Main Article Content
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 yr–1 for the study lines. PT 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 PT anomalies show that during the ENSO events, values diminished by ~20% in the study area. Long-term PT 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 PT during 1997–98 was 0.014 GtC yr–1, increasing during 1999–2002 (0.023 GtC yr–1) 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 (–1), diminishing during the key year (0), and recovering one year after (+1) the event off Baja California. Complete (1950–2002) 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 × 103 tons after the 1976–77 period, with a recovering trend after 2000.
This is an open access article distributed under a Creative Commons Attribution 4.0 License, which allows you to share and adapt the work, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Figures, tables and other elements in the article are included in the article’s CC BY 4.0 license, unless otherwise indicated. The journal title is protected by copyrights and not subject to this license. Full license deed can be viewed here.