Stanley and Kronlund: Life history characteristics for Sebastes brevispmis 



679 



similar between sexes as is common for most rockfishes 

 (Love et al., 1990). 



Lenarz and Wylie Echeverria's (1991) examination of 

 growth dimorphism led them to categorize rockfish as 

 demersal versus water column, and shallow (<125 m) 

 versus deepwater species (>125 m). Table 4 shows that 

 silvergray rockfish are consistent with other demersal 

 rockfish in that they show relatively little sexual dimor- 

 phism in growth. Lenarz and Wylie Echeverria (1991) 

 suggested that the size dimorphism may result from 

 trade-offs between fecundity and size; they suggest that 

 among water-column species, males may optimize size 

 solely for survival, whereas added size for a female may 

 confer advantages in egg production. 



Seasonal maturation and age at maturity 



The difficulties in the macroscopic staging of rockfish 

 maturity have been widely discussed (Gunderson et 

 al., 1980; Love and Westphal, 1981; Wyllie Echever- 

 ria, 1987; Love et al., 1990; Nichol and Pikitch, 1994). 

 These authors are consistent in suggesting that maturity 

 stages should be verified by histological examination of 

 samples collected through all seasons. 



More problematic than the staging is the possibil- 

 ity that commercial fishery samples may not be repre- 

 sentative of the overall population. If only the mature 

 fraction of an age class recruits to the fishery, then 

 age at maturity derived from commercial samples will 

 underestimate actual age at maturity. For the trawl 

 nets used in the rockfish fishery in British Columbia, 

 size at 100% retention for rockfish is about 30 cm. Sil- 

 vergray rockfish do not begin to recruit to the fishery 

 until about 35 cm; thus age or size at recruitment is 

 conditioned by behavior of the silvergray rockfish and 

 not by mesh size. 



Given the discussion above, our conclusions on age 

 and length at maturity should be viewed as tentative. 

 Nevertheless, the available observations indicate that 

 most females are mature by age nine and most males 

 by age nine or ten. Lenarz and Wylie Echeverria (1991) 

 noted that in 21 of 31 rockfish species, females and 

 males matured at similar ages. 



Mating appears to take place from September through 

 January and peaks from December through January. 

 This time range differs from the range derived from ob- 

 servations for southeastern Alaska where ripe male sil- 

 vergray rockfish were observed from January to March 



