Long-term time series of total primary production (PT) from 1969 through 2002, associated with ENSO (El Niño/Southern Oscillation) events are presented for the region off northern Baja California. PT was calculated using an empiric model in six inshore and offshore grids of the CalCOFI-IMECOCAL network in the southern California Current. In general, PT anomalies were positive from 1970 to 1975, with a period average of 0.024 GtC yrâ1 for the study lines. PT changed to negative anomalies after ENSO 1976â77, with a decrease in productivity for at least 20 years, reinforced by the ENSO events of 1982â84, 1987â88, 1992â93 and 1997â98. Annual time series of PT anomalies show that during the ENSO events, values diminished by ~20% in the study area. Long-term PT changes (1976â97) originated a reduction of 0.007 GtC yrâ1 (~70%), in relation to the higher production of the early 1970s (1970â75). Mean PT during 1997â98 was 0.014 GtC yrâ1, increasing during 1999â2002 (0.023 GtC yrâ1) toward similar values calculated for the early 1970s. Superposed Epoch Analysis proved the statistical association between the ENSO events and PT, with the probability of high production one year before (â1), diminishing during the key year (0), and recovering one year after (+1) the event off Baja California. Complete (1950â2002) PT time series showed greatest variance in the 1.43-year period. Small pelagic fish biomass estimated for inshore stations of lines 90 and 107 dropped below 200 Ă 103 tons after the 1976â77 period, with a recovering trend after 2000.