Through long periods of time, it would not be surprising to see significant changes in the compositions of communities and in their constituent species. In this study, two assemblages that are not separated by a large interval of time also exhibit significant changes in their community structure and in the shape of one species. The scallop, “Pecten” thompsoni, was studied through a technique called landmark morphometrics where the shape of the shell can be compared quantitatively independently of size. In these two populations, shell shape differs especially in the area of the byssal notch. More surprisingly, the two populations also show differences in growth patterns so that in one population, the scallops do not change shape as they increase in size but in the second population, the shape changes once they grow to a certain size (and/or age). These changes may be related to environmental differences (such as water energy) between the two samples.