Brodziak and Mikus; Variation in life history parameters of Microstomus pacificus 



665 



length was significantly greater than mean male length 

 for all areas combined and within each area (P<0.05). 

 Mean lengths were gi-eatest within the Eureka and Mon- 

 terey areas and smallest in the Vancouver area. The small- 

 est male ( 16 cm ) was 4 years old, whereas the two largest 

 males (51 cm) were 25 and 37 years old. The smallest 

 female (15 cm) was 2 years old and the largest female (66 

 cm) was 38 years old. 



Weight distributions differed by sex across areas. Mean 

 female weights exceeded male values by 200 to 300 g. 

 Significant differences between male and female weight 

 were detected for all areas combined and within each 

 area (P<0.05). Individual fish weights were more variable 

 for females than for males. Mean weights were greatest 

 within the Eureka and Monterey areas and lowest in the 

 Columbia area. The lightest male weighed 40 g and was 

 5 years old, whereas the heaviest male was 1325 g and 

 26 years old. The lightest female weighed 33 g and was 5 

 years old, whereas the heaviest female was 2479 g and 38 

 years old. 



Growth curves 



Variances in length at age of male and female Dover sole 

 were homogeneous. For male samples (?!=2613), the coef- 

 ficient of variation (CV) of length at age ranged from 6 

 to 14% and averaged 10%, with an average variance of 

 12.5 cm. Male variance in length was homogeneous across 

 ages (P=0.83, x-=20.97). For female samples (;?=2514), the 

 CV ranged from 6 to 16% and averaged 11%, with an aver- 

 age variance of 17.5 cm. Similar to that for males, female 

 variance in length was homogeneous across ages (P=0.59, 

 X-=25.64). As a result, we used an additive normal error 

 term for estimating gi'owth curves. 



There was sexual dimorphism in growth of Dover sole 

 when samples were pooled across areas. Maximum like- 

 lihood estimates and standard errors (SE) for pooled-sex 

 samples were as follows: L^,^^^ = 51.3 cm, SE = 0.5; L,„„, = 

 20.9 cm, SE = 0.3; c = 0.9337, SE = 0.0030 with correspond- 

 ing von Bertalanffy values: L^, = 52.6 cm, K = 0.069, and t^ 

 = -5.4. Male and female growth parameters for all areas 

 (Table 3) were significantly different (P<0.001, x-=1079) 

 and showed that females grow more rapidly than males 

 and attain larger sizes. There was greater variation in 

 female size at age, and residual variance from the female 

 cui-ve was roughly twice that value from the male curve. 

 Both female and male curves for samples pooled across 

 areas did not satisfy the assumption of normally distrib- 

 uted residuals (P<0.01). Thus, neither male nor female 

 growth was adequately described by a single growth cui"ve 

 representing all areas. 



Geographic variation was evident in male growth cui^ves 

 estimated for each area (Table 3). The hypothesis of identi- 

 cal growth parameters for all areas was rejected (P<0.001, 

 X^=96.25). Male samples from adjacent INPFC areas were 

 grouped and growth cui-ves were estimated. Homogeneous 

 growth was rejected for Vancouver and Columbia sam- 

 ples (P<0.001, x^=25.88) and for Columbia and Eureka 

 samples (P<0.001, X"=42.31) but was accepted for the 

 Eureka and Monterey samples (P=0.28, X"=3.85). Homo- 

 geneous growth was rejected for combined samples from 

 Eureka, Monterey, and Columbia (P<0.001, x-=80.98) but 

 was accepted for combined male samples from Eureka, 

 Monterey, and Vancouver (P=0.35, X"=6.65). 



We found that growth of male Dover sole differed 

 between the Columbia area and the combined Vancouver, 

 Eureka, and Monterey areas (Table 3) and that male 

 growth curves from the Vancouver, Eureka, and Monterey 



