California yellowtail
Distinguishing characteristics. The California yellowtail is 1 of 12 members of the jack family that are known to inhabit the waters of the State. Only 2 of these 12, jack mackerel and yellowtail, are ever found off our shores in any abundance. The horizontal dark streak that runs through the eye and along the side of the body, the low first dorsal fin, and the relatively short pectoral fins easily distinguish the California yellow-tail from the jack mackerel. Yellowtail less than five inches in length have 9 to 11 dark vertical bars along their sides.
Distribution. The California yellowtail has been reported from Monterey Bay south to Cape San Lucas, Baja California, and north again throughout much of the Gulf of California. During recent years they have been caught only occasionally north of Point Conception. Yellowtail do not normally spawn off California and older fish are in our waters only seasonally during most years.
Life history notes. The largest recorded California yellow-tail is an 80-pound fish that was caught at Guadalupe Island a number of years ago. Most of the fish caught by California fishermen weigh between 10 and 20 pounds and are three to seven years old. In a recently completed study, the oldest fish for which a reliable age could be determined was a 12-year-old 35-pounder.
Many yellowtail will spawn when two years old and all will spawn when three. Two- and three-year-old fish weigh about 7 and 10 pounds, respectively. The ovaries of a three-year-old female contain approximately 1,500,000 eggs. The spawning season normally runs from June through September with July and August best.
Most yellowtail have to travel several hundred miles before they are caught by California-based sportfishermen. Tagging results show that nearly all of the fish in our waters come from the Cedros Island area of Baja California. At least one fish made a 370-mile trip north before he was caught.
Yellowtail feed upon whatever natural foods in the areas in which they are found. In Southern California waters they feed mostly upon anchovies and sardines; further south the diet consists to a great extent of pelagic red crabs, squid, and such.
7 Pacific jack mackerel Trachurus symmetricus
Distinguishing characteristics. Of the 12 kinds of jacks that have been taken in California waters, only jack mackerel and Mexican scad have sharp ridges on each side of the base of the tail. These ridges are modified lateral line scales. Mexican scad at first glance would appear to be inseparable from jack mackerel. However, in the jack mackerel the last dorsal and anal fin rays are integral parts of the fins that precede them. On the Mexican scad, these last fin rays are rather widely separated from the preceding rays and are not joined to them in any way. There are only a few authenticated records of Mexican scad in California waters, however.
Distribution. Jack mackerel have been taken along the mainland coast of North America from British Columbia south to Acapulco, Mexico, but they probably are not abundant south of Magdalena Bay. They have been captured on frequent occasions as far as 600 miles off the coast of Southern California. They are a pelagic, schooling species, and are most often found at or near the surface in close proximity to the mainland shore, the islands, or offshore banks.
Life history notes. A 332-inch-long fish that weighed just a fraction of an ounce more than five pounds appears to be a record specimen. The earbones of this fish indicated an age of at least 27 years. Other large jack mackerel have been reliably aged at more than 30.
Fifty percent of the two-year-old female jack mackerel (10 inches long to the fork of the tail) are sexually mature. Till age three (14 inches long) are 100 percent of the female mature. Spawning takes place over an extensive area which is centered between 80 and 240 miles from shore. Off southern California the spawning season is mostly confined to the five-month period, March through July. A single female will normally spawn more than once during the season and the eggs, which are about one-twenty-fifth of an inch in diameter, float free in the upper water layers of the ocean - usually within 300 feet of the surface. At average ocean temperatures the eggs hatch in four to five days. The newly hatched larva is about one-twelfth of an inch in total length.
Carefully conducted food studies indicated that more than 90 percent of the identifiable items found in the stomachs of jack mackerel were two kinds of crustaceans (euphausiids and large copepods) and small pelagic mollusks known as pteropods. At times, jack mackerel are known to feed heavily upon anchovies, lanternfish, or juvenile squid. Jack mackerel are eaten by sea lions, some kinds of dolphins, and several species of large fishes such as yellowtail, white seabass, giant sea bass, angel sharks and blue sharks. Small jack mackerel are often important in the diet of albacore. A jack mackerel otolith was found in an Indian midden at La Jolla recently.