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Fishery Bulletin 96(3), 1998 
yellowfin sole. However, because yellowfin sole males 
were dominant inshore and females were dominant 
offshore, the more likely cause for the sex-propor- 
tion patterns observed here was the differential dis- 
tribution patterns between sexes. 
Among-year variation 
Spring-summer distributions during 1982-84 may 
have been deeper than those in subsequent years, in 
part, because the population was younger and less 
mature. Wilderbuer et al. ( 1992) indicated that older 
( >17 years) yellowfin sole were an insignificant part 
of the population prior to the mid-1980s compared 
with later years and indeed, length distributions were 
skewed toward smaller length groups during the 
1982-84 surveys compared with later years (Fig. 6). 
Given estimated lengths at 50% maturity of 20.3 and 
28.8 cm TL for male and female yellowfin sole, re- 
spectively (Wilderbuer et al., 1992), many of the fish 
constituting the strong modes from 1982 to 1984 were 
sexually immature. Certainly there was a progres- 
sion from immaturity to maturity for many of these 
fish. Nichol (1997) showed that larger (25-32 cm) im- 
mature females nearing maturity maintain a deeper 
bathymetric distribution than mature spawning fish 
during spring-summer. With increasing maturity of 
the population, therefore, we would expect to see a 
distribution shift to shallower spawning waters in 
years after 1984. Smaller males (22-27 cm TL) and 
females (25-32 cm TL) constituted a large pro- 
portion of the yellowfin sole biomass from 1982 
to 1984 (Fig. 7). High concentrations of 22-27 cm 
males that resided at 40-49 m bottom depth dur- 
ing 1982-84 were not apparent from 1985 to 1996. 
Similarly, prominent modes of 25-32 cm females 
at 30-39 m and 70-79 m depths during 1982-84 
were not nearly as apparent during 1985-96 
(Fig. 7). 
Why then was the proportion of males within 
the standard area higher during 1982-83 than 
other years? The most plausible explanation is 
that the deeper overall yellowfin sole distribu- 
tions during these years rendered the population 
more available to the survey. Nearshore areas not 
Bottom depth (m) 
Figure 5 
Mean male proportions (no. males/no. males and 
females) of mature and immature yellowfin sole 
( Pleuronectes asper) by bottom depth during the 
1995 beam-trawl survey of Togiak Bay. Mean pro- 
portions are weighted by the CPUE (no. fish/hect- 
are) at each station within each depth grouping. 
Bars are 95% confidence intervals. 
