802 



Fishery Bulletin 101(4) 



Growth 



A von Bertalanflfy growth curve was fitted to the 

 fish length and age data. The form of the equa- 

 tion was 



^„(1 



, -kU - t„) 



■„)), 



where L, = fish length (mm FL) at age t; 



L„ = maximum fish length (mm FL), 

 k = growth completion rate (per year); 

 t = age (years); and 



Iq = theoretical age (years) when the fish 

 was length zero. 



Parameters for the growth curve were calculated 

 iteratively by using the method described by 

 Schnute (1981). Growth models were developed 

 separately for males and females to account for 

 possible sex-specific growth rates (Echeverria, 

 1986). Growth curves were fitted for the entire 

 sampling area and separately for the northern 

 and southern areas to examine potential latitu- 

 dinal trends in growth and by mode of collection. 

 Growth curves were compared by using the extra sum of 

 squares principle (Draper and Smith, 1981; Ratkowsky, 

 1983; Pearson and Hightower, 1991). 



Results 



A total of 1980 blue rockfish were examined; 655 of these 

 fish were caught by hook-and-line from CPFV, 133 pelagic 

 juveniles were collected in midwater trawls offshore, and 

 1245 fish were speared. Maximum size of fish from the 

 CPFVs was 365 mm FL for males and 444 mm FL for 

 females. Maximum size of speared fishes was 360 mm 

 FL for males and 412 mm FL for females. The oldest fish 

 from the CPFVs were a 44-year-old male and a 40-year-old 

 female, and the oldest speared fish were a 39-year-old male 

 and a 41-year-old female. There was a 5.6% APE between 

 readers. When ages were not in agreement, the readers 

 would discuss the differences and if no consensus could be 

 reached, the suspect otoliths were discarded. 



Validation of growth increments 



A subset (out of 1900 otohths u.sed for aging) of 927 (603 

 from CPFV and 324 from spearing) otoliths ranging from 

 1 to 44 growth increments was examined for edge analysis. 

 Formation of the translucent zone followed a seasonal pat- 

 tern for ail otoliths combined (Fig. 1). A translucent zone 

 developed from December through April, followed by an 

 opaque zone that developed from May to November Trans- 

 lucent zones in over 70% of the otoliths were completely 

 formed by 1 May (or 120 Julian days), and formation of 

 the opaque zone was complete by January in over 80%- of 

 the otoliths. From these results, we concluded that only 

 one translucent and one opaque zone formed during a cal- 

 endar year Because only one translucent zone was shown 



Jan 



Mar 



May Jul 



Month of the year 



Sep 



Nov 



Figure 1 



Percentage of blue rockfish (Sebastes mystinus) having a translucent 

 zone along the otolith edge in each month (n=927). 



to form each year, the annual periodicity of these zones 

 was established. To complete the validation at each age, 

 an edge analysis should be conducted for each age class 

 individually (Campana, 2001 ). There were enough samples 

 to conduct an edge analysis for females up to age 23 and 

 males to age 25, and, in all instances, only one opaque and 

 one translucent zone formed annually. Therefore, female 

 blue rockfish were validated up to 23 years and males up 

 to 25 years. 



The length of a fish at the conclusion of translucent 

 zone formation (determined from the edge analysis) was 

 calculated. The first translucent zone was calculated to be 

 complete on 1 May, one year after the assumed parturition 

 on 1 January, or 365 Julian days -i- 120 Julian days = 485 

 days from parturition. The relationship between date of 

 capture and FL was described with the linear equation: 

 FL=0.16 X (date of capture) + 30.9 (/i=99, r^=0.91; Fig. 2). 

 From this equation, a fish would be 108.5 mm FL at the 

 time of completion of the first translucent zone (1 May, one 

 year after parturition). 



The relationship between fish length and otolith di- 

 ameter (Fig. 3) was best described by the linear equation 

 otolith diameter (mm) = 0.02 x (mm FL) - 0.02 (rt=198, 

 r2=0.95). From this equation and a fish length of 108.5 mm 

 FL at the time of the first translucent zone completion, an 

 otolith diameter of 2.19 mm was the estimated size of the 

 predicted translucent zone. 



Diameters of the first and second translucent zones 

 (/!=509, df=508, P<0.001) and the second and third trans- 

 lucent zones (71=151, df= 150, P<0. 05) differed significantly. 

 From a comparison of first, second, and third translucent 

 zone diameters in the otoliths of all blue rockfish against 

 fish length, the average observed diameter for the first 

 translucent zone was 2.17 mm (Fig. 4), compared to the 

 estimated diameter of 2.19 mm (from the above equation), 

 the average observed diameter of the second zone was 



