The Pélagiques Gascogne (PELGAS, Doray et al., 2000) integrated survey aims at assessing the biomass of small pelagic fish and monitoring and studying the dynamics and diversity of the Bay of Biscay pelagic ecosystem in springtime. PELGAS has been conducted within the EU Common Fisheries Policy Data Collection Framework and Ifremer’s Fisheries Information System. Details on survey protocols and data processing methodologies can be found in Doray et al., (2018a, 2021). This dataset comprises the mean length-at-age (cm) and weight-at-age (g) estimated annualy since 2000 for anchovy and sardine, based on PELGAS survey data. Both indices were weighted by fish abundance per length class, and are provided with an estimation error (coefficient of variation in %). Indices were produced following a standard methodology implemented in the EchoR R package (Doray et al. 2013). Those estimates have been validated by the ICES WGACEGG group and provided to the ICES WGHANSA group for stock assessment purposes. Data have been used in Doray et al., 2018b.