Radiometric age determination of the Atlantic sturgeon, (Acipenser oxyrinchus): A feasibility study using pectoral fin rays

Investigators: Allen H. Andrews, Erica J. Burton, Kenneth H. Coale, and Gregor M. Cailliet

The longevity of the Atlantic sturgeon is estimated at greater than 40 years based on microstructural annulus interpretation of pectoral fin rays. To validate this estimate, an attempt was made to measure the disequilibria of ²¹⁰Pb and ²²⁶Ra in pectoral fin rays to determine radiometric age. Evidence suggests that two of the assumptions for radiometric age determination were violated. First, exogenous ²¹⁰Pb is incorporated into the fin ray at levels that greatly exceed ingrowth from ²²⁶Ra. Second, vascularization, whether it is temporary or persistent with age, may allow migration of nuclides throughout the fin ray, violating the need for a closed system. Because ²²⁶Ra levels were fairly consistent, it appears that exogenous ²¹⁰Pb contributed most to the violation of radiometric ageing assumptions. Deviation in ²¹⁰Pb levels from those expected due to ingrowth alone was inconsistent and could not be predicted. Radiometric ageing assumption would have probably been met had otoliths been used. However, because otoliths are small and irregular, fish are rare, and there is a moratorium on harvesting, a similar study using otoliths was not possible.