Strontium isotope analysis of otoliths reveals differences in the habitat salinity among three sympatric stickleback species of the genus .

The analysis of otolith Sr isotope ratios (Sr/Sr) is a powerful method to study fish migration in freshwater areas. However, few studies have applied this method to study fish movement in brackish-water environments. Furthermore, despite the fact that habitat differentiation has been shown to drive genetic differentiation and reproductive isolation among stickleback fish, no studies have used the otolith Sr/Sr ratios to analyze habitat differentiation between stickleback ecotypes and species.