Fish ages generated from counting growth rings of otoliths can be validated by measuring the ratio of lead (Pb-210) to radium (Ra-226) in the otolith core. Lead and radium are naturally occurring elements that become incorporated into the otolith structure. Over time the radium naturally decays to lead at a predicable rate, so the ratio of lead to radium trapped in the calcified structure of the otolith can provide an estimate of fish age. The AFSC Age and Growth Program has the capability to accurately measure lead and radium and has used this technique to validate ages from northern rockfish, Pacific ocean perch, rougheye rockfish, sablefish, shortraker rockfish, shortspine thornyhead, and walleye pollock.
- Kastelle, C.R., D.K. Kimura, A.E. Nevissi, and D.R. Gunderson. (1994) Using Pb-210/Ra-226 disequilibria for sablefish (Anoplopoma fimbria) age validation. Fish. Bull. 92:292-301.
- Kimura, D.K., and C.R. Kastelle. (1995) Perspectives on the relationship between otolith growth and the conversion of isotope activity ratios to fish ages. Can. J. Fish. Aquat. Sci. 52: 2296-2303.
- Kastelle, C.R., D.K. Kimura, S.R. Jay. (2000). Using Pb-210/Ra-226 disequilibrium to validate conventional ages in Scorpaenids (genera Sebastes and Sebastolobus). In 2nd International Symposium on fish Otolith Research & Application, Bergen, Norway, 20-25 June 1998. Fish. Res. 46:299-312.
- Kastelle, C.R., and J.E. Forsberg. 2002. Testing for loss of Rn-222 from Pacific halibut (Hippoglossus stenolepis) otoliths. Fish. Res. 57:93-98.
- Kastelle, C.R., K.E.W. Shelden, and D.K. Kimura. 2003. Age determination of mysticete whales using Pb-210/Ra-226 disequilibria. Can. J. Zool. 81:21-32.
- KASTELLE, C. R., and D. K. KIMURA. 2006. Age validation of walleye pollock (Theragra chalcogramma) from the Gulf of Alaska using the disequilibrium of Pb-210 and Ra-226. ICES J. Mar. Sci. 63:1520-1529.
- HUTCHINSON, C. E., C. R. KASTELLE, D. K. KIMURA, and D. R. GUNDERSON. 2007. Using radiometric ages to develop conventional ageing methods for shortraker rockfish (Sebastes borealis), p. 237-249. In J. Heifetz, J. DiCosimo, A. J. Gharrett, M. S. Love, V. M. O'Connell, and R. D. Stanley (editors), Biology, Assessment, and Management of North Pacific Rockfishes. University of Alaska Sea Grant Program Report No. AK-SG-07-01, University of Alaska, Fairbanks.