Determination of Fish Age Using 210Pb: 226Ra Disequilibrium Methods

Previous workers have used disequilibrium in the 210Pb: 226Ra ratio in fish otoliths to estimate the age of four teleost species: Hoplostethus atlanticus, Macruronus novaezelandiae, Sebastes diploproa, and Sebastes mentella. We argue that uncontrollable errors due to degassing of intermediate 222Rn from otoliths, unknown sources and sinks of 210Pb and 226Ra, possible changes in the ratio with which these isotopes are accreted to the otolith over the life of the fish, contamination by 210Po, difficulties in obtaining otolith cores, and the dependence of the estimated radiometric ages on the mass growth-in-time model usually adopted for otoliths can invalidate the application of disequilibrium techniques to fish age estimation.