Age validation of freshwater drum using bomb radiocarbon

Shannon L. Davis-Foust, Ronald M. Bruch, Steven E. Campana, Robert P. Olynyk, John Janssen

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23 Citations (Scopus)


The ages of freshwater drum Aplodinotus grunniens have typically been estimated by counting the growth increments on their scales or otoliths, but the accuracy of these estimates has not been validated. We used accelerator mass spectrometry (AMS) bomb radiocarbon dating to validate age estimates from sagittal otoliths of freshwater drum from the Lake Winnebago system, Wisconsin. The freshwater drum Δ14C chronology from the AMS assay closely reflects the timing and shape of other bomb radiocarbon chronologies, thus validating the accuracy of otolith growth increments to at least age 52 ± 2 years. The progression of a strong 1983 year-class, which was detected every year sampled over the course of the study (1986, 2003-2007), and indices of year-class abundance calculated from trawling assessments on Lake Winnebago (1986-2007) corroborated otolith ages. Age estimate comparisons between scales, anal spines, dorsal spines, and otoliths showed scales and spines to be completely unreliable as aging structures after age 2. Freshwater drum live to very old ages relative to most other Great Lakes fishes; our oldest specimen based on an otolith age estimate was 58 years old.

Original languageEnglish
Pages (from-to)385-396
Number of pages12
JournalTransactions of the American Fisheries Society
Issue number2
Publication statusPublished - 2009

Bibliographical note

Funding Information:
We thank the fisheries staff and the many volunteers of the Wisconsin Department of Natural Resources Upper Fox–Wolf Work Unit for collecting freshwater drum samples from the trawler RV Calumet each summer on Lake Winnebago and the local sheepshead (i.e., freshwater drum) tournament contestants for donating additional samples. Special thanks go to Seth Herbst for aging otoliths in the Wisconsin Department of Natural Resources Fish Age Estimation Laboratory, Oshkosh; to Jamie Joudrey for embedding and sectioning otoliths at the Bedford Institute of Oceanography, Dartmouth, Nova Scotia; and to Sturgeon for Tomorrow for supporting travel for Ron Bruch and Shannon Davis-Foust to work with Steven Campana for 3 d on the project at the Bedford Institute of Oceanography. This project was funded by the Wisconsin Department of Natural Resources Fish and Wildlife Segregated Fund, the Sport Fish Restoration Fund, and the Sturgeon Spearing License Fund.


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