AGE, GROWTH, AND REPRODUCTION OF PACIFIC MACKEREL SCOMBER-JAPONICUS IN THE GULF-OF-CALIFORNIA

We studied age, growth, and reproduction of the Pacific mackerel Scomb er japonicus from the Gulf of California. Age determinations from otol iths 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 stan dard length (SL) prior to attaining 1 yr in age, and 50% of the recrui tment 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 spawni ng, 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 d ifferent maturity stages suggested a spawning migration toward the sou th of the Gulf of California. Our data support the hypothesis that the spawning stock in the Gulf of California extends from north of Isla T iburon and Isla Angel de La Guarda to Bahia Magdalena.