Based on previous knowledge on the use of acoustics to assess hake larvae, a study was conducted in the Galician shelf (NW Spain) during winter (February-March 2012). An echosounder operating with 18, 38, 70, 120 and 200 kHz split-beam, hull-mounted transducers was employed. We analyzed the acoustic records in order to describe vertical and horizontal distribution patterns of fish larvae aggregations (mainly of the gadoid species blue whiting Micromesisitius poutassou and European hake Merluccius merluccius). Net sampling revealed that acoustic back-scattered energy at 38 and 70 kHz was roughly proportional to the density of Micromesistius poutassou larvae of 3.5mm and larger, while scattering due to zooplankton appear to be negligible at those frequencies. The results described herein suggest that echo-sounding data may provide a viable methodology for the study of spatial and temporal changes and trends in abundance of gadoid larvae, in particular blue whiting. In addition, the characterization of fish larvae aggregation will allow the mapping of their distribution by the analysis of previous acoustic databases.