Using enriched stable isotopes of barium and magnesium to batch mark otoliths of larval golden perch (Macquaria ambigua, Richardson)

Enriched stable isotope immersion techniques were used to mark the otoliths of larval golden perch (Macquaria ambigua) immediately post-hatch. Two experiments were undertaken: the first involved rearing larvae in water enriched with three concentrations of 137Ba for 1–5 days. Marks were produced in as little as 1 day; however, otolith isotope ratios reached equilibrium with the water in 5 days at 90 μg·l−1. The second experiment involved rearing larvae in isotope enriched water with combinations of stable isotopes of Ba and Mg for 4 days after hatching. Seven significantly different isotopic signatures were produced using three Ba isotopes, which were reflective of the water. Only slight differences were found in otoliths of larvae that were reared in combinations of Mg isotopes, which did not reflect the water chemistry. The length of golden perch at 3 weeks of age showed that isotope immersion did not negatively affect early growth.