102 



Fishery Bulletin 103(1) 



200 



150 



100 



~ 50 



O 



< 



-50 



-100 



-150 



° Quillback rockfish (n=15) 

 ^^— Exponential Rise 

 - - - Mean prebomb value (-907 %o) 

 Two sigma value (-67.7 %„) 



* 



^ 



1930 



1940 



1950 



1 960 1 970 



Birth year 



1980 



1990 



2000 



Figure 2 



Radiocarbon (4 14 C) values for quillback rockfish iSebastes maliger) otolith cores 

 (n = 15) in relation to estimated birth year. Horizontal error bars represent the 

 age estimate uncertainty from growth zone counts (CV=2.6%, year rounded 

 to the nearest whole number) and vertical error bars represent the 1-aAMS 

 (accelerator mass spectometry) analytical uncertainty. The solid line represents 

 the exponential curve fitted to the data that was used to determine the year of 

 initial rise in 14 C levels from prebomb levels (the fitted function had the form 

 Y=A+B exp(CX) with Y = 14 C, X=birth year, and A, B, and C as fitted param- 

 eters). The dashed line represents the +2 SD level (-67.7%r) associated with the 

 average prebomb 14 C value (-90.7 ±11.5 r /rr ; dotted line); the intersection of the +2 

 SD line and the curve was used to define the year-of-initial-rise in 14 C values. 



this sample was the first to have a 14 C value (-66.9 

 [±3.3]%e) that was above prebomb radiocarbon levels 

 with a +2 SD criteria (upper limit of-67.7%r). This first 

 indication of a rise in 14 C related to the rise of the bomb 

 was in agreement with the exponential fit of the quill- 

 back rockfish 14 C times series (Fig. 2). The 14 C record 

 for quillback rockfish otoliths peaked in 1967 with a 

 maximum 14 C concentration of +105.4 (±4)%e. This peak 

 was followed by a generally declining, but inconsistent, 

 trend in 14 C values to 1985 (last birth year sampled). 



The 14 C values measured in quillback rockfish oto- 

 liths plotted against estimated birth years produced 

 a characteristic increasing and decreasing curve rep- 

 resentative of bomb-generated 14 C changes over time 

 (Fig. 3). The quillback rockfish 14 C record was syn- 

 chronous with a 14 C time series for southeast Alaskan 

 waters determined from yelloweye rockfish otoliths 

 (Kerr et al., 2004); the average prebomb 14 C values for 

 the quillback rockfish were in close agreement with 

 the average yelloweye rockfish prebomb levels (-102.2 

 [±9.3]%c [mean ±SD]). The year of initial rise in the 

 quillback and yelloweye rockfish records (1959 [±1 year] 

 cf. 1958 [±2 years]) and peak in 14 C values (1967 cf. 

 1966) for these two species coincided within one year, a 

 period encompassed within the uncertainty associated 



with break-and-burn age estimates. Furthermore, the 

 postbomb decline in quillback rockfish 14 C values was 

 similar to that of the yelloweye rockfish. In addition, 

 thirteen of the fifteen quillback rockfish 14 C values fell 

 within the confidence intervals of the yelloweye rockfish 

 14 C curve (Fig. 3). 



The comparison of the quillback rockfish 14 C record 

 with that for Hawaiian Islands corals (Toggweiler et al., 

 1991; Druffel et al., 2001) and two otolith-based north- 

 ern hemisphere 14 C chronologies (northwest Atlantic 

 haddock [Campana, 1997] and Barents Sea Arcto-Nor- 

 wegian cod [Kalish et al., 2001]) revealed similarities in 

 the year of initial rise and rate of rise of 14 C values, and 

 differences in the pre- and postbomb eras that can be 

 explained by regional oceanographic effects (Fig. 4). 



Discussion 



Sample size assessment 



Although the 14 C technique has great potential for vali- 

 dating the age of many long-lived fishes, one of the 

 main disadvantages has been the high cost of AMS 

 14 C analyses. By providing a means of defining the 



