Exploring the use of radiotelemetry and lifetime otolith 87Sr/86Sr signatures to infer habitat use by dorado Salminus brasiliensis in the La Plata River basin.

Radiotelemetry and otolith chemistry are complementary methods for studying fish movement. 87Sr/86Sr signatures of two radio-tagged dorado Salminus brasiliensis revealed long-term presence in the Uruguay River and exposure to lower radiogenic waters potentially associated with the upper basin. Radiotelemetry data showed how variation in water 87Sr/86Sr can generate variation in otolith signatures without fish movement. Results suggest origins in the upper Uruguay River basin, and no evidence for migration to the Paraná River. These observations demonstrate the potential for integrative approaches to studying lifetime fish movement in South American rivers.