Nichol: Annual and between-sex variability of Pleuronectes asper 
549 
Figure I 
Standard Alaska Fisheries Science Center eastern Bering Sea survey stations. Large numer- 
als (1-6) indicate strata areas: strata 1-2, <50 m; strata 3-4, 50-100 m; strata 5-6, 100-200 m. 
Materials and methods 
Surveys and gear 
Standard AFSC Owing to differences in standard 
trawl gear used prior to 1982, only the 1982-96 stan- 
dard surveys are considered here. About 350 stan- 
dard stations, ranging in depth from 16 m to 230 m, 
were sampled annually for each of the 1982-96 AFSC 
surveys (Fig. 1; Table 2). Survey stations were spaced 
37 km (20 nautical miles) apart, following a 37 x 37 
km grid pattern. Surveys generally began in inner 
Bristol Bay, followed transects directed north and 
south, and progressed east to west with each finished 
transect. Trawls were towed for about 30 min at a 
speed of 5.6 km/h (3 knots) at each station during 
daylight hours. The standard AFSC sampling gear, 
an 83-112 “eastern” trawl, was characterized by av- 
erage vertical and horizontal wing openings of 2.6 m 
and 16.5 m, respectively. Effective net spread and 
height measurements were obtained by means of a 
commercial trawl net-mensuration system (Scanmar) 
that was used during most tows. Footrope and 
headrope lengths were 25.3 m and 34.1 m, respec- 
tively. Paired 55-m dandylines (bridles) were at- 
tached to each wing and to 1.8 m x 2.7 m steel V- 
doors. Chain extensions measuring 61 cm in length 
were attached from each end of the footrope to the 
lower dandyline to improve bottom contact of the 
footrope. Two chartered commercial trawl vessels 
were employed each year to complete the standard 
survey. A total of 9 vessels ranging from 30.0 to 39.6 m 
in length have been used since 1982. 
Total yellowfin sole catch weights (kg) as well as 
random sex-specific length-frequency samples (total 
length in cm) were collected at each station (haul) 
where the species was captured. Haul positions, bot- 
tom depths, and surface and bottom temperatures 
were also recorded at each station. 
AFSC exploratory tows Additional 30-minute tows 
in waters nearer shore than the standard survey area 
were made during the course of the AFSC surveys 
with the same trawl gear and sampling procedures. 
Sampling depths ranged from 9.0 m nearshore to 
29.3 m offshore. A total of twenty-five nearshore tows, 
13 in the Togiak Bay area and 12 in the Kuskokwim 
Bay area, were made during the 1988-91 standard 
