For this study AZTI has used the Vizconde de Eza research vessel, belonging to the Secretaría General de Pesca Marítima (General Secretary of Sea Fisheries) and considered to be one of the most advanced oceanographic ships in the world. , ,In this seasons' evaluation different tasks were carried out for the various projects financed by Basque Governments Department of Agriculture and Fisheries and by the European Union, within the National Sampling Plan: - Assessing the anchovy biomass in the Bay of Biscay for 2004,- Assessing the incidence of eggs and adult population for jack mackerel and common mackerel to help the estimatation of their biomass. Sampling area:,· Total area explored was 53,285 km2 ,· Egg lying area was 23,124 Km2 Preliminary assessment and results,From the preliminary results we can say that the abundance of eggs is low compared to previous years. Thus, we can estimate that the biomass total quantity existing, by weight of the anchovy population in the sea - in the Bay of Biscay in the spring of 2004 will be less than the yearly average that has been recorded since 1989. Moreover, the catches in 2004 were about 7,000 tonnes which, despite being greater than the previous year (some 3,000 tonnes), were considerably less than the yearly average of 13,000 tonnes over the last eleven years. The low abundance of anchovy eggs could have been due, not only to a low anchovy biomass, but also to a low fecundity rate (the production of eggs per anchovy), possibly caused by the low temperatures of the waters recorded during the BIOMAN season (average of 13.7ºC). This preliminary data will be ratified after the histological analysis of the adult anchovy samples, which will enable the researcher to make a definitive estimate of the anchovy biomass for this year.