Variability of community structure of Copepoda related to El Niño 1982–83 and 1987–88 along the west coast of Baja California Peninsula, Mexico

Copepod community structure and abundance of the most abundant species were studied during 15 cruises made between 1982 and 1989 along the west coast of the Baja California Peninsula, Mexico. The number of species and species diversity (Shannon's index) for each sampling station of the oceanographic cruises were obtained. Though the zone was dominated during the year by the tropical copepod component, similarities between El Niño 1982–83 and 1987–88 were observed. Tropical-equatorial populations were added to the regular tropical composition (50%) of the community of copepods resulting in a wide distribution of those populations in 1982–83 and in 1987–88. The scenario in 1984–89 (without 1987–88) was significantly different from both El Niños because of the sea surface temperature, the species diversity, and the tropical copepod component, although 1982 was similar to 1985 in diversity index and number of species. Environmental conditions prevailing along the west coast of Baja California during El Niño indicate that in 1982–83 the effect on the copepod community was greater than during the 1987–88 event.