Similarity of microchemical “fingerprints” between the pectoral fin ray and otolith of Coilia nasus

Abstract:

Otolith microchemistry are widely applied in the field of fish migration ecology. However, the extraction of otoliths always results in damage to tissue and the death of the fish. Therefore, it is of great importance to discover an alternative material as a nonlethal substitute for otoliths for effective microchemical “fingerprint” analysis. Consequently, the similarities of microchemical characteristics between the pectoral fin ray and otolith of Coilia nasus were compared in this study. The ratio of Sr/Ca and classification of Sr concentration mapping results in the otolith matched the typical patterns of anadromous, freshwater, and land-locked ecotypes well. Of note, the results of the pectoral fin rays showed that C. nasus taihuensis and C. brachygnathus had consistently low Sr/Ca ratios [(1.38±0.52)~ (2.04±0.74) and (1.40±0.32)~(1.81±0.66), respectively], which coincided with the first stage of C. nasus [(2.06±0.64)~(2.26±0.29), i.e., freshwater phase], which reflected the characteristics of the freshwater habitat “fingerprints.” Furthermore, the C. nasus pectoral fin ray, like the otolith, could be divided into three distinct phases from the core to the edge, corresponding to the bluish, greenish, and bluish “fingerprint” changes in the results of mapping analysis. The present study strongly suggested that pectoral fin rays are a nonlethal and low-damage substitute for otoliths to investigate the migratory habit and conduct life history research using microchemical “fingerprint” analysis. In addition, considering the advantages of sample collection and pre-treatment, pectoral fin rays could play a role in the future as an alternative material for accurate assessment of Coilia resources and the effectiveness of artificial fish release using microchemical marking approaches.