Investigation of surface topography differences in native and exotic invertebrates in the St. Lawrence River

The texture, or topography, interior of shells from native and exotic mollusks are measured and compared to determine if they can be discriminated. Area-scale fractal analysis is used to calculate relative areas as a function of scale, and the relative areas are used to evaluate the measurements. Measurements from a scanning laser profiler and from confocal and interferometric microscopes are compared, as are measurements of an original and a replica. The relative areas indicate clear differences between the measurement instruments. The largest relative areas are calculated from the confocal measurements. The trueness of the measurements has not been determined. However, the relative areas calculated from the confocal measurements are capable of discriminating the native clam from the exotic mussels with a confidence of greater than 99% at scales below 10 µm².