RESULTS 



Sampling 



A total of 683 trawls was taken during the 5 mo of combined 

 surveys (Table 8); 497 trawls were taken by the Miller Freeman, 

 Anna Marie, and Pat San Marie during April-June; 186 trawls 

 were taken by the Oregon for the 1976 Crab-Groundfish Survey 

 during May-August. Of the total 683 trawls, 19 were unsuccessful. 



Sampling activities were significantly influenced by the extreme 

 southerly distribution of sea ice in the eastern Bering Sea during 

 the winter of 1975-76. Pack ice limits during April-June 1976 were 

 at an extreme southern latitude compared to positions of the 

 pack edge in the same months, 1954-70 (Potocsky 1975). Late 

 pack ice breakup during spring 1976 also caused some delay in 

 survey coverage. 



During April 1976 pack ice extended south to approximately 

 lat. 56 °N, enclosing the Pribilof Islands and Port Moller. Trawl- 

 ing during April was restricted to stations north and northwest of 

 Unimak Island in deep water (Fig. 5). During May- June, the 

 areas of sampling progressed north and northeast, following the 

 open water exposed by pack ice recession (Fig. 6, 7). Subsequent 

 sampling during July-August was conducted along the outer 

 continental shelf north of Unimak Island to complete the Crab- 

 Groundfish Survey (Fig. 8, 9). 



The 664 successful trawls were assigned to three categories: 1) 

 435 grid stations that satisfied requirements for even spacing of 

 sampling locations within subareas, to be used for estimates of 

 population abundance; 2) 44 additional stations that were taken 

 at opportunities independent of the station grid, to supplement 

 the grid stations for distributional analyses; and 3) 185 other 

 trawls that included Crab-Groundfish Survey stations and 60 

 comparative trawls used only for vessel intercalibration and 

 specimen data collections. 



Catches during the spring survey were usually < 3,300 

 kg/trawl, but on a few occasions when large concentrations of 

 yellowfin sole were encountered they ranged from 5,300 to 23,000 

 kg/trawl. Of the 664 successful hauls taken by the four vessels, 

 only 177 (17.6%) were subsampled rather than completely pro- 

 cessed (Table 9). 



All subdivisions of the study area were sampled in the planned 

 station pattern, with the following exception: Because of rough 



bottom encountered in the slope subareas, particularly in subdivi- 

 sion 3 Slope, only 14 of the 29 intended station transects were 

 completed. A total of 51 successful trawls were taken in the slope 

 subareas. 



Distribution of Temperature 



Because sea surface and bottom water temperature distribu- 

 tions changed relatively rapidly during spring warming, it was 

 necessary to summarize the temperature data by individual months. 

 Unfortunately, temperature measurements were not taken at each 

 trawling station, and the percentage of stations with temperature 

 data (compared to the total number of trawls taken during each 

 month) were April, 65%; May, 40%; and June, 55%. Within 

 each month, the geographical areas for which temperature data 

 had been collected were, in some regions, extremely disjunct. 



During April, surface temperatures in the area surveyed (Fig. 

 10) ranged from -1.1° to +3.9°C, with a gradient of pro- 

 gressively decreasing temperature from the outer to inner con- 

 tinental shelf. Subzero surface temperatures prevailed to the east 

 and northeast near the pack ice edge, extending as far south as lat. 

 55°10'N. Bottom water temperatures ranged from -0.5° to 

 + 5.7°C and also showed progressive cooling towards the inner 

 shelf. Relatively warm bottom water ( + 3.0° to + 5.7 °C) occurred 

 in the southern region of the study area between water depths of 

 ca. 130-360 m. 



In May, as the survey progressed north and northeast following 

 recession of the pack ice, relatively cold (- 1.7° to +2.0°C) sur- 

 face and bottom water occurred throughout all of the eastern Be- 

 ring Sea continental shelf inside of approximately the 120 m 

 isobath (Fig. 11). Surface temperatures ranged from -1.4° to 

 + 4.0°C. Bottom water temperatures ranged from -1.7° to 

 + 6.8°C. As in April, wannest water temperatures were found 

 along the outer edge of the continental shelf. 



By June, both surface and bottom water had warmed in the in- 

 ner Bristol Bay shallows east of long. 162°-164°W (Fig. 12). 

 Overall, surface temperatures ranged from 0.0° to +6.6°C, with 

 a broad region of relatively warm water ( + 3° to +6°C) in cen- 

 tral Bristol Bay. Bottom water temperatures were also warmest 

 ( + 2 ° to + 5 °C) along the north shore of Bristol Bay, progressive- 

 ly cooling towards apparently residual cold ( - 1 .2 ° to - 0.3 °C) 

 water remaining in the central shelf region. 



Table 8. — Summary of sampling activities during Ihe 1976 Bering Sea surveys. 







Trawls included' 





Additional 









in spring 1976 



Other 



unsuccessful 





Survey 



Months 



station 



pattern 



trawls : 



trawls 



Total 



1976 spring trawl survey 



April 



112 



(106) 



6 



7 



125 



(Vessels Miller Freeman. 















Anna Marie, and Pat 



May- 



231 



(195) 



17 



9 



257 



San Marie) 



June 



_93 



( 91) 



20 



_2 



115 



Subtotal 





436' 



(392) 



43 



18 



497 



1976 crab-groundfish 















survey 



May 







( 0) 



14 







14 



(Vessel Oregon) 



June 



30 



( 30) 



47 







77 





July 



13 



( 13) 



48 



1 



62 





August 







( 0) 



33 



_u_ 



33 



Subtotal 





43 



( 43) 



142 



T 



!Si 



Total 





470 



(435) 



185 



19 



683 



Numbers without parentheses indicate total number of trawls. Numbers in parentheses indicate the 

 subset of grid stations used for biomass and population analyses. 

 'Includes 60 comparative trawls between Oregon and Pal San Marie. 



12 



