of a species throughout large areas may represent a
considerable logistic challenge, especially for those organisms displaying
cryptic habits and low densities. In such cases, sampling can only be
conducted by intensive trapping or time consuming inspection of
potential shelters. Particularly for crab species, an alternativemethod to
reconstruct the size structure of the population consists ofmeasuring the
width of the carapaces that have detached from the rest of the
exoskeleton and have been washed upon the shore or spread on the
sea bottom when crabs molted, and calculating size frequency
distributions (SFDs) based on these measurements (Stone, 1999).