Regulation of calcium and strontium deposition on the otoliths of juvenile tilapia, Oreochromis niloticus

Radioisotopes of calcium and strontium were used to test for a relationship between the environmental concentrations of each element and their respective deposition races on the otolith. On the basis of Ca-45 and Sr-89 assays, the rate of strontium deposition on the otolith was influenced by strontium concentrations in the water, while the rate of calcium deposition was affected neither by food nor water calcium concentrations. Thus, the deposition rate of strontium on the otolith at least partially reflects environmental availability, while that of calcium does not. Sources in the water contributed 75% of calcium and 88% of strontium to the sagittae of Nile tilapia, Oreochromis niloticus, with the remainder being provided by the diet.