8 Pacific mackerel Scomber japonicus
Distinguishing characteristics. The widely separated first and second dorsal fins serve to distinguish Pacific mackerel from all of the other tuna-like fishes that inhabit our waters, except the frigate or bullet mackerel. Pacific mackerel and bullet mackerel can be differentiated by counting either the dorsal or anal finlets. Pacific mackerel have typically five of each, while bullet mackerel typically have eight dorsal and seven anal finlets.
Distribution. A pelagic, schooling species normally found within 20 miles of shore, Pacific mackerel have known to range from the Gulf of Alaska to Banderas Bay, Mexico. They are seldom abundant north of Monterey, and fish from south of Magdalena Bay seldom, if ever, enter the California fishery.
Life history notes. The largest Pacific mackerel on record, nearly 25 inches long and weighing six and one-third founds, may be an exception. In general, they will weigh a pound and are 14 inches long when they are four years old. Annual growth begins to slow down at about this point and a 12-year-old mackerel may be shorter than 18 inches and lighter than two pounds. The oldest Pacific mackerel, out of 25,000 which have been aged, was in its 12th year when caught.
Off southern California, spawning normally reaches a peak during the early spring months, especially March, April, and May. Further south some spawning may take place during every month of the year, but it is at its best from December through March. Pacific mackerel eggs are about one-twenty-second of an inch (1.15 mm) in diameter and float free in the upper layers of the ocean - usually within 500 feet of the surface. At average water temperatures they will hatch in four or five days after spawning.
Larval and juvenile fish appear to be the most important natural food of Pacific mackerel, but there are times when they rely heavily on shrimp-like organisms known as euphausiids. They feed upon squid to a lesser extent. In turn, Pacific mackerel are preyed upon rather heavily by sea lions during infrequent periods when squid, which appear to be preferred by sea lions, are not locally available. White seabass, yellowtail, giant sea bass, and some sharks sometimes feed extensively on Pacific mackerel of medium-to-large size.
Fossil mackerel otoliths have been found in Pliocene and Miocene deposits in California; the Miocene deposits were laid down 20 to 40 million years ago.
9 California bonito (Sarda chiliensis)
Distinguishing characteristics. The California bonito is a member of the Spanish mackerel family which, in Mexican waters, includes such prizes as wahoo. The only other members of this family found off our shores are sierra and Monterey Spanish mackerel - rare summer visitors during some years. Bonito are the only tuna-like fishes on our coast that have oblique dark stripes on their backs.
Distribution. The distribution of this species appears to be discontinuous in the eastern Pacific Ocean. Those which are found along our shores are known to range (during some years) from Vancouver Island, British Columbia south to about Banderas Bay, Mexico. This species shows up again in the vicinity of Panama and range from there to off the coast of Chile. Bonito are the schooling species and are usually observed within a few miles of shore along the mainland coast and around the islands. They are seldom found in abundance north of Santa Monica Bay.
Life history notes. There is an unverified report of a 37-pound bonito, but specimens weighing as much as 25 pounds are rarely observed. Most of the fish caught by California fishermen weigh between 3 and 12 pounds. These fish are probably only one or two years old.
Bonito do not hatch every year in California, but successful spawning does occur further south each year. At some intervals spawning takes place and is successful in Santa Monica Bay and throughout much of the area between Long Beach and Dana Point. The bulk of such spawning appears to take place from late January through May. The free-floating eggs are about one-fifteenth of an inch in diameter (1.5 to 1.8 mm) and take about three days to hatch at average spring water temperatures.
A recently completed Peruvian study found that a 24—inch female weighing just over 6.5 pounds will spawn 500,000 eggs per season. Females first matured when they were between 18 and 21 inches long. Although spawning took place during 8 months of the year, most of it was during the Peruvian summer -October to February.
Young fish resulting from local spawnings are usually first observed when they are 6 to 10 inches long in the early summer months. These fish will often weigh one pound or more by the fall of the year. The preferred food of bonito appears to be small fish, such as anchovies and sardines. Occasionally, they rely heavily on squid in their daily diet.
Young bonito, less than a foot long are eaten by a group of voracious fish and mammals similar, if not identical, to those that eat Pacific mackerel. Large bonito would be difficult, if not impossible, for any but the largest marlin, tuna, giant sea bass, and such to handle.
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