LAUSR

The conservation of land-locked populations of migratory fishes is increasingly important in the era of dam removal and habitat reconnection. We used an otolith strontium (Sr) tracer (87Sr/86Sr) to test the hypothesis that a land-locked population of an endangered salmonine species, Sakhalin taimen (Parahucho perryi), retains the capacity for anadromy, and that some individuals out-migrate from the reservoir to the sea. Years later, these individuals return but are blocked by the migration barrier of the reservoir dam and are denied reproduction in their natal streams. Juvenile taimen collected from the reservoir and two nearby regions were classified based on their otolith Sr isotopic signatures to their regions of origin with an overall accuracy of 88%. When the same classifier was applied to ocean-caught adult taimen, we predicted some individuals had originated from the reservoir with high posterior probabilities (> 0.9). Whether the land-locked Sakhalin taimen can help sustain the metapopulation dynamics of the species at the watershed scale may depend on whether, and how soon, the disrupted migration pathway is restored.