Salinities, not diets, affect strontium/calcium ratios in otoliths of Anguilla japonica

• Published in: Journal of experimental marine biology and ecology 2007-03, Vol.341 (2), p.254-263
• Main Authors: Lin, Shih-Huan, Chang, Chih-Wei, Iizuka, Yoshiyuki, Tzeng, Wann-Nian
• Format: Article
• Language: English
• Subjects: Agnatha. Pisces; Anguilla japonica; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Brackish; Diets; Freshwater; Fundamental and applied biological sciences. Psychology; Growth rate; Marine; Otolith; Partition coefficients; Sea water ecosystems; Sr/Ca ratios; Synecology; Tubifex; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution
• ISSN: 0022-0981; 1879-1697
• DOI: 10.1016/j.jembe.2006.10.025

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.