FISHERY BULLETIN: VOL. 79, NO. 3 



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m m JULY AU6 SEP 

 MONTH 



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Figure 2.— Monthly percentages of 1- to 3-yr-old olive rockfish 

 with opaque margins. Sample size is in parentheses. 



the beginnings of the transparent zone during the 

 fall are readily apparent. 



Lengths at ages were estimated by direct obser- 

 vation of otolith annuli, back calculation of an- 

 nuli, and through the von Bertalanffy growth 

 curve model. In this model, the formula 



Lt = Ly,[l - exp -k(t - to)] 



where Lt = length at time t 



L -,_ - theoretical maximum length 

 k = constant expressing the rate of ap- 

 proach to L y, 



to = theoretical age at which Lt = 



was fitted to the direct observation age-length 

 data. 



We transformed the male and female von 

 Bertalanffy growth equations to linear form 

 (Allen 1976) and compared these by analysis 

 of variance. Females were found to grow signifi- 

 cantly faster than males if = 19.08, P<0.01), 

 hence we have separated growth data by sex 

 (Table 2). 



Mean lengths at ages obtained by direct obser- 

 vations of annuli and as generated by the von 

 Bertalanffy equations are plotted to age 14 (Figure 

 3). Through direct observation of annuli, we found 



536 



FEMtlES 



1 2 3 4 5 6 7 8 9 10 11 12 13 14 



UE ITEARSI 



Figure 3.— Von Bertalanffy growth curves of female (circles) 

 and male (triangles) olive rockfish. Also included are mean 

 lengths at ages (females — stars, males — dots) computed from 

 direct observation of otolith annuli. Based on 320 females and 

 296 males taken off Diablo Cove, 1972-77. 



a few individuals to live to be as much as 25 yr. 

 However, our samples of fishes older than about 

 14 yr were few, and older fish played little part 

 in growth calculations. Back-calculated lengths 

 (Tables 3, 4) were computed to age 12. Otoliths of 

 fish older than 12 3^^ were often unusable for back 

 calculations, because these fish laid down heavy 

 layers of opaque material along the axis used to 

 measure annuli, making measurements difficult. 



All three measures of growth yielded similar 

 results. Mean lengths at age for females and males 

 were similar through age 4. Females outgrew 

 males beginning at age 5, the age at which over 

 50% of the males were mature. Both male and 

 female olive rockfish had k values (0.27 and 

 0.18, respectively) higher than most previously 

 studied rockfish, indicating that the species 

 reached maximum length relatively quickly. The 

 /e-values were similar (though slightly higher for 

 both sexes) to those of S. flavidus (Fraidenburg 

 1980; Westrheim and Harling footnote 4), a closely 

 related species. 



Because few individuals older than 14 yr were 

 captured, estimates of length at age of older fish 

 produced by the von Bertalanffy equation may be 

 inaccurate. Certainly the L^'s are too low, as 



