Size structure of populations (shell length in mm) and oocyte size (in µm) distribution of three hydrothermal vent gastropod species (Lepetodrilus schrolli, L. fijiensis and Shinkailepas tollmanni) of the South West Pacific back-arc basins. Individuals were collected in Bathymodiolus spp. and Ifremeria nautilei habitats at several vent sites in the Manus, North Fiji, Futuna and Lau back-arc basins during the CHUBACARC cruise in 2019. These data were collected through stereoscopic microscope observations and hostological analyses on several individuals of each species.