Distribution of scattering layer in Korean Waters

            Zang Geun KIM, Young Min CHOI, Cha Soo Park and Young Seup KIM 
            National Fisheries Research and Development Institute (NFRDI)
 
          408-1 Sirang-ri, Kijang-eup, Kijang County, Pusan, 619-900, Korea 

   Scattering layers is  vastly distributed throughout the  waters off Korea. One 
of the  major problems  encountered in the  fisheries acoustic survey  in Korean   
waters is  that most of  fish schools  are mixed with  dense aggregation of  the 
scattering layers.
   Acoustic density,  distribution depth  and vertical  length of scattering  layers 
were measured in the east southern waters of Korea, December 1993. 
   About 70 %  of total relative density  came from the scattering  layers. They 
were located  in the water  layer of 30-300 m  with vertical length  of 2-100 m 
and descended  as bottom depth was  deeper up to about  200 m but  not below 
that depth. Predominant  species identified by mid-water trawl was   Maurolicus 
japonicus, mixed  in small portion with  Todarotus pacificus, Trichiurus lepturus 
and Pampus echinogaster. Dense aggregation of the layers was distributed along 
the under side  of thermocline (15 - 5  oC). Vertical length and relative  acoustic 
density of the layer was increased with increasing gradient of thermocline.