282 



Fishery Bulletin 90(2), 1992 



ages 1, 2, 3, and 4 were never altered by 

 more than 22 mm and the change was 

 generally less than 12 mm. The coefficient 

 of determination (r^) for the von Berta- 

 lanffy curve was 0.85 for both sexes using 

 individual lengths-at-age, and 0.93 for males 

 and 0.89 for females using the weighted procedure. 

 The respective parameters L^, K, and to in the von 

 Bertalanffy growth equations for males determined 

 using weighted data obtained from sectioned otoliths 

 overlapped those when the same approach was em- 

 ployed for whole otoliths, and the same was true for 

 K with females (Table 1, Fig. 8). The von Bertalanffy 

 growth-equation parameters using weighted data from 

 sectioned otoliths show that female P. speculator grow 

 towards a larger asymptotic size (L^) than males 

 (Table 1, Fig. 8). Individual lengths of P. speculator in 

 December-February at the end of their first and sec- 

 ond years of life were 190-310mm and 210-370mm, 

 respectively, for males, and 210-300 mm and 250-400 

 mm, respectively, for females (Fig. 8). 



Discussion 



Marginal increments 



Marginal increments of the otoliths of P. speculator 

 with two or more translucent zones exhibited con- 

 spicuous trends only after the otoliths were sectioned. 

 This is largely due to the fact that sectioning of otoliths 

 results in more accurate measurement of their periph- 

 eral and/or penultimate opaque zones, because one or 

 both of the two outermost translucent zones have 

 become more clearly delineated. This is similar to the 

 situation with starry flounder Platychthys stellatus, in 

 which annual trends in the marginal increments of 



600 



500 



Males 



E 



E 



00 



c 



00 



c 



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

 Age (years) 



Figure 8 



Von Bertalanffy growth curves fitted to length-at-age data, 

 weighted by the inverse of the sample size of each 0.1 year 

 age-group, using whole and sectioned otoliths of male and 

 female Platycephahts stpeculator. 



