Migration Patterns of Two Gizzard Shads, Clupanodon thrissa (L., 1758) and Nematalosa nasus (Bloch, 1795) (Clupeiformes: Clupeidae), from Vietnam as Revealed by Otolith Microchemistry Analyses.

Otoliths can be used to examine the migration history of fish individuals based on trace element concentrations in them. In order to verify migration patterns of Clupanodon thrissa and Nematalosa nasus (Clupeiformes: Clupeidae), Sr:Ca ratios in otoliths of 13 individuals (6 C. thrissa and 7 N. nasus) collected from Vietnam were examined. In addition, to provide guidelines for identification, the otolith morphology of the two species was comparatively illustrated. The otolith Sr:Ca ratios from the core to the edge ranged from 0 to 5.7 × 10-3 and 0 to 4.9 × 10-3 for C. thrissa and N. nasus, with an average of 1.8 × 10-3 and 2.3 × 10-3, respectively. The present data do not show typical anadromous profiles as the Sr:Ca ratio of the two species mostly fluctuates evenly from 0 to 4 × 10-3. These data suggest that the life cycles of the studied populations of C. thrissa and N. nasus are entirely completed in estuarine habitats. [ABSTRACT FROM AUTHOR]