Interannual changes in the reproductive pattern of the brown shrimp, Farfantepenaeus californiensis, a commercially important marine crustacean, were analysed as a function of sea water temperature. Daily samples of gravid females from 1979 through 1994 and monthly sea water temperatures were examined. The results show a high interannual variability of the reproductive period with two patterns; one in which spawning occurs throughout the year, the other with two peaks of mass spawning. The first of the two peaks is the more intense, occurring from March to May; the other is in October and November and is less intense. The extended spawning period occurs under warmer conditions and is probably associated with El Niño events. The pattern with two peaks is associated with average sea water temperatures. Occurrence of one pattern or the other may have significant consequences for managing this fishery
