Nichol: Effects of geography and bathymetry on growth and maturity of Pleuronectes asper 
497 
Age at maturity Analysis of female age at matu- 
rity was treated in the same manner as with length 
at maturity, substituting age (A) in years for length 
(L). Owing to smaller sample sizes (Table 2), data 
for years 1992-94 were pooled. 
Results 
Length at age 
The general effects of area and bottom depth on 
length at age were highly significant for both males 
and females (Table 3). Mean length-at-age plots for 
both male and female yellowfin sole indicated greater 
45 
Males 
E 
o 
or 
c 
CD 
45 
40 
35 
30 
25 
20 
15 
10 
Females 
ss 
l2 
5 
i 
■ 
• NW n = 2,483 
I 
» SE n = 2,726 
s 
1 ' ' 1 1 1 I ’ i i ' I 
o 5 10 15 20 25 30 
Age (yr) 
Figure 2 
Comparison of male and female yellowfin sole mean length 
at age between northwest (NW) and southeast (SE) areas 
of the eastern Bering Sea (1982-94). Error bars indicate 
95% confidence intervals. 
sizes at age in the northwest than in the southeast 
area of the eastern Bering Sea shelf (Fig. 2). Male 
and female yellowfin sole were on average 1.22 and 
1.02 cm larger at age, respectively, in the northwest 
area than in the southeast area. Average length-at- 
age differences between areas (northwest-southeast) 
increased with increasing age to more than 2 cm for 
both males and females (Fig. 3). Total lengths were 
generally greater at age in deeper (>50 m) waters 
than in shallow waters (<50 m) for males and females 
less than 8 and 9 years of age, respectively (Fig. 3). 
Length at maturity 
Female yellowfin sole lengths corresponding to 50% 
maturity (L 50 ) were greater in the northwest than in 
the southeast area, and L 50 increased with increas- 
ing bottom depth (Fig. 4). Area accounted for a 2.3 
cm female length-at-maturity difference (P=0.0001) 
in 1993 and a 0.91 cm difference (P=0.049) in 1994 
(Fig. 4; Table 4). Female L 50 increased with increas- 
ing bottom depth (P<0.013), varying by as much as 4 
cm between shallow and deeper waters (Fig. 4; Table 
4). Annual variation ( 1992-94) in L 50 appeared to be 
approximately 1 cm (Fig. 4). 
Age at maturity 
In contrast to length-at-maturity results, no signifi- 
cant age-at-maturity difference (P=0.080) was found 
for females between the two areas (Fig. 5; Table 5). A 
similar increase in female age at maturity, however, 
did occur with increasing bottom depth (P=0.0001), 
with age at 50% maturity increasing by 3 years from 
shallow to deeper waters (Fig. 5). 
Discussion 
Larger northwest fish lengths corresponding to a 
particular age or percent maturity, combined with 
no apparent age-at-maturity difference between ar- 
eas, indicate faster yellowfin sole growth in the north- 
west area than in the southeast area. Bottom depth 
effects on length-at-age, length-at-maturity, and age- 
at-maturity estimates, however, were more the re- 
sult of sampling uneven fish distributions, as dis- 
cussed below. 
Area effects 
The length-at-age and length-at-maturity differences 
found between areas support the hypothesis that 
northwest and southeast complexes are functionally 
allopatric during the summer spawning period. Tag- 
