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Fishery Bulletin 97(4), 1999 



c 

 d) 



3 

 CT 

 O 



October y '^Jm '^^:^7y '°°J^ STT^ '""J* 



PG CA VO LV HO ABPOF 



~l T 



PG CA VO LV HO ABPOF 



PG CA VO LV HO ABPOF 



PG CA VO LV HO ABPOF 



Oocyte developmental stage 



Figure 7 



Average frequency of occurrence of oocyte development stages by month for vermilion snapper from 

 the eastern Gulf of Mexico. PG=primary growth oocyte. CA=cortical alveolar oocyte, VO=vitellogenic 

 oocyte, LV=late vitellogenic oocyte, HO=hydrated oocyte, AB=atretic body, and POF=postovulatory 

 follicle. 



and agreement rates than scales or whole otoliths 

 can produce. Our readability rates were high (98%) 

 and were similar to rates reported by Zhao et al. 

 (1997), who were able to read 96% of sectioned 

 otoliths from SAB vermilion snapper. The use of 

 whole otoliths has produced mixed results. Barber 

 ( 1989) had a high agreement rate between readings 

 (84%) and was able to count as many as 26 zones. 

 However, Grimes (1978) found that whole otoliths 

 were difficult to interpret at ages greater than 7. 

 Scales have been used with limited success by Grimes 

 (1978), Zastrow (1984), Nelson (1988), and Collins 

 and Pinckney ( 1988). Agreement rates between read- 

 ings in these studies have ranged from 44% to 85% 

 and were lower than reported in this study ( 100% ) 

 and by Zhao et al. ( 1997 ) ( 96% ). Grimes ( 1978 ) found 

 that counts from scales and whole otoliths from the 

 same fish were similar and reported an agreement 

 rate of 75%. 



Marginal-increment analyses suggest that vermil- 

 ion snapper form one opaque band per year in the 

 late spring and summer. This pattern has also been 

 noted for vermilion snapper captured from the SAB. 

 Zhao et al. ( 1997 ) found that opaque zones formed in 



June for fish age one year and in July for fish ages 

 two to six years. Barber (1989) attempted to use 

 marginal-increment analyses to validate annulus 

 formation in whole otoliths from snapper from the 

 GOM; however, he was unable to show an annual 

 pattern. Grimes (1978) observed that the hyaline 

 layer was formed in November in the SAB. Because 

 hyaline and opaque bands alternate, Grimes's ( 1978) 

 findings imply that an opaque band is formed once a 

 year before November 



Vermilion snapper are considered long-lived, slow- 

 growing fish (Manooch, 1987). The oldest individual 

 we aged was 13 years old, similar to the SAB maxi- 

 mum age of 12 years reported by Zhao et al. (1997), 

 who also used sectioned otoliths. However, our maxi- 

 mum age was older than the scale-based maximum 

 ages reported for the western GOM of age 7 by 

 Zastrow (1984) and age 10 by Nelson (1988). Those 

 using scales to age fish typically underestimate the 

 ages of older fish (Beamish and McFarlane, 1987). 

 As fish approach their asymptotic size, little or no 

 increase in fish size occurs and this is reflected as 

 little or no increase in scale size. Therefore, rings at 

 the scale edge of older (larger) fish become difficult 



