Abstract

HERNANDEZ DE LA TORRE, Benigno; GAXIOLA-CASTRO, Gilberto  and  NAJERA-MARTINEZ, Sila. ENSO effects on primary production off Baja California. Cienc. mar [online]. 2004, vol.30, n.3, pp.427-441. ISSN 0185-3880.

Long-term time series of total primary production (P_T) from 1969 through 2002, associated with ENSO (El Niño/Southern Oscillation) events are presented for the region off northern Baja California. P_T was calculated using an empiric model in six inshore and offshore grids of the CalCOFI-IMECOCAL network in the southern California Current. In general, P_T anomalies were positive from 1970 to 1975, with a period average of 0.024 GtC yr^-1 for the study lines. P_T changed to negative anomalies after ENSO 1976-77, with a decrease in productivity for at least 20 years, reinforced by the ENSO events of 1982-84, 1987-88, 1992-93 and 1997-98. Annual time series of P_T anomalies show that during the ENSO events, values diminished by ~20% in the study area. Long-term P_T changes (1976-97) originated a reduction of 0.007 GtC yr^-1 (~70%), in relation to the higher production of the early 1970s (1970-75). Mean P_T during 1997-98 was 0.014 GtCyr^-1, increasing during 1999-2002 (0.023 GtCyr^-1) toward similar values calculated for the early 1970s. Superposed Epoch Analysis proved the statistical association between the ENSO events and P_T, with the probability of high production one year before (-1), diminishing during the key year (0), and recovering one year after (+1) the event off Baja California. Complete (1950-2002) P_T 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 x 10³ tons after the 1976-77 period, with a recovering trend after 2000.

Keywords : total primary production; ENSO; Superposed Epoch Analysis; California Current; Baja California.