Wyanski et al : Growth, population age structure, and aspects of the reproductive biology of Epinephdus niveatus 



203 



Table 2 



Histological criteria used to determine reproductive stage in snowy grouper (see Hunter and Goldberg, 1980; Wallace and Selman, 

 1981; Hunter and Macewicz, 1985; Wenner et al., 1986; West, 1990). 



Reproductive stage 



Criteria 



Immature 



Developing 



Ripe 



Developing, recent spawning 



Spent 



Resting 



Uncertain maturity 

 Transitional 



Previtellogenic oocytes only, no evidence of atresia. In comparison with resting female, most previ- 

 tellogenic oocytes are <70 pm, area of transverse section of ovary is smaller, lamellae lack muscle 

 and connective tissue bundles and are not as elongate, oogonia are abundant along margin of 

 lamellae, and ovarian wall is thinner. 



Oocytes undergoing cortical granule (alveoli) formation through nucleus migration and partial 

 coalescence of yolk globules. 



Completion of yolk coalescence and hydration in the most advanced oocytes. Zona radiata becomes 

 thinner. 



Developing stage as described above plus presence of postovulatory follicles. 



More than 50% of vitellogenic oocytes in alpha or beta stage of atresia. 



Previtellogenic oocytes only with traces of atresia possible. In comparison with immature female, 

 most previtellogenic oocytes >70 pm, area of transverse section of ovary is larger, lamellae have 

 muscle and connective tissue bundles, lamellae are more elongate and convoluted, oogonia are less 

 abundant along margin of lamellae, and ovarian wall is thicker and exhibits varying degrees of 

 expansion owing to previous spawning. 



Immature or resting. Inactive ovaries, previtellogenic oocytes only. Reproductive stage is uncertain. 



Proliferation of spermatogonia through limited spermatogenesis within lamellae of resting ovary, 

 accompanied by development of peripheral sinuses in musculature of ovarian wall. 



readers couM not agree on the age or if the section 

 was not adequate. Ages ranged from 1 to 29 yr and 

 lengths from 226 to 1137 mm. From a subsample 

 (n=21A) of 3-10 yr old specimens, we found that 

 the mean width of the sagittal marginal translucent 

 zone was smallest in April and May, indicating the 

 period of increment formation ( Fig. 2 ). The unimodal 

 nature of the data indicated that one increment was 

 deposited per year. 



Data from longlines and snapper reels showed 

 that size at age was greater during 1993-94 than 

 during the previous decade (Figs. 3 and 4). Snowy 

 grouper captured with longlines in 1993-94 exhibited 

 a nearly constant growth rate until approximately 

 age 10, after which there was a notable decrease. 

 A similar growth pattern was noted for snowy gi-ou- 

 per caught with snapper reels, although the trend 

 was less definitive owing to smaller sample sizes. 

 Estimates of theoretical maximum length (Lj were 

 reasonable when compared with maximum observed 

 lengths (Table 3). Data from both gear types indi- 

 cated that L ., has increased 169-231 mm in the last 

 decade. The application of the age-length key for 

 samples caught with longlines during 1993-94 to 

 TIP length data for the same period revealed recruit- 

 ment to the fishery as early as age 1, and a modal 

 age for recruitment of 5 (Table 4). 



The increase in size at age since the 1980s was also 

 evident in comparisons of age-length keys between 



■Q 



80 

 075 

 70 

 65 

 0.60 

 55 



■a "^^ " 



S 



'•S 0.45 - 



■§ 



I 40 - 



35 - 



30 - 



25 



A 



"1 — r 

 ] J 



Month 



1^ 

 A 



-\ 1 \ 1 



O N D 



Figure 2 



Mean width (+SEl of marginal translucent zone in trans- 

 verse sections of sagittae from 248 snowy grouper that 

 were 3-10 yr old. 



periods for each gear type. For longline gear, the 

 comparisons in 8 of 8 length intervals exceeded the 

 adjusted significance level (P<0.00639; Table 5). The 



