Otolith microstructure of an amphidromous goby (DOS02416-7, panel a and c) and a landlocked goby (DOS03534-19, panel b and d). Panel c and d illustrate the clear growth increments during the pelagic larval duration of the goby. The white arrows in panel a and b indicate the transect of otolith Sr:Ca ratio analysis. The black arrows indicate the otolith check mark where otolith Sr:Ca ratios drop from marine to freshwater signatures (panel a) and structural transition from clear concentric ring to ambiguous rings (panel b), respectively. Scale bars: 500 μm for panel a, b; 100 μm for panel c, d.”