We studied age, growth, and reproduction of the Pacific mackerel Scomber japonicus from the Gulf of California. Age determinations from otoliths showed that the Pacific mackerel in the Gulf ranged from 0-9 yrs old. The minimal size at recruitment into the fishery is 83 mm in
standard length (SL) prior to attaining 1 yr in age, and 50% of the recruitment occurs prior to 193 mm in SL which corresponds to an age of 3.3 yrs. Growth is well described by the von Bertalanffy equation SL = 281.6 (1-e-0.22 (Age+3.5)). The reproductive season is from November
to April and spawning occurs mainly in the area of Yavaros. During spawning, the sex ratio did not vary from 1:1 for 5 mm size classes from 145-315 mm in SL. Data on the geographical and temporal distribution of different maturity stages suggested a spawning migration toward the south of the
Gulf of California. Our data support the hypothesis that the spawning stock in the Gulf of California extends from north of Isla Tiburón and Isla Angel de La Guarda to Bahía Magdalena.
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