Fish Bulletin No. 73. Tagging Experiments on the Pacific Mackerel (Pneumatophorus diego)
Prior to 1928, the Pacific mackerel fishery was of minor importance, the catch being almost wholly absorbed by the fresh fish trade. Since that year, a large scale canning industry has developed in Southern California with an almost unlimited demand for fish. The bulk of the catch is processed in the Los Angeles Harbor area though large tonnages are handled at Newport Beach, some thirty miles to the south. Small amounts are canned at San Diego and at Ensenada, Mexico, the southern limit of the fishery. In Central California, mackerel are sometimes landed mixed with sardines (Sardinops caerulea) caught by the San Francisco and Monterey purse seine fleets. The quantity taken is rarely sufficient to warrant segregation for canning, and the mixed loads are for the most part reduced as "sardines." As a result, there is no record of the actual tonnage of mackerel handled at these ports.
The Southern California fishery for the canneries was at first prosecuted largely by net boats, first the lampara and later the purse seine fleet accounting for most of the catch. Since 1939, the emphasis has shifted to a large fleet of small "scoop" boats. The crews of these vessels, usually two or three men, fish with ground bait and dip the mackerel with a long-handled brail. The total catch has fluctuated widely from year to year with little relation to economic demand. Monthly landings reach a peak in the fall and winter months; there is a period of scarcity, apparently associated with spawning, which usually occurs in the spring but sometimes extends from mid-winter to early summer. For the period covered by this report the season is regarded as commencing in June and closing the following March.
The biological range of the species far exceeds the commercial, extending from the Gulf of Alaska southward into the Gulf of California. Mackerel are known to be abundant along much of the Lower California coast and heavy spawning occurs in Mexican waters. The population is apparently limited north of Central California and does not support a fishery above Monterey Bay.
The mackerel fleet operating out of Los Angeles Harbor (including for this report the City of Long Beach as well as the San Pedro, Wilmington and Terminal Island districts which comprise Los Angeles Harbor proper) exploits a large portion of the waters off Southern California. The purse seine fleet for both mackerel and sardines ranges from near Pt. Conception in the north to the Oceanside region in the south, and offshore to the Channel Islands. The scoop fleet covers Santa Monica Bay, the mainland coast as far south as Newport Beach, and offshore around Santa Catalina Island. Virtually the entire catch landed at Newport Beach is made by scoop boats fishing along the mainland coast between Huntington Beach and San Onofre and at Santa Catalina Island. At times this fleet will work south to Oceanside. Fishing at San Diego is carried on within twenty-five miles of port and is generally of minor significance.
At the present time (1948), there is no regular mackerel fishery in Central California. Until about 1941, a small hook-and-line fleet operated in Monterey Bay, supplying the fresh fish markets. The sardine fleet, which takes mackerel incidentally, operates between Pt. Reyes (30 miles northwest of San Francisco) and Pt. Buchon, about 100 miles south of Monterey. The San Francisco fleet fishes from north of Pt. Reyes to Monterey Bay.
With the tremendous increase in the commercial importance of mackerel, the California Division of Fish and Game instituted a research program designed to provide sufficient knowledge of the species to permit its proper management. Of basic importance was an understanding of the movements of the fish — whether the Southern California fishery was exploiting one or more of several independent populations existing throughout the range or whether and to what degree fish from other areas contributed to the local catch. The tagging program was devised originally in 1935 with this question in mind. It later seemed possible that tag returns might be used in studies of abundance and an intensified program was pursued in 1940 and 1941. With the outbreak of war, field work was greatly curtailed, though a few fish were tagged in the winter of 1942–43. Tags were collected through the 1946–47 season.
Three progress reports have been issued. These papers give more detailed information as to fishing methods and tagging techniques than is contained in the present publication, which does summarize the more pertinent data.
The tagging program demonstrated that mackerel from as far north as Oregon and as far south as the central portion of Lower California eventually entered the Southern California fishery. There was no evidence of a cyclic movement, although tagging in Lower California was not so conducted as to show such movement. There were indications of gradual dispersion over a period of years from the point of release. No fish were tagged south of central Lower California. There were few returned from this region and it seems probable that mackerel from farther south contribute little to the fishery.