Laidig et al : Age and growth of Sebastes mystinus 



803 



3.00 mm, and the average observed diameter of 

 the third zone was 3.67 mm (Fig. 4). 



Growth 



Growth between the sexes was significantly 

 different (P<0.05); females grew faster and 

 reached a larger maximum size than did males 

 (Fig. 5). The von Bertalanffy growth model 

 parameters for females were t^ = -1.34 years, 

 k = 0.149/year, and L„ = 400.16 mm FL and for 

 males were t^ - -0.95 years, /;■ = 0. 195/year, and 

 L„ = 329.41 mm FL. 



Growth models for both sexes were not 

 significantly different (P>0.05) between 

 the southern CPFV and northern speared 

 samples (Fig. 6). The models representing 

 males were virtually identical, with param- 

 eters for the CPFV model of t^ = -0.94 years, 

 k = 0. 195/year, and L„ = 331.66 mm FL, and 

 for the speared model of t^ = -0.99 years, 

 k = 0.194/year, and L^ = 323.14 mm FL. There 

 was no significant difference between females; 

 <„ = -1.94 years, k = 0.107/year, and L„ = 430.74 

 mm FL for the CPFV samples and t^ = -1.14 

 years, k = 0.166/year and L„ = 393.34 mm FL 

 for the speared. Females from CPFV were 

 larger at ages after 15 years than those that 

 had been speared. 



Discussion 



100 200 300 400 500 



Julian date of capture (day) 



600 



700 



Figure 2 



Growth of blue rockfish (Sebastes mystinus) collected nearshore during 

 their first 1.5 years. Solid line is the fitted linear growth model l/i=99; 

 r-=0.91). Vertical line represents 1 May, one year after the parturition 

 date of 1 January (i.e. 365 +120=485 days). 



We estimated the age (using the break-and- 

 burn technique) of blue rockfish to be greater 

 than that reported in earlier studies. Aging the 

 scales of blue rockfish. Miller and Geibel ( 1973 ) 

 reported maximum ages of 24 and 17 years for 

 females and males, respectively, whereas the 

 oldest of either sex reported by MacGregor 

 (1983) was only 13 years. Based on modal pro- 

 gression of length distributions, the estimate of 

 the oldest individuals of either sex calculated 

 by Karpov et al. (1995) was 17 years. In a study 

 of blue rockfish off Newport, Oregon, McClure 

 (1982) examined otolith surfaces and deter- 

 mined that the oldest female was 16 years, 

 and the oldest male was only 12 years. In aging 

 males to 44 years and females to 41 years, our 

 study more than doubled the recorded maxi- 

 mum ages for blue rockfish, demonstrating the 

 value of the break-and-burn section method for 

 accurate age determination. 



Age data were validated by using an edge analysis and 

 the first translucent zone was validated as corresponding 

 to the first annual growth increment. Campana (2001) 

 pointed out that there are problems in using edge analysis 

 as a validation tool. Specifically the extension of younger, 

 validated ages to older, nonvalidated ages. In our study, 

 we validated ages up to 23 years for females and up to 25 



30 



2.5 



2.0 



g 1 5 



05 



0,0 



Diameter = 0.02(FL) - 0.02 



60 

 Fork length (mm) 



120 



Figure 3 



Change in otolith diameter with fish length for young-of-the-year and 

 one-year-old blue rockfish (Sebastes mystinus). Solid line is the fitted 

 linear model ( n = 198; r2=0.95 ). Dashed line represents an estimated total 

 otolith diameter of 2.19 mm for a fish of 108.5 mm FL (i.e. fish length at 

 time of translucent zone completion). 



years for males; ages of older fish could not be positively 

 validated. Therefore, caution must be taken when using 

 the older ages. 



The growth rates of blue rockfish in our study were 

 similar to those estimated by others in California, but 

 slower than conspecifics off Oregon (Fig. 7). MacGregor 

 (1983) examined blue rockfish from southern California 

 and determined the combined male and female growth 



