2002 Volume 68 Issue sup1 Pages 93-96
Stock biomass of the Pacific stock of Scomber japonicus decreased from ca. 4-6 million tons during the early and mid 1970's to less than one million tons in the 1990's. This decline was probably caused from over-fishing and decreased reproductive success corresponding to regime shifts in the late 1970's and 1980's. We decided to keep the spawning stock biomass (SSB) above 0.45 million tons, because 1) no recruitment failures were observed above this level and 2) this SSB can be attained by preserving dominant year classes until their maturation (age-3). Problems of the allowable biological catch determination method in Japan were discussed and a practical solution was presented.