Brodziak and Mikus: Variation in life history parameters of Microstomus paaficus 



667 



area appeared to grow more slowly and achieve 

 greater sizes than females from the other areas. 

 Estimates of female L, and K from the Colum- 

 bia area were '2'7f and -24'/^ different from esti- 

 mates for the combined Vancouver, Eureka, 

 and Monterey areas (Table 3). As with the 

 results for males, female growth parameters 

 were more precisely estimated for the alterna- 

 tive gi-owth curve with CVs of 1-6''* in compar- 

 ison with CVs of 2-6.5'^f for the standard von 

 Bertalanffy curve. In contrast to males, residu- 

 als of female growth curves were normally dis- 

 tributed and there was an apparent increase 

 in L. with latitude. Overall, geographic varia- 

 tion of male and female growth was similar, 

 with the exception that asymptotic female size 

 appeared to increase with latitude. 



Maturation curves 



We found that male Dover sole matured at 

 smaller sizes than did females when samples 

 were combined across areas (Table 4). Pre- 

 dicted female median length at maturity (L50I 

 exceeded male Ljq by 6 cm (23%), and the ratio 

 of median length at maturity to asymptotic size 

 {L^g/Lj of females exceeded that of males by 

 14%. The estimate of male L,,, (CV=2%) was 

 more variable than the female Lgg (CV=1%). 



Maturity-at-age curves for all areas (Table 5) 

 indicated that males matured at younger ages 

 than females. Predicted female median age at 

 maturity ^A^^^) exceeded male A,,, by three years 

 (57%), whereas the ratio of female median age 

 at maturity to maximum obsei-ved age (^Ar,,/ 

 ^mnx^ exceeded that of males by about 42%. The 

 estimate of male Ar,„ (CV=109r ) was less precise 

 than the female estimate (CV=3%). 



Geographic variation was evident m matu- 

 rity at length by INPFC area (Fig. 3). The best 

 logistic model for maturity at length included 

 terms' for length, sex, area, length x sex, and 

 length X area and had a dispersion parameter 

 of = 1.28 (Table 4). This factor indicated a 

 moderate degree of overdispersion in the maturity-at- 

 length data. Male maturity curves by INPFC area showed 

 a geographic cline in L^q 

 decreased with latitude. Male L 



22 to 29 cm with CVs of 2% to 9%. Similarly, the ratio 

 Lr,f/L^ decreased from 0.66 in Monterey to 0.47 in Van- 

 couver Female L^q's showed a similar geographic cline. 

 although female Lg^'s were more precisely estimated than 

 male Lgg's. Female L^g values ranged from 35 cm in Mon- 

 terey to 28 cm in Vancouver Female values of Lj^/L also 

 decreased as latitude increased. Overall, median length 

 at maturity of both male and female Dover sole decreased 

 with increasing latitude. 



and median size at maturity 

 5Q values ranged from 



' AT denotes an interaction between A' and Y. 



Maturity at age also varied by INPFC area (Fig. 4). 

 The best logistic model included terms for age, sex, area, 

 age X sex. and age x area (Table 5). Dover sole maturity- 

 at-age data were highly overdispersed and the ratio of 

 observed-to-expected sampling variance for the selected 

 model was = 4.86. Male maturity ogives by INFPC 

 area suggested a latitudinal cline in Agg. Male Ag,, values 

 ranged from 3 to 7 years and decreased with increasing 

 latitude, except for the Columbia area. CVs of male Ag^ 

 values were high and ranged from 8% to 70%. The ratio 

 ^5(/^;ii(,v showed a clear latitudinal trend and decreased 

 from 0.22 in Monterey to 0.09 in Vancouver. Female Ag^ 

 values decreased as latitude increased and ranged from 9 

 years in Monterey to 6 years in Vancouver Estimates of 

 female Ag,, by INPFC area were more precise than those 

 for males (with CVs of 5-20%). Female ratios of Agf/A^j^,^. 



