Salinities, not diets, affect strontium/calcium ratios in otoliths of Anguilla japonica |
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Authors: | Shih-Huan Lin Yoshiyuki Iizuka |
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Institution: | a Institute of Fisheries Science, College of Life Science, National Taiwan University, Taipei, Taiwan, ROC b Institute of Earth Sciences, Academia Sinica, Nankang, Taipei, Taiwan, ROC |
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Abstract: | Although otolith Strontium (Sr)/calcium (Ca) ratios have been widely used to reconstruct the past salinity environmental history of anguillid eels, factors affecting the Sr/Ca ratios in otoliths are incompletely understood. Japanese Eel (Anguilla japonica) elvers (mean length 54.7 ± 2.1 mm) were collected in the estuary during their upstream migration and reared at 5 different salinities (0, 5, 15, 25, and 35 psu) and 3 types of feeding conditions (formulated feed, tubifex, and starvation) for 30 days to evaluate the effects of salinity and diets on otolith Sr/Ca ratios. Ca and Sr concentrations in the ambient water significantly increased with salinity (SAL) as Ca] water = 15.50SAL − 5.56, and Sr] water = 0.21SAL + 0.03, respectively. Sr/Ca ratios in otoliths increased with salinity (SAL) of the rearing water as (Sr/Ca) × 1000] otolith = 0.091SAL + 3.790. In diets, Sr/Ca ratios were 4 times higher in tubifex than in formulated feed. However, in otoliths, ANOVA indicated that Sr/Ca ratios did not differ significantly between groups fed on tubifex or formulated feed (p = 0.118). Otolith Sr/Ca ratios were negatively correlated with fish growth rates while the growth rates differed significantly among rearing conditions with different salinities and diets. Partition coefficients of the Sr/Ca ratios from ambient water to fish tissues and otoliths significantly increased with salinity. The Sr/Ca ratios of Japanese Eel otoliths thus were positively correlated with the ambient salinity and decreased with increasing fish growth rate, but was not affected by fish diet. |
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Keywords: | Anguilla japonica Diets Growth rate Otolith Partition coefficients Sr/Ca ratios |
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