Abstract
Methods for confirming the accuracy of age determination methods are reasonably well established in fishes, but the millions of routine age determinations which take place every year require their own quality control protocols. In contrast, methods for ensuring accuracy in age determination of monodontids and other marine mammals are still being developed. Here we review the basis and application of bomb radiocarbon to marine mammal age validation, highlighting its value for providing unambiguous estimates of age for belugas and other long-lived animals which form growth bands. Bomb radiocarbon is particularly useful for marine mammals, given that the age of an individual animal can be determined to within ±1-3 years, as long as it was alive during the 1960s. However, ongoing age determinations require careful monitoring to ensure that age interpretations remain consistent across ages and through time. Quality control protocols using reference collections of ageing material, in conjunction with age bias plots and measures of precision, are capable of detecting virtually all of the systematic ageing errors that often occur once age determinations of an animal become routine.
Highlights
Age information forms the basis for calculations of growth rate, mortality rate, and productivity, ranking it among the most influential of biological variables
We describe the use of bomb radiocarbon as a powerful tool for validating the age of wild, long-lived marine mammals, including belugas
Bomb radiocarbon derived from atmospheric nuclear testing provides one of the best age validation approaches available for virtually any long-lived organism that forms growth bands, whether it be in trees (Worbes and Junk 1989), fish (Campana 1997), sharks (Francis et al 2007), bivalves (Weidman and Jones 1993), corals (Druffel and Linick 1978), humans (Spalding et al 2005) or marine mammals (Tauber 1979, Bada et al 1987, Stewart et al 2006)
Summary
Age information forms the basis for calculations of growth rate, mortality rate, and productivity, ranking it among the most influential of biological variables. Calculations as simple as growth rate, or as complex as virtual population analysis, all require age data, since any rate calculation requires an age or elapsed time term. In the case of fishes, ages are usually estimated using counts of annual growth increments found in otoliths, scales, fin rays, spines, vertebrae and bones (Campana 2001). Scales, and fin rays, requiring the preparation of a tooth, bone or ear plug for direct age determination. Age determination in marine mammals is often more challenging than it is in teleosts, in part because of the absence of otoliths in the former, and in part because the number of teleosts that are aged annually is thousands of times larger than is the case for marine mammals (Campana and Thorrold 2001).
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