Identification of the geographical origins of Manila clam (Ruditapes philippinarum) by Multi-element stable Isotope Analysis

Abstract

Globalization of seafood and aquaculture products and their convenient marketing worldwide, increases the possibility for the distribution of mislabeled products; thereby underlining the need to identify their origin. The manila clam (Ruditapes philippinarum) is one of the most fished and farmed bivalves in the world. Multi-element isotopes analysis provides information about ecological and geographical origin of seafood and aquaculture products. In this investigation, we measured carbon, nitrogen, sulfur stable isotopes (δ13C, δ15N, δ34S) and strontium, neodymium isotope (87Sr/86Sr, 143Nd/144Nd) of the manila clam (Ruditapes philippinarum) originating from three countries (Korea, North Korea, China). Linear Discriminate Analysis (LDA) was applied to discriminate between manila clam of different geographical origin. δ13C, δ15N, δ34S, 87Sr/86Sr and 143Nd/144Nd values for the 255 samples (NKorea = 125, NN.Korea = 50, NChina = 50) from the three countries were measured. The range of δ13C values of all samples is -18.22 ~ - 16.31‰, δ15N values is 8.53 ~ 10.26‰, δ34S values is 16.03 ~ 18.54‰, 87Sr/86Sr values is 0.70924 ~ 0.70941, 143Nd/144Nd values is 0.511748 ~ 0.512151. The dual plotting of the stable isotope did not completely identify the origin. In particular, the results of China and North Korea overlapped. When applying LDA, the distribution of carbon, nitrogen, and sulfur shows a similar tendency between North Korea and China, which is a factor that lowers the credibility of the identification of origin. However, adding neodymium and strontium isotope analysis results to the LDA analysis shows that the discrimination of origin is improved. This suggests that multi-isotope analysis and LDA analysis could be reliable tools to identify the origin of manila clam.