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Fishery Bulletin 103(4) 



premature-stage oocytes and POFs began to occur in 

 September. The composition of oocytes observed during 

 this month was divided into three groups: premature, 

 maturing, and postmature oocytes. In October, almost 

 all ovaries (96.2%) contained POFs. Of these, 28.0% 

 also contained oocytes at the tertiary yolk stage or 

 migratory-nuclear stage (or at both stages) and the 

 remaining 72.0% contained primary-yolk stage or less 

 advanced stage oocytes (or both of these stages). From 

 November to December, all ovaries contained POFs and 

 only a few (3.7% in November and 5.3% in December) 

 also contained vitellogenic oocytes. Therefore, almost all 

 individuals had finished spawning by October, although 

 a few continued to spawn until December. 



Atretic oocytes were found in samples throughout the 

 year, except February, in ovaries of various maturity 

 phases. Frequency of occurrence was highest in May, 

 and gradually decreased until the spawning season 

 (Table 3). Oocytes that ovulated but remained in the 

 ovigenous folds and were resorbed later were treated 

 as atretic oocytes because it was difficult to distinguish 

 between them and atretic oocytes if they were somewhat 

 absorbed. Atretic oocytes did not always correspond to 

 the most advanced oocytes in the ovaries. They occupied 

 0.3-1.8% (mean ±SD = 1.0 ±0.5) of the yolked, advanced 

 oocytes observed in the ovaries in May (the number of 

 oocytes counted in 10 ovaries ranged from 117 to 615), 

 and from 0.4 to 1.8% (1.0 ±0.4) of those observed in 

 August (range: 108-383 oocytes in 10 ovaries). 



Body length and age at first maturity 



The relationship between SL or age and maturity 

 of the fish caught between the prespawning month 

 (August) and the late-spawning month (December) was 

 examined. Otolith growth increments were counted for 

 all specimens. Because the spawning season occurs 

 from September to December, the birth dates of all 

 fish were conveniently defined as 1 January; age was 

 then determined accordingly. SL ranged from 114 to 

 237 mm (;? = 189, 170.6 ±25.3) and age, from 1 to 8 + 

 years (2.8 ±1.4). Individuals grew steeply until 2 years 

 and moderately until 6 years, after which time their 

 growth was slow (Fig. 4). All females whose ages were 

 estimated at more than 2+ years (n=152) were iden- 

 tified as maturing or spent-stage females. Only one 

 1+ year-old specimen (131 mm SL) was classified as 

 immature, whereas the other 1+ specimens (?i=36, 140.0 

 ±11.8) were classified as maturing or postmaturation 

 females (Fig. 4). 



Potential fecundity 



The diameters of oocytes in late vitellogenic maturity 

 phase ovaries were measured because potential fecun- 

 dity was determined as occurring before this maturity 

 phase. Oocytes ranged in diameter from less than 100 

 to 950 f*m and were separated into a small (less than 

 200 ;im) or large group (larger than 300 ^m, Fig. 5). 



