Time lag of the response on the otolith strontium/calcium ratios of the Japanese eel, Anguilla japonica to changes in strontium/calcium ratios of ambient water

We conducted a laboratory experiment to validate the relationship between the otolith strontium/calcium (Sr/Ca) ratio of Japanese eels (Anguilla japonica) and water Sr/Ca ratio when the ratio in water was changed. A linear and additive mixed modeling approach was used to assess otolith Sr/Ca ratio for elver-juvenile Japanese eels when ambient water was changed from seawater to freshwater. There was a significant difference between otolith Sr/Ca ratios of eels reared in freshwater and in seawater (freshwater: 1.3-2.3; seawater: 7.0-7.8 mmol/mol). The response of otolith Sr/Ca ratios of eels was not detected until after 10 d and models suggested that it might not be completed until at least 30-60 d. This study indicated the detailed ability of otolith Sr/Ca ratio to be used as a proxy for reconstructing the individual environmental history of Japanese eels. These findings can provide some assurances for future otolith Sr/Ca studies of eels in this system or in other areas that have similar environmental conditions.