97 



Abstract — Rockfishes {Sebastes spp. i 

 support one of the most economically 

 important fisheries of the Pacific 

 Northwest and it is essential for sus- 

 tainable management that age esti- 

 mation procedures be validated for 

 these species. Atmospheric testing 

 of thermonuclear devices during the 

 1950s and 1960s created a global 

 radiocarbon ( 14 C) signal in the ocean 

 environment that scientists have iden- 

 tified as a useful tracer and chrono- 

 logical marker in natural systems. 

 In this study, we first demonstrated 

 that fewer samples are necessary for 

 age validation using the bomb-gener- 

 ated 14 C signal by emphasizing the 

 utility of the time-specific marker- 

 created by the initial rise of bomb- 

 14 C. Second, the bomb-generated 14 C 

 signal retained in fish otoliths was 

 used to validate the age and age 

 estimation method of the quillback 

 rockfish iSebastes maliger) in the 

 waters of southeast Alaska. Radio- 

 carbon values from the first year's 

 growth of quillback rockfish otoliths 

 were plotted against estimated birth 

 year to produce a 14 C time series 

 spanning 1950 to 1985. The initial 

 rise in bomb- 14 C from prebomb levels 

 (- -90%e) occurred in 1959 [±1 year] 

 and 14 C levels rose relatively rapidly 

 to peak A U C values in 1967 (+105.4<2c) 

 and subsequently declined through 

 the end of the time series in 1985 

 (+15.4% ). The agreement between the 

 year of initial rise of 14 C levels from 

 the quillback rockfish time series 

 and the chronology determined for 

 the waters of southeast Alaska from 

 yelloweye rockfish (S. ruberrimus) 

 otoliths validated the aging method 

 for the quillback rockfish. The concor- 

 dance of the entire quillback rockfish 

 14 C time series with the yelloweye 

 rockfish time series demonstrated 

 the effectiveness of this age valida- 

 tion technique, confirmed the longev- 

 ity of the quillback rockfish up to a 

 minimum of 43 years, and strongly 

 confirms higher age estimates of up 

 to 90 years. 



Age validation of quillback rockfish 

 (Sebastes maliger) using bomb radiocarbon 



Lisa A. Kerr 



Allen H. Andrews 



Moss Landing Marine Laboratories 



California State University 



8272 Moss Landing Road 



Moss Landing. California 95039 



Present address (for L A, Kerr) Chesapeake Biological Laboratory 



University of Maryland Center 

 for Environmental Science 



P.O. Box 38. 



Solomons. Maryland 20688 

 E-mail address (for L A Kerr, contact author): kerng>cbl umcesedu 



Kristen Munk 



Alaska Department of Fish and Game 

 Division of Commercial Fisheries 

 1255 W. 8th Street 

 Juneau, Alaska 99801 



Kenneth H. Coale 



Moss Landing Marine Laboratories 

 California State University 

 8272 Moss Landing Road 

 Moss Landing, California 95039 



Brian R. Frantz 



Center for Accelerator Mass Spectrometry 

 Lawrence Livermore National Laboratory 

 7000 East Avenue 

 Livermore, California 94551 



Gregor M. Cailliet 



Moss Landing Marine Laboratories 

 California State University 

 8272 Moss Landing Road 

 Moss Landing, California 95039 



Thomas A. Brown 



Center for Accelerator Mass Spectometry 

 Lawrence Livermore National Laboratory 

 7000 East Avenue 

 Livermore, California 94551 



Manuscript submitted 11 April 2003 

 to the Scientific Editor's Office. 



Manuscript approved for publication 

 24 August 2004 by the Scientific Editor. 



Fish. Bull. 103:97-107 (2005). 



Rockfishes {Sebastes spp.) comprise 

 one of the most commercially impor- 

 tant fisheries in the northeast Pacific 

 Ocean. Some rockfish species possess 

 life history characteristics, such as 

 long life, slow growth, late age at 

 maturity, low natural mortality, and 

 variable juvenile recruitment success, 

 all of which make them particularly 

 vulnerable to overfishing (Adams, 

 1980; Archibald et al., 1981; Leaman 

 and Beamish, 1984; Cailliet et al., 

 2001.1. Rockfish population biomass 

 and size composition have declined 

 to very low levels today in part 

 because of continued high exploita- 

 tion rates (Love et al., 2002). Preven- 

 tion of further population declines is 

 a management imperative. Sustain- 



able management of marine fisheries 

 requires accurate life history infor- 

 mation, of which validated age and 

 growth characteristics can be one of 

 the most important aspects. 



Underestimated age can lead to 

 inflated estimates of total allow- 

 able catch for a fishery that is un- 

 sustainable at that level of exploita- 

 tion (Beamish and McFarlane, 1983; 

 Campana, 2001). For example, un- 

 derestimated longevity and improper 

 management allowed overfishing that 

 accelerated the decline of the Pacific 

 ocean perch (Sebastes alutus) of the 

 northeastern Pacific Ocean (Beamish, 

 1979; Archibald et al., 1983). Reliable 

 estimates of age are also essential 

 for understanding life history traits, 



