532 



Fishery Bulletin 88 (3|. 1990 



6-mm-thick sample from the central portion of one lobe 

 of each gonad was embedded in paraffin, sectioned to 

 G-t^m thickness, stained with Mayer's haematoxylin 

 (Humason 1972) and eosin Y, and mounted for micro- 

 scopic examination. Additionally, sections of vitello- 

 genic ovaries fixed in Zenker's fluid were sectioned to 

 S-i^m thickness and stained with Heidenhain's azan 

 (Humason 1972), 



Eight classes of maturity (Table 1) were distinguished 

 based on the histological criteria of Wallace and Selman 

 (1981) and Hunter and Macewicz (1985) for oogenesis 

 and Grier (1981) and Grier et al. (1987) for spermato- 

 genesis. Recognition of oocyte atresia and rejuvenation 

 was important in determining whether a fish had pre- 

 viously spawned. Atretic oocytes were recognized by 

 degeneration of the zona radiata, nuclear membrane, 

 and yolk globules (Moe 1969. Wallace and Selman 1981, 



Hunter and Macewicz 1985). "Rejuvenation" is defined 

 as the development of oocytes that were held in an 

 advanced perinuclear stage of development since the 

 previous spawning season. These clutches of oocytes 

 in postspawn, recovering females exhibited a char- 

 acteristic dual cytoplasmic banding (Yamamoto 1956, 

 Howell 1983). 



Length at maturity was determined by grouping fish 

 by coast and sex into 50-mm intervals, determining the 

 percentage that were mature (> class 4) within each 

 interval, and estimating the length at which 50% of the 

 fish were mature by interpolating between interval 

 midpoints. Oocyte diameters, measured with an ocular 

 micrometer, were used to define the spawning season. 

 Only oocytes whose nuclei were included in the cross 

 section were measured, because these have been shown 

 to represent true oocyte diameters (Foucher and 



