824 



Fishery Bulletin 100(4) 



Figure 3 



The second ray of the first anal fin showing the location of the cross 

 section at a distance equal to a half of the width of the condyle base 

 above the base (A), and a section of the second ray of the first anal 

 fin(Bl. 



magnifications from 8x to 16x depending on the size of the 

 section. The clearest one of the three sections from each fin 

 ray was read three times by one reader about one to three 

 months apart with no knowledge of fish length. The pre- 

 cision of readings was evaluated as the average percent 

 error (APE, Beamish and Fournier, 1981) and coefficient 

 of variation (CV. Campana et al., 1995, 2001). For those 

 sections resulting in three different readings, each section 

 was reread by two to three readers simultaneously. Speci- 

 mens whose age estimates still disagreed were omitted 

 from further analyses. 



The images of the anal-fin ray sections were captured 

 by using an Image Analysis Software package (Media 

 Cybernetics. 1997) in combination with a dissecting mi- 

 croscope equipped with a charged coupled device (CCD) 

 camera (model: Toshiba IK-630) and a Pentium II com- 

 puter equipped with a 640 x 480 pixel frame grab card 

 and a 800 x 600 pixel monitor. The images were measured 

 in microns after distance calibrations were incorporated. 

 The distances from the focus to the distal edge of the sec- 

 tion (ray radius) and from the focus to the distal edge of 

 each growth band (annulus) were measured and recorded 



(Fig. 4). The focus, the growth band, and the false growth 

 band (multiple bands) were defined according to Berkeley 

 and Houde (1983), Tserpes and Tsimenides (1995), and 

 Ehrhardtetal.(1996). 



The marginal increment ratio (MIR), which was used 

 to validate the reading of annuli, was estimated for each 

 specimen by the following formula (Prince et al., 1988; 

 Esteves et al., 1995): 



M//? = (S-S„)/(S„-S„_i), 



where S = ray radius; and 



S and S , = the distance from ray focus to bands n and 

 n-1, respectively. 



The mean MIR and the standard deviation were computed 

 for each month by sex for all ages combined and also for 

 each age separately. 



Growth was analyzed by using the back-calculation of 

 length-at-age for each sex. For this purpose, a relation- 

 ship was determined between the ray radius and the 

 LJFL. This relationship and the distance from the focus 



