Larval fish assemblages in waters off the central Pacific coast of Mexico

Spatial and seasonal variation of the ichthyoplankton assemblageswas analysed using monthly samples collected during a 1 yearcycle off the central Pacific coast of Mexico. Zooplankton sampleswere collected at 12 stations during 11 months, from December1995 to December 1996. The analysis of coastal oceanographicconditions revealed two main seasonal patterns, one relatedto the California Current influence and the other a tropicalone. A temporal recomposition of the ichthyoplankton assemblageswas found to be related to each oceanographic pattern. Duringthe California Current period (January–May) the larvalfish assemblage was respresented mainly by Auxis sp., Bentosemapanamense, Cetengraulis mysticetus, Opistonema sp., Symphuruselongatus, Gobionellus sp., Dormitator latifrons and Bregmacerosbathymaster. The tropical season assemblage (July, October andNovember) was represented by Harengula thrissina, Euthynnuslineatus, Vinciguerria lucetia, Syacium ovale, and representativesof the Eleotridae and Pomacentridae. An inshore–offshoregradient was observed during the tropical oceanographic periods,with a thermic stratification of the water column over the shelf.Conversely, during the California Current period, with coastaladvective processes, the assemblages of fish larvae were morehomogeneous. Although a mixed, richer faunistic compositionwas expected in this transitional area, the overall biogeographicaffinity of the surveyed community remained stable even in contrastingconditions.