Ichthyoplankton distribution off the Peninsula de Mejillones, Chile (23° S, 71° W), under variable hydrographic conditions during the austral summer and winter of the 1997 El Niño

Abstract

This paper identifies the larval fish community distribution, emphasizing non-commercial species, in the coastal zone and the adjacent oceanic area off the Peninsula de Mejillones (23° S, 71° W) during the 1997 El Nino. We performed one survey in the austral summer (January) and one in the austral winter (July). In January, cold, upwelled water dominated the area off the Peninsula de Mejillones with a cold-water filament extending 60 nm offshore. In July, warm Subtropical Surface Waters affected the area. We identified a total of 56 taxa, which included taxa from different adult habitats (coastal, epipelagic, epi-mesopelagic and mesopelagic). The most abundant species were Engraulis ringens (18% and 21%), Bathylagus sp. (4% and 5%), Diogenichthys laternatus(12% and 39%), Lampanyctus parvicauda (9% and 2%), Triphoturus mexicanus (14% and 3%) and Vinciguerria spp. (21% and 23%), in January and July, respectively. A multidimensional scaling (MDS) ordination and similitude dendograms revealed changes in the larval fish community structure influenced by hydrographic conditions. The rank correlations between the assemblage similarity matrix and the physical variables matrix indicate the importance of the distance from shore and production processes (represented by chlorophyll-a) on the assemblage distributions. Off the Mejillones' coast, there is a complex spatial and temporal hydrographic system where ichthyoplankton of coastal and oceanic fish species coexist. Despite both short-term and longer-term disruptive oceanographic processes (e.g., mesoscale filaments, El Nino events), it seems that the numerically dominant species persist in the area due to their various behavioral strategies and physiological adaptations.