The shell parameters length, height and width were measured for specimens of Aulacomya atra and Mytilus chilensis from the fjord Comau to the lowest 0.1 mm using a vernier caliper. For this investigation mussels were sampled in the intertidal zone (M. chilensis) and the shallow subtidal zone (A. atra). The sampling depth ranged from 0 to 20 m below Mean Sea Level (MSL).This dataset was generated in the frame of the co-operation between the Huinay Scientific Field Station (http://www.huinay.cl) and the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (http://www.awi.de).