A review of the verified reports to date of Architeuthis dux showed that 26% (148 specimens) of worldwide reports were derived from the north-eastern Atlantic. Biological data are presented on fifteen females and two males from Asturian waters (Northern Spain). Both males represent the two first records captured off the Iberian Peninsula. Immature and maturing females ranged from 60 to 140 Kg total weight, whilst mature males weights were 42 and 66 Kg. The peculiar observation of spermatophores embedded in the skin of one of the males near the proximal part of the ventral, ventro-lateral and dorso-lateral arms is discussed. A comparison was undertaken of several morphometric measurements between both sexes and between these two males and five other north-eastern Atlantic males from which data were available. Two incidents of multiple strandings affecting nine specimens in 2001 and 2003 appear to be linked spatially and temporally to geophysical prospecting using air-gun arrays in the Bay of Biscay. Here we present evidence of acute tissue damage in the stranded and surface-floating giant squids. The incidence of such cases during two research cruises contemporary with integrated geological and geophysical studies of the continental margin of the Cantabric Sea indicate that acoustic factors could have caused or contributed to the organ and tissue lesions that probably caused the deaths of these animals. Thus, further environmental regulation of such activity may be warranted to protect animals of the continental slope.