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Fishery Bulletin 90(2). 1992 



reddish-blue in color, and very 

 soft in texture. Histologically, 

 the spent ovary displayed in- 

 creased vascularization, a thick- 

 ening of the tunica, and post- 

 ovulatory follicles undergoing 

 various stages of resorption (Fig. 

 4D). In addition, larvae remain- 

 ing after parturition and yolked 

 oocytes not reaching maturity 

 are frequently seen in various 

 stages of resorption. 



Late-recovering and early- 

 developing ovaries possessed 

 reorganized lamellar branches 

 containing Stages I, II, and early 

 Stage-Ill oocytes as resorption 

 nears completion (Fig. 4E). All 

 samples collected in April were 

 in this condition (Fig. 6), which 

 marked the end of one reproduc- 

 tive season and the beginning of 

 the next reproductive cycle. 



Discussion 



MJJASON D 



MONTH 

 Figure 6 



Percent distribution of ovarian maturation stages (derived from the most advanced oocyte 

 or embryonic stage categorized histologically) from monthly collections of Sebastes 

 Jlavidus; n is same as presented in Table 1. Ill = late perinucleolus, IV = early yolk, 

 V = late yolk, VI = migratory nucleus, VII = ovulation/fertilization, EC = early-celled 

 embryo, EB = embryonic body, EL = eyed-larvae, SP = spent. 



In the present study, I estab- 

 lished an oocyte/embryonic clas- 

 sification that allows rapid determination of a rockfish 

 population's status in the annual reproductive cycle. 

 The use of this staging system allows one to establish 

 oocyte frequency distributions and categorize ovaries 

 as to their seasonal development, both temporally and 

 spatially. This information, in turn, not only permits 

 interannual and interpopulational comparisons, but 

 may help reveal variations related to environmental 

 factors. 



Developmental events that occur in the oocytes of 

 Sebastes Jlavidus are similar to those described for 

 other teleosts with group-synchronous development 

 (see review by Wallace and Selman 1981). Embryo- 

 genesis and the basic reproductive patterns follow 

 observations reported for other members of the genus 

 Sebastes (Moser 1967a, Wyllie Echeverria 1987). Tem- 

 poral occurrence of reproductive events and seasonal 

 variations of these events differ within the genus 

 (Wyllie Echeverria 1987). 



In the present work, oocyte development in S. Jlavi- 

 dus has been categorized by separating oocyte growth 

 into seven distinct stages. Oogonia and early-peri- 

 nucleolus stages (Stages I and II, respectively) are 

 found in the ovaries throughout the year. These stages 

 appear to grow continuously, develop asynchronous- 

 ly, and, particularly in Stage-II cells, display a wide 



range of cell diameters. Development of unyolked 

 oocytes in S. jlavidus is similar to that described for 

 S. paucispinus (Moser 1967a, b). However, seasonal 

 occurrence of Stage-Ill oocytes differs between the 

 two species. Stage-Ill oocytes in S. jlavidus decline 

 rapidly in number as yolk accumulation (Stage IV) is 

 initiated. They are not observed again in the ovaries 

 until after parturition and the beginning of the 

 reorganization of the lamellar branches. While Moser 

 (1967a) did not suggest a staging classification scheme, 

 his descriptions for S. paucispinus included oocytes 

 corresponding to Stage III (in the present study). In 

 contrast to S. jlavidus, these oocytes occurred in 

 ovaries of S. paucispinus throughout the year (Moser 

 1967a). The temporal difference in occurrence of Stage- 

 Ill oocytes between these two species is most likely a 

 reflection of the number of broods produced annually. 

 Viviparous species producing more than one brood an- 

 nually require a reserve of Stage-Ill oocytes. In rock- 

 fish where two or more broods of young are produced 

 in one reproductive season, a second clutch of yolked 

 oocytes develops concurrently with the initial brood of 

 gestating embryos. Moser (1967a) reported the second 

 clutch of yolked oocytes to occur in S. paucispinus 

 when the initial brood had reached eye-lens formation. 

 A distinct seasonal absence of Stage-Ill oocytes, or a 



