Effects on Ca2+ concentrations in seawater on element content of fish body and otolith of juvenile Paralichthys olivaceus

We investigated the effects of Ca2+ concentrations on element content of fish body and otolith of juvenile Paralichthys olivaceus that were raised at 20℃ in artificial seawater for 60 more days. Five groups of seawater with Ca2+ concentrations 200 mgL-1 (group A), 400 mgL-1 (group B, control), 800 mgL-1 (group C), 1 600 mgL-1 (group D), and 3 000 mgL-1 (group E), were used for raise. It was found that with the increase of Ca2+ concentration, the contents of P, Na, Mg, Sr, Fe, Mn and Ni in fish body decreased, and that Ca2+ concentrations significantly influenced the otolith length, width, L/W and weight. Specifically, otolith length and width of juvenile P.olivaceus group A were significantly lower than that of group B and C; L/W was significantly lower than that of group D; and otolith weight was significantly lower than that of group B and D. Sr content of otolith, significantly, and the ratio of Sr/Ca and Mg/Ca also decreased with increasing concentration of Ca2+. The results indicate that Ca2+ concentrations affect juvenile P.olivaceus significantly in terms of its body and otolith element content formation, composition and accumulation