Life history scan using otolith Sr：Ca ratios of diadromous fish in the Gouno River, western Japan.

Abstract

Otolith Sr：Ca ratios of eleven diadromous species in the Gouno River were analyzed to reconstruct their migratory histories. Tridentiger obscurus from the river estuary migrated only brackish water throughout life history. Amphidromous life mode for T. brevispinis, Rhinogobius nagoyae, R. fluviatilise, R. giurinus, Gymnogobius opperiens, G. urotaenia, Cottus kazika and Cottus sp. （middle-egg type） from the middle-reaches （down stream of Hamahara Dam） was supported by the ontogenetic changes in the Sr：Ca ratios. G. urotaenia and T. brevispinis from upper stream of Hamahara Dam were categorized as non-diadromous life mode by the constantly low Sr：Ca ratios. Also, non-diadromous life mode was found at Rhinogobius sp. OR （Sinjiko type） from downstream of Hamahara Dam. Intraspecific variation in the migration pattern recorded for G. urotaenia, T. brevispinis and Rhinogobius sp. OR （Sinjiko type） suggest a plasticity strategy for diadromous behaviors.