 cm in the 1st year of life and 35 cm in length by the 4th year. In the southern part of the range, offshore California and to the south, junior mackerel up to 30 cm in length at the age of 3 years are found in catches. At the northern limit of the range, offshore Washington and Oregon, in contrast, older horse mackerel 37 cm or more in length and 6 years of age or older are caught. Here, the basis of catches is 54 cm long fish 9-10 years old, with fish of maximum length (greater than 70 cm) occurring in small numbers in the shelf catches only during the early summer months. Outside the shelf, in the open ocean at latitudes of 27-35°N and up to 200 nautical miles from the continent's shores, mackerel were caught at least 36 cm long and over 5 years old. Pacific horse mackerel can weigh 4 to 5 pounds and live 20 to 30 years.

Life history and Behavior

Sexual maturity in the Pacific horse mackerel comes early. Half of the females are ready to spawn at age 2, and all fish spawn by age 3. Spawning takes place from March through June over a wide area, from 80 to more than 240 miles offshore. In the open ocean during the spring-summer period, jack mackerel make daily vertical migrations: rising to the surface at night, staying in the 5-70 m layer, and descending to a depth of 120 m in the daytime. Adult horse mackerel of older age groups with a length of 37 cm and more at the age of 6 years and older are characterized by long seasonal migrations. In winter, it inhabits shelf waters of the U.S. and Mexico, staying within 50 nautical miles from the shore and not going further north than 40°N. In spring and summer, aggregations of large horse mackerel migrate north to the coast of British Columbia and the Gulf of Alaska (to 58°N), moving along a broad front and beyond the 200-mile zone. The length of these migrations reaches 800 nautical miles from south to north, with fish moving constitutes 13-14 nautical miles per day. After spawning around the subarctic front, intensive fattening of these mackerel occurs, its main feeding concentrations are noted on the shelves of Oregon and Washington states.

Food and feeding habits

Young horse mackerel up to 30 cm in length at the age of up to 3 years feed mainly on mesoplankton, mainly euphausiids, and to a lesser extent on copepods and wing-footed mollusks. The adult horse mackerel is an optional fish-eating predator. The main food of older horse mackerel is macroplankton, including large euphausiids. At times on the shelf, it hunts exclusively for small squid and anchovies, and in the open ocean outside the shelf - for shiner anchovies.

Reproduction

Spawning in portions, and the eggs hatch at night. Mass onset of sexual maturity is noted at a length of 25 cm in the 3rd year of life. Spawning takes place from January to November, the most intensive spawning is observed from March to July. The main spawning grounds are located off the coast of the California Peninsula, at 30-35°N, 80-400 nautical miles offshore, at these latitudes in the open ocean summer spawning is recorded up to 150°W. In the north of the range off the coast of Oregon and Washington states, mackerel spawning has been recorded up to 1000 nautical miles from shore. The eggs are pelagic, non-sticky, spherical, about 1 mm in diameter, developing in the upper layers of water. The incubation period lasts about 2 days at 17.9°С and 4 days at 14.5°С. At the time of hatching, the larvae of mackerel are about 2 mm long. It is believed that from the main spawning areas, the larvae are drifting at a distance of up to 400 nautical miles from the shore. Young horse mackerel are mostly 19-20 cm in length at age 1, forming mixed clusters with a few fish up to 30 cm in length at age 3, throughout the year off the California coast - from Cape Concepción (south of 35° N) and along the California Peninsula to Cape San Lucas, its main aggregations occur on the shelf of the California Peninsula, as well as over the underwater banks at a distance of 120-150 nautical miles from shore. Here this mackerel fattens, making small movements between islands and along the coast. It is assumed that the juveniles move from the spawning areas to the shore and then move away from the shore again as they grow.