Application of geometric methods to the morphological classification of five abalone species

Abalone is an economically important mollusc in the aquaculture industry; however, research on the morphological classification and geographical origin tracing of abalone species remains limited. In the present study, a total of 177 specimens were collected, comprising five abalone species - Haliotis madaka (T. Habe, 1977), Haliotis diversicolor Reeve, 1846, Haliotis gigantea Gmelin, 1791, Haliotis ovina Gmelin, 1791 and Haliotis discus hannai Ino, 1953 (including samples from wild and cultured populations in Liaoning Province, as well as a cultured population in Fujian Province). Generalised Procrustes Analysis (GPA) was applied to standardise the landmark data, thereby removing non-morphological sources of variation. Subsequently, multivariate statistical methods - including Principal Component Analysis (PCA) and Canonical Variate Analysis (CVA) were employed to quantify morphological differences. PCA results showed that PC1 and PC2 accounted for 62.23% and 12.68% of the total morphological variance amongst the five species, respectively, with a cumulative contribution of 74.91%. For the three H. discus hannai populations (Liaoning-wild, Liaoning-cultured and Fujian-cultured), PC1 and PC2 explained 50.57% and 12.07% of the total variance, respectively. CVA revealed that the first two canonical variates accounted for 69.59% of the overall shape variation amongst groups. These findings demonstrate that geometric morphometric approaches effectively distinguish amongst the five abalone species examined and successfully differentiate between wild and cultured specimens of H. discus hannai. However, the two cultured populations from Liaoning and Fujian Provinces exhibited considerable morphological overlap along the primary discriminant axis, precluding complete separation.