Biomass estimation of walleye pollock (Theragra Chalcogramma) by the Echo 
  Integration and Midwater Trawl Survey in the Bering Sea during May!-June 1997

        Seok Gwan CHOI, Chul In BAIK, Won Seok YANG, Soon Song KIM,
                            Taeg Yun OH and Doo nam KIM

                 National Fisheries Research and Development Institute
                            Pusan 619-900, Republic of Korea

   For  the  biomass  estimation  of   the  Bering  Sea  walleye  pollock  (Theragra 
chalcogramma), an  echo integration and  midwater trawl  survey was carried  out in 
the area  from the Bogoslof  island region to  the international waters  of the Bering 
Sea (known as Donut Hole)  onboard the National Fisheries Research & Development 
Institute's research vessel Pusan 851 (in KOREA) during May!-June 1997.
   Acoustic  data was  collected from  SIMRAD EK500  Echo Sounder  (38kHz, split 
beam), VD500  Towing body adhere  to the 38kHz  split beam transducer  and BI500 
Echo  Integrator.  Midwater trawl  hauls  were  made  to identify  fish  species  and 
biological sampling at the selected location where a good echosign.
   Distribution density of walleye pollock was much higher in the continental shelf of 
the Eastern Bering Sea than in the other area.
   Fork length and  body weight composition of walleye pollock  caught by midwater 
trawl  hauls were  divided into  the  four areas:  eastern and  western  areas of  the 
Bogoslof Island area, the  middle area between Bogoslof island area and  High Sea of 
Bering Sea, the  continental shelf and slope of Eastern  Bering Sea, and High Sea  of 
Bering Sea.
   Based on the acoustic and biological data we collected, biomass of  walleye pollock 
in the whole  survey areas was estimated to  be 200,263 mt. For the  Bogoslof island 
area it was  13,274 mt, 17,795 mt for the  middle area, 157,098 mt for the  continental 
shelf and slope, and 12,096 mt for the  High Sea. In the continental shelf and slope it 
accounted for 78.4 % of the total estimated biomass.