Larval fish assemblages off central Chile upwelling ecosystem

Spatial (both vertical and horizontal) and seasonal differences were detected in larval fish assemblages from samples collected off central Chile. Vertically-stratified sampling was carried out over the slope and continental shelf off Talcahuano in central Chile, during October 1998 and July 1999 to examine differences in larval fish assemblages. During October, the entire water column in the shelf and slope stations was characterized by cold and saltier waters, indicative of a recent upwelling event; during this period the larval fish assemblage was structured by time of the day in the shelf station. This assemblage was dominated by larvae of the mesopelagic lightfish Maurolicus parvipinnis and anchoveta Engraulis ringens. By contrast, ichthyoplankton was vertically structured in the slope station, showing different taxa associations in function of the depth (largely dominated by M. parvipinnis and the myctophid Hygophum bruuni). During July 1999, oceanographic conditions were characterized by higher surface temperatures, thermal inversion and a low salinity surface layer (33.6-33.8). Larval fish assemblages from slope and shelf were vertically stratified, and were aggregated below the halocline. Larval E. ringens and H. bruuni were highly abundant in both stations, and larvae of several taxa of subtidal/intertidal habitat (Hypsoblennius sordidus, Sebastes capensis) were collected over the shelf. During both periods the oceanographic features affecting the structure of larval fish assemblages off central Chile changed, wich was more noticeable during July (effects of the low salinity layer) than October (presence of recently upwelled waters).