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| Photo: Alaska Fishery Science Center |
Rockfishes (Sebastes spp.) support one of the most economically important fisheries of the Pacific northwest. Because proper management strategies rely on growth rate, age structure, and longevity estimation, it is essential to validate the age estimation procedures and longevity for commercially important rockfish. Differential growth in length and thickness of fish otoliths, make age interpretations more subjective in long-lived species, such as rockfish. Atmospheric testing of thermonuclear devices during the 1950s and 1960s created a global radiocarbon (14C) signal in the ocean environment. The bomb-generated radiocarbon signal retained in fish otoliths can be used as a permanent, time-specific marker of the radiocarbon present in ambient seawater, making it a useful tool in age validation of fishes. The goal of this study was to determine radiocarbon levels in otoliths of the age-validated yelloweye rockfish (Sebastes ruberrimus) to establish a chronometer for radiocarbon in the waters of southeast Alaska and to validate age of the quillback rockfish (Sebastes maliger) using this chronometer. Radiocarbon values from the first year’s growth of 43 yelloweye rockfish otoliths were plotted against estimated birth year to produce a radiocarbon time series for southeast Alaskan waters from 1940 to 1990. Radiocarbon measured in quillback rockfish otoliths, with estimated birth years from 1950 to 1985, was similar to values recorded for the yelloweye rockfish during the same period. The agreement between the rockfish records successfully validated the age estimates for the quillback rockfish and the ageing methodology of otoliths for this species. The establishment of a radiocarbon chronometer in the waters of southeast Alaska, and the successful age validation of the quillback rockfish based on this chronometer provides a valuable tool useful for future age validation of marine fishes in this region.
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| Radiocarbon data (14C) from quillback rockfish otolith cores and the radiocarbon chronometer for the waters of southeast Alaska determined from yelloweye rockfish otolith cores |
Funding for this project has been provided in part by the University of California Sea Grant College Program, Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Pacific States Marine Fishery Council, Project AWARE, San Francisco State University Project Fund, Packard Foundation, and the Dr. Earl H. Myers and Ethel M. Myers Oceanographic and Marine Biology Trust.