STUDIES ON THE BEHAVIOR OF SOME TRACE-ELEMENTS IN BAY AREA .5. CHANGES IN CONCENTRATIONS OF TRACE-ELEMENTS IN ORGANS WITH GROWTH OF THE CULTURED YELLOWTAIL

The dependence of the concentrations of trace elements (Sn, Cu, Zn and Mn) in muscle and organs of cultured yellowtails on the body weight was examined during a 17 month period from May, 1980 to October, 1981. Four elements were analyzed by means of atomic absorption spectrophotometry after wet digestion with a mixture of nitric acid and hydrogen peroxide. The following results were obtained. (1) In the liver: the concentrations of copper and zinc increased gradually with the increase in body weight of up to 1500 g, whereas those of manganese were invariable. (2) In the muscle: the concentrations of copper, zinc and manganese were invariable. (3) In the kidney: the concentration of zinc increased markedly with the increase in body weight about 2000 g, and reached 61.8 mu-g/g for a body weight of 2800 g. (4) In the pyrolus: the concentrations of copper, zinc and manganese decreased with increase in body weight about 500 g, and were constant for body weights of up to 1000 g. (5) In the blood: the concentrations of copper, zinc and manganese were invariable. (6) The concentration of tin in every organs was lower than 1.0 mu-g/g. From results obtained, it was suggested that zinc played an important part of the birth of yellowtail and the kidney was controlling the changes in concentration of elements in the organs with the growth of yellowtail.