Some investigation were performed on the industrial fisheries of tuna in Oman Sea in 1996. The result showed that the total fisheries of Spanish purse seiners, Montelape & Montealegre, were more than 8907 tons; yellow fin tuna (91%) and longtail tuna (9%) from March to September 1996. Their activity was in the Indian Ocean from September 1996 to March 1997. Using Jahadpozm longliner, 204 tons of tuna including yellow fin tuna (99.2%) and swordfish (< 1%) were fished in Oman Sea during a 9 month period in the years 1995 & 1996. The CPUE of these purse seiners were 40 tons per fishing day which was noticeable in comparison with 21 tons of purse seiners in the Indian Ocean and indicated the richness of EEZ of Oman Sea. Longtail tuna mostly were fished by Spanish vessels in western regions of 600 longitude and yellow fin tuna were caught from 57º to 62º longitudes in Oman Sea. Comparing the length distribution of yellow fin tuna caught by industrial and artisanal fisheries showed that the .....