Radiocarbon from nuclear testing applied to age validation of black drum, Pogonias cromis

Radiocarbon (¹⁴C) in the world's oceans increased sharply between 1950 and 1970 as a result of the atmospheric testing of nuclear weapons. Through comparison with the ¹⁴C time series reconstructed from atmospheric measurements and marine carbonates, Kalish, in 1993, used the ¹⁴C concentration measured in fish otolith cores as a means of confirming the annulus-based age estimates for some South Pacific fish species. Here we report the pre- and postbomb ¹⁴C chronology of North Atlantic adult black drum (Pogonias cromis), assumed to be between 15 and 42 yr of age on the basis of otolith annulus counts. According to accelerator mass spectrometry (AMS) assays, ¹⁴C in otolith cores increased sharply between 1958 and 1964, with a timing and magnitude which was very similar to that of the atmospheric bomb ¹⁴C signal. The correspondence between the two ¹⁴C chronologies indicates that the annulus-based age assignments were accurate on average to within 1-3 yr. Differences between the black drum Δ¹⁴C chronology and that of other marine carbonates in the North Atlantic are explained by the estuarine habitat of young-of-the-year black drum and by the fact that estuarine Δ¹⁴C values more closely reflect atmospheric values than surface ocean values. At present, there is no other age-validation technique that can confirm the absolute age of long-lived fish species with comparable levels of accuracy.