Eight acoustic surveys were carried out in the Bay of Biscay, during 1989-94, to study the distribution and abundance of anchovy (Engraulis encrasicolus, L.) in that area. Acoustic data were stored using the INES/MOVIES acquisition and processing system. Species-specific distribution patterns were confirmed through complementary sampling with a mid-water trawl. This paper summarises the combination of technical procedures used for acoustic assessments, and the results of acoustic surveys in the Bay of Biscay that pertain to the dynamics of this stock. Information is presented on the distribution and abundance of anchovy and co-occuring species, and on the movement patterns detected within the pelagic fish community, in relation to environmental conditions. A comparative analysis of the vertical distribution of echo traces revealed some species-specific preferences. Beyond the stock-assessment possibilities, experiments showed that acoustic survey methods can provide considerable knowledge used for ecological research.