548 
Fishery Bulletin 96(3), 1 998 
Table 1 
Standard AFSC survey yellowfin sole ( Pleuronectes asper) biomass and population estimates, percentage of male and female 
CPUE (kg/hectare) in nearshore ( <30 m bottom depth) waters, sex-proportions, and mean CPUE-weighted bottom depths by sex, 
for years 1982-96. Commercial catch estimates for yellowfin sole in the eastern Bering Sea are also included. 
Year 
Survey 
biomass 
(metric tons) 
% CPUE ; < 30 m 
Population 
numbers 
(billions) 
Proportion 
male 
(m/m+f) 2 
Mean depth (m) 3 
Commercial 
catch 
(metric tons) 4 
Males 
Females 
Males 
Females 
1982 
3,377,838 
20.56 
9.81 
20.67 
0.492 
45.0 
52.9 
95,712 
1983 
3,535,269 
22.04 
5.41 
16.94 
0.486 
46.3 
58.5 
108,385 
1984 
3,141,188 
16.96 
5.62 
14.26 
0.434 
47.3 
58.7 
159,526 
1985 
2,443,666 
29.63 
11.39 
10.60 
0.437 
43.3 
55.2 
227,107 
1986 
1,909,866 
31.05 
13.38 
7.96 
0.436 
42.8 
54.7 
208,597 
1987 
2,613,067 
27.47 
13.18 
10.35 
0.438 
44.6 
53.6 
181,428 
1988 
2,402,369 
23.94 
9.86 
10.09 
0.426 
45.0 
55.6 
223,156 
1989 
2,316,249 
28.83 
20.05 
9.66 
0.454 
42.3 
48.3 
153,165 
1990 
2,183,708 
24.30 
12.46 
9.06 
0.435 
44.6 
53.0 
83,970 
1991 
2,393,268 
19.22 
5.94 
9.54 
0.453 
44.5 
53.8 
115,842 
1992 
2,172,900 
34.89 
19.01 
8.21 
0.452 
42.3 
53.4 
149,569 
1993 
2,465,443 
31.64 
11.59 
10.03 
0.442 
43.8 
54.2 
106,101 
1994 
2,610,474 
32.34 
13.73 
10.70 
0.442 
40.1 
51.0 
144,544 
1995 
2,009,671 
33.02 
13.66 
8.24 
0.445 
40.2 
51.3 
124,740 
1996 
2,298,560 
31.28 
9.83 
9.62 
0.460 
43.9 
56.8 
129,659 
1 %CPUE=(ICPUE, ( , <30 )/ICPUE, i;=d/; ) x 100 where CPUE,^ = station CPUE of the ith sex within the dth depth range. Note that this estimate is 
derived from the AFSC survey which did not cover the entire nearshore area. 
2 Proportion male = population number of males divided by population number of males and females. 
3 Mean depths are weighted by CPUE (kg/hectare) values at each tow location. 
4 Total retained and discarded catch estimates for yellowfin sole from foreign ( 1982-87), joint-venture (1982-90), and domestic (1987-present) 
fisheries in the eastern Bering Sea ( Wilderbuer 1 ). 
tions are inconsistent with age-structured stock syn- 
thesis models (Methot, 1990) that predict relatively 
stable abundance levels after 1981 (Wilderbuer 1 ). 
Large scale spring-summer Alaska Fisheries Sci- 
ence Center (AFSC) resource assessment surveys of 
the eastern Bering Sea shelf began with a baseline 
survey in 1975 (Pereyra et al. 2 ) and have continued 
annually since 1979 with the primary purpose of es- 
timating the abundance of important groundfish and 
crab species, including yellowfin sole (Gunderson, 
1993). In 1982, a change in the standard survey trawl 
from a 400-mesh “eastern” trawl to a larger 83-112 
“eastern,” increased the catch efficiency for most flat- 
fish species including yellowfin sole (Bakkala, 1993). 
Survey gear has remained constant since 1982. Al- 
1 (continued, from previous page) report for the groundfish re- 
sources of the Bering Sea/Aleutian Islands region as projected 
for 1997. North Pacific Fishery Management Council, 605 W. 
4 th Avenue Suite 306, Anchorage, AK 99501. 
2 Pereyra, W. T., J. E. Reeves, and R. G. Bakkala. 1976. Dem- 
ersal fish and shellfish resources of the eastern Bering Sea in 
the baseline year 1975. Northwest and Alaska Fisheries Cen- 
ter Proc. Rep. NOAA-NMFS, 619 p. Alaska Fisheries Science 
Center, Natl. Mar. Fish. Serv., NOAA, 7600 Sand Point Way 
NE, Seattle, WA 98115-0070. 
though these surveys cover most of the shelf area 
north of the Alaska Peninsula and south of latitude 
60°N (Fig. 1), nearshore waters have been excluded 
owing to shallow bottom depths and variable bottom 
substrate. Areas such as Togiak Bay (Fig. 1), where 
commercial trawlers have successfully targeted yel- 
lowfin sole in waters as shallow as 5-6 m (Low and 
Narita, 1990), have been excluded from resource as- 
sessment. Recognition that yellowfin sole spawn 
during the survey period (June-August) and that 
nearshore spawning grounds extend into these 
nonsurveyed areas (Nichol, 1995) has prompted 
speculation as to whether fluctuations in survey bio- 
mass may be due to annual variation in yellowfin 
sole distributions that overlap surveyed and 
nonsurveyed areas. 
This study investigates two potential sources of 
variation in yellowfin sole distribution during spring- 
summer, which may partially account for fluctuations 
in survey biomass estimates. In this paper, I describe 
variations in yellowfin sole distribution patterns be- 
tween sexes and among years. Data from exploratory 
nearshore samples are included to demonstrate prob- 
lems associated with the exclusion of nearshore ar- 
eas from resource assessments. 
