Inter-Research
Marine Ecology Progress Series

ABSTRACT: Changes in the community structure and distribution patterns of 20 species of euphausiids collected during 6 oceanographic cruises along the southwest coast of Baja California during El Niño Southern Oscillation (ENSO) 1986-1987 were compared with the data from 5 cruises made during ENSO 1982-1983. The possible existence of different influences of environmental conditions on the distribution, abundance, and community structure of euphausiids during the 2 periods was assessed. Although a time series of surface temperature (SST) from 3 latitudinal regions along the west coast of Baja California during 1980 and 1990 showed no evidence of a long-term warming in 1986 and early 1987, a positive SST anomaly (1*C) was observed during the second half of 1987, reaching latitude 26*N. The composition of species during this study showed a high proportion of tropical and equatorial endemic Eastern Tropical Pacific (ETP) species, north and south margin ETP proliferator species, and warm water cosmopolitan species. There was a scarcity of California Current terminus species. Euphausiapacifica Hansen and Thysanoessagregaria G. O. Sars, 2 temperate species, were considered to have moved from their reproductive areas. Nyctiphanessimplex Hansen dominates the euphausiid fauna of the west coast of Baja California and was most plentiful near the shore. Its reproductive activity was mainly in upwelling regions. Seasonal and latitudinal variability of the intensity of the upwelling along the peninsula could have a strong influence on the range of distribution of its highest abundance centers. The southern region was dominated by tropical and equatorial endemic ETP-adapted species showing reproductive activity. Compared to ENSO 1982-1983, the influence of ENSO 1986-1987 on the community of euphausiids in the southern part of Baja California was small.

KEY WORDS: Euphausiid . ENSO . Community structure . Baja California . Mexico

Published in MEPS Vol. 120 (1995) on April 20
Print ISSN: 0171-8630; Online ISSN: 1616-1599. Copyright © Inter-Research, Oldendorf/Luhe, 1995