The harvestable fraction corresponding to the mean bill length of  the sandpipers, the dunlin Calidris alpina and the red knot Calidris canutus and composed of the accessible fraction of benthos (found in the top 4 cm of the mud core) and of ingestible sizes (not too large and not too small). Ingestible sizes are species specific, and depend on the shape of the mollusc. Sizes available for C. canutus and C. alpina species are reported in Philippe et al. (2016).