LAUSR

Abstract We studied the abundance, size and growth rates of Engraulis anchoita larvae during the end of the species’ spawning season in relation to environmental variables. Two sampling transects, one in Peninsula Valdes (northern transect: NT) and the other in Isla Escondida (southern transect: ST), with four stations each, were established in late summer. Both locations are characterized by high concentrations of E. anchoita larvae in spring, strongly associated with the presence of frontal waters, at the beginning of the species’ spawning season. Zooplankton and ichthyoplankton were sampled, and temperature profiles and chlorophyll-a satellite images were analyzed for each sampling station. Zooplankton samples were divided in size fractions, and composition and abundances were estimated. Standard length (SL), ontogenetic stages, and abundance (including eggs) were estimated. Additionally, age and growth rates were determined by otolith analysis. Two different scenarios were observed in both transects. In the NT, a frontal structure was found, while at the ST, the water column was completely homogeneous. Total zooplankton abundance was maximum at frontal waters, with 22,195 ind. m−3, being the small size fraction (