Comparative study on otolith Sr∶Ca ratios of Neosalanx taihuensis from Taihu Lake and Hongze Lake of China

Abstract:

An electron probe microanalyzer was used to analyze the microchemistry of Sr and Ca in sagittal otoliths of the Salangid icefish Neosalanx taihuensis from southern (area of Baiquexiang) and northern (area between Wutangmen and Wuguishan) Taihu Lake, and Hongze Lake (area of Laozishan). The results of both the life history transect analysis and X ray intensity mapping analyses clearly showed that there were two different patterns in otolith samples of N. taihuensis from northern Taihu Lake. One was characterized by high Sr∶Ca ratios (Sr∶Ca×1000) with a mean value of 21.41 SD, 0.50; N=4); whereas another showed low Sr∶Ca ratios with a mean value of 1.64 (SD, 0.12; N=5). In contrast, mean otolith Sr∶Ca ratios of the fish from southern Taihu Lake was 3.12 (SD, 0.07; N=10). That of N. taihuensis form Hongze Lake was 5.42 (SD, 0.32; N=9). The difference of otolith Sr∶Ca ratio values was statistically significant at a 5% level among the icefish from different water areas. In addition, the X ray intensity maps showed that the otolithes of N. taihuensis from Hongze Lake presented high Sr concentric rings, while Sr distribution in those of the icefish from Taihu Lake were almost homogeneous. The results of the present study indicated that different microchemistry patterns of otolith existed not only between the icefishes from the Taihu Lake and Hongze Lake, but also existed between the icefishes from different water areas of Taihu Lake, suggesting a possibility to separate different geographic resources of N. taihuensis by means of the different features of otolith microchemistry.