Fig 1.
Sampling sites along the Mekong River.
(A) Map of sampling sites for water (black circle) and fish (catfish) along the Mekong River, and (B) detailed map of the sites in the Mekong Delta.
Table 1.
Water samples collected along the Mekong River and its delta.
Fig 2.
Relationship between 87Sr/86Sr determined by the two laboratories (AETE-ISO OREME and IES).
Linear regression between the 87Sr/86Sr in water samples reported by IES (Taiwan) versus those reported by SARM (France). Black circles indicate sites along the Mekong mainstream, grey triangles indicate sites on tributaries and distributaries.
Table 2.
87Sr/86Sr and Sr concentrations.
Fig 3.
Water 87Sr/86Sr versus salinity along the Mekong River.
Water 87Sr/86Sr versus salinity along the Mekong mainstream (dark circles) and tributaries / distributaries (grey triangles); (A) for all sampling locations, and (B) only in saline waters (Mekong Delta) with a logarithmic regression. Labels at each point refer to the sampling sites in Fig 1 and Table 1.
Fig 4.
Water 87Sr/86Sr ratio versus distance from the sea along the Mekong River.
Water 87Sr/86Sr versus distance from the sea along the Mekong mainstream. Distances were estimated using Google Earth Pro. Labels at each point refer to the sampling sites in Fig 1 and Table 1.
Fig 5.
Water 87Sr/86Sr versus 1/Sr along the Mekong River; (A) with and (B) without tributaries and distributaries. Labels at each point refer to the sampling sites in Fig 1 and Table 1. Black circles indicate sites on the Mekong mainstream, grey triangles indicate sites belonging on tributaries and distributaries.
Table 3.
Trace element concentrations measured by the two laboratories (AETE-ISO OREME and IES).
Fig 6.
Ba/Ca ratios versus Sr/Ca ratios in the Mekong mainstream and tributaries.
Labels at each point refer to the sampling sites in Fig 1 and Table 1. Black letters correspond to sites on the Mekong mainstream, red letters to sites on tributaries, and blue letters to sites on distributaries.
Fig 7.
Main patterns of 87Sr/86Sr profiles in the otoliths of P. krempfi caught in the Mekong Delta.
(A) Dendrogram of the hierarchical cluster analysis on the right. (B, C and D) on the left, three main types of 87Sr/86Sr profiles from the core to the edge of the otolith coming from the three branches of the dendrogram. Vertical dotted lines mark the end of each year based on the position of the annual growth increments. Horizontal lines correspond to the mean water 87Sr/86Sr at each sampling location in the Mekong River, except for sampling locations in the Sekong River and Tonle Sap Lake that had higher and lower values, respectively. Labels on the point on each horizontal line refer to the sampling sites (Fig 1 and Table 1). Black dots indicate Mekong mainstream sites; grey triangles indicate a tributary or distributary.
Fig 8.
Comparison of 87Sr/86Sr profiles and Sr/Ca profiles for the same individuals.
Comparisons of 87Sr/86Sr profiles (solid line) and Sr/Ca profiles (dotted line) for four P. krempfi individuals. Profiles are shown from the core to the edge of the transverse otolith section. Vertical dotted lines mark the end of each year based on the position of the annual growth increments.
Fig 9.
Map of 87Sr/86Sr values along the Mekong River and tributaries.
Detailed values are listed in Table 2.